X-Git-Url: http://git.indexdata.com/?p=idzebra-moved-to-github.git;a=blobdiff_plain;f=doc%2Fadministration.xml;h=b95db6619112ccf3c6a809d3822e27eec6e4b30b;hp=ccb156f56567693a1d335483455679bff2fd23cf;hb=HEAD;hpb=a31f9b2d25006c89ae7e9fb5870c0d222ee88a3a diff --git a/doc/administration.xml b/doc/administration.xml index ccb156f..b95db66 100644 --- a/doc/administration.xml +++ b/doc/administration.xml @@ -1,3430 +1,1880 @@ - -Quick Start - - -In this section, we will test the system by indexing a small set of sample -GILS records that are included with the software distribution. Go to the -test/gils subdirectory of the distribution archive. There you will -find a configuration -file named zebra.cfg with the following contents: - - -# Where are the YAZ tables located. -profilePath: ../../../yaz/tab ../../tab - -# Files that describe the attribute sets supported. -attset: bib1.att -attset: gils.att - - - - - -Now, edit the file and set profilePath to the path of the -YAZ profile tables (sub directory tab of the YAZ distribution -archive). - - - -The 48 test records are located in the sub directory records. -To index these, type: - - -$ ../../index/zebraidx -t grs.sgml update records - - - - - -In the command above the option -t specified the record -type — in this case grs.sgml. The word update followed -by a directory root updates all files below that directory node. - - - -If your indexing command was successful, you are now ready to -fire up a server. To start a server on port 2100, type: - - -$ ../../index/zebrasrv tcp:@:2100 - - - - - -The Zebra index that you have just created has a single database -named Default. The database contains records structured according to -the GILS profile, and the server will -return records in either either USMARC, GRS-1, or SUTRS depending -on what your client asks -for. - - - -To test the server, you can use any Z39.50 client (1992 or later). For -instance, you can use the demo client that comes with YAZ: Just cd to -the client subdirectory of the YAZ distribution and type: - - - - - -$ client tcp:localhost:2100 - - - - - -When the client has connected, you can type: - - - - - -Z> find surficial -Z> show 1 - - - - - -The default retrieval syntax for the client is USMARC. To try other -formats for the same record, try: - - - - - -Z>format sutrs -Z>show 1 -Z>format grs-1 -Z>show 1 -Z>elements B -Z>show 1 - - - - - -NOTE: You may notice that more fields are returned when your -client requests SUTRS or GRS-1 records. When retrieving GILS records, -this is normal - not all of the GILS data elements have mappings in -the USMARC record format. - - - -If you've made it this far, there's a good chance that -you've got through the compilation OK. - - - - - -Administrating Zebra - - -Unlike many simpler retrieval systems, Zebra supports safe, incremental -updates to an existing index. - - - -Normally, when Zebra modifies the index it reads a number of records -that you specify. -Depending on your specifications and on the contents of each record -one the following events take place for each record: - - - -Insert - - -The record is indexed as if it never occurred -before. Either the Zebra system doesn't know how to identify the record or -Zebra can identify the record but didn't find it to be already indexed. - - - - -Modify - - -The record has already been indexed. In this case -either the contents of the record or the location (file) of the record -indicates that it has been indexed before. - - - - -Delete - - -The record is deleted from the index. As in the -update-case it must be able to identify the record. - - - - - - - -Please note that in both the modify- and delete- case the Zebra -indexer must be able to generate a unique key that identifies the record in -question (more on this below). - - - -To administrate the Zebra retrieval system, you run the -zebraidx program. This program supports a number of options -which are preceded by a minus, and a few commands (not preceded by -minus). - - - -Both the Zebra administrative tool and the Z39.50 server share a -set of index files and a global configuration file. The -name of the configuration file defaults to zebra.cfg. -The configuration file includes specifications on how to index -various kinds of records and where the other configuration files -are located. zebrasrv and zebraidx must -be run in the directory where the configuration file lives unless you -indicate the location of the configuration file by option --c. - - - -Record Types - - -Indexing is a per-record process, in which either insert/modify/delete -will occur. Before a record is indexed search keys are extracted from -whatever might be the layout the original record (sgml,html,text, etc..). -The Zebra system currently supports two fundamantal types of records: -structured and simple text. -To specify a particular extraction process, use either the -command line option -t or specify a -recordType setting in the configuration file. - - - - - -The Zebra Configuration File - - -The Zebra configuration file, read by zebraidx and -zebrasrv defaults to zebra.cfg unless specified -by -c option. - - - -You can edit the configuration file with a normal text editor. -parameter names and values are seperated by colons in the file. Lines -starting with a hash sign (#) are treated as comments. - - - -If you manage different sets of records that share common -characteristics, you can organize the configuration settings for each -type into "groups". -When zebraidx is run and you wish to address a given group -you specify the group name with the -g option. In this case -settings that have the group name as their prefix will be used -by zebraidx. If no -g option is specified, the settings -with no prefix are used. - - - -In the configuration file, the group name is placed before the option -name itself, separated by a dot (.). For instance, to set the record type -for group public to grs.sgml (the SGML-like format for structured -records) you would write: - - - - - -public.recordType: grs.sgml - - - - - -To set the default value of the record type to text write: - - - - - -recordType: text - - - - - -The available configuration settings are summarized below. They will be -explained further in the following sections. - - - - - - -group.recordType[.name] - - -Specifies how records with the file extension name should -be handled by the indexer. This option may also be specified -as a command line option (-t). Note that if you do not -specify a name, the setting applies to all files. In general, -the record type specifier consists of the elements (each -element separated by dot), fundamental-type, -file-read-type and arguments. Currently, two -fundamental types exist, text and grs. - - - - -group.recordId - - -Specifies how the records are to be identified when updated. See -section . - - - - -group.database - - -Specifies the Z39.50 database name. - - - - -group.storeKeys - - -Specifies whether key information should be saved for a given -group of records. If you plan to update/delete this type of -records later this should be specified as 1; otherwise it -should be 0 (default), to save register space. See section -. - - - - -group.storeData - - -Specifies whether the records should be stored internally -in the Zebra system files. If you want to maintain the raw records yourself, -this option should be false (0). If you want Zebra to take care of the records -for you, it should be true(1). - - - - -register - - -Specifies the location of the various register files that Zebra uses -to represent your databases. See section -. - - - - -shadow - - -Enables the safe update facility of Zebra, and tells the system -where to place the required, temporary files. See section -. - - - - -lockDir - - -Directory in which various lock files are stored. - - - - -keyTmpDir - - -Directory in which temporary files used during zebraidx' update -phase are stored. - - - - -setTmpDir - - -Specifies the directory that the server uses for temporary result sets. -If not specified /tmp will be used. - - - - -profilePath - - -Specifies the location of profile specification files. - - - - -attset - - -Specifies the filename(s) of attribute set files for use in -searching. At least the Bib-1 set should be loaded (bib1.att). -The profilePath setting is used to look for the specified files. -See section - - - - -memMax - - -Specifies size of internal memory to use for the zebraidx program. The -amount is given in megabytes - default is 4 (4 MB). - - - - - - - - - -Locating Records - - -The default behaviour of the Zebra system is to reference the -records from their original location, i.e. where they were found when you -ran zebraidx. That is, when a client wishes to retrieve a record -following a search operation, the files are accessed from the place -where you originally put them - if you remove the files (without -running zebraidx again, the client will receive a diagnostic -message. - - - -If your input files are not permanent - for example if you retrieve -your records from an outside source, or if they were temporarily -mounted on a CD-ROM drive, -you may want Zebra to make an internal copy of them. To do this, -you specify 1 (true) in the storeData setting. When -the Z39.50 server retrieves the records they will be read from the -internal file structures of the system. - - - - - -Indexing with no Record IDs (Simple Indexing) - - -If you have a set of records that are not expected to change over time -you may can build your database without record IDs. -This indexing method uses less space than the other methods and -is simple to use. - - - -To use this method, you simply omit the recordId entry -for the group of files that you index. To add a set of records you use -zebraidx with the update command. The -update command will always add all of the records that it -encounters to the index - whether they have already been indexed or -not. If the set of indexed files change, you should delete all of the -index files, and build a new index from scratch. - - - -Consider a system in which you have a group of text files called -simple. That group of records should belong to a Z39.50 database -called textbase. The following zebra.cfg file will suffice: - - - - - -profilePath: /usr/local/yaz -attset: bib1.att -simple.recordType: text -simple.database: textbase - - - - - -Since the existing records in an index can not be addressed by their -IDs, it is impossible to delete or modify records when using this method. - - - - - -Indexing with File Record IDs - - -If you have a set of files that regularly change over time: Old files -are deleted, new ones are added, or existing files are modified, you -can benefit from using the file ID indexing methodology. Examples -of this type of database might include an index of WWW resources, or a -USENET news spool area. Briefly speaking, the file key methodology -uses the directory paths of the individual records as a unique -identifier for each record. To perform indexing of a directory with -file keys, again, you specify the top-level directory after the -update command. The command will recursively traverse the -directories and compare each one with whatever have been indexed before in -that same directory. If a file is new (not in the previous version of -the directory) it is inserted into the registers; if a file was -already indexed and it has been modified since the last update, -the index is also modified; if a file has been removed since the last -visit, it is deleted from the index. - - - -The resulting system is easy to administrate. To delete a record you -simply have to delete the corresponding file (say, with the rm -command). And to add records you create new files (or directories with -files). For your changes to take effect in the register you must run -zebraidx update with the same directory root again. This mode -of operation requires more disk space than simpler indexing methods, -but it makes it easier for you to keep the index in sync with a -frequently changing set of data. If you combine this system with the -safe update facility (see below), you never have to take your -server offline for maintenance or register updating purposes. - - - -To enable indexing with pathname IDs, you must specify file as -the value of recordId in the configuration file. In addition, -you should set storeKeys to 1, since the Zebra -indexer must save additional information about the contents of each record -in order to modify the indices correctly at a later time. - - - -For example, to update records of group esdd located below -/data1/records/ you should type: - - -$ zebraidx -g esdd update /data1/records - - - - - -The corresponding configuration file includes: - - -esdd.recordId: file -esdd.recordType: grs.sgml -esdd.storeKeys: 1 - - - - - -Important note: You cannot start out with a group of records with simple -indexing (no record IDs as in the previous section) and then later -enable file record Ids. Zebra must know from the first time that you -index the group that -the files should be indexed with file record IDs. - - - -You cannot explicitly delete records when using this method (using the -delete command to zebraidx. Instead -you have to delete the files from the file system (or move them to a -different location) -and then run zebraidx with the update command. - - - - - -Indexing with General Record IDs - - -When using this method you construct an (almost) arbritrary, internal -record key based on the contents of the record itself and other system -information. If you have a group of records that explicitly associates -an ID with each record, this method is convenient. For example, the -record format may contain a title or a ID-number - unique within the group. -In either case you specify the Z39.50 attribute set and use-attribute -location in which this information is stored, and the system looks at -that field to determine the identity of the record. - - - -As before, the record ID is defined by the recordId setting -in the configuration file. The value of the record ID specification -consists of one or more tokens separated by whitespace. The resulting -ID is -represented in the index by concatenating the tokens and separating them by -ASCII value (1). - - - -There are three kinds of tokens: - - - -Internal record info - - -The token refers to a key that is -extracted from the record. The syntax of this token is -( set , use ), where set is the -attribute set name use is the name or value of the attribute. - - - - -System variable - - -The system variables are preceded by - - -$ - - and immediately followed by the system variable name, which -may one of - - - -group - - -Group name. - - - - -database - - -Current database specified. - - - - -type - - -Record type. - - - - - - - - -Constant string - - -A string used as part of the ID — surrounded -by single- or double quotes. - - - - - - - -For instance, the sample GILS records that come with the Zebra -distribution contain a unique ID in the data tagged Control-Identifier. -The data is mapped to the Bib-1 use attribute Identifier-standard -(code 1007). To use this field as a record id, specify -(bib1,Identifier-standard) as the value of the -recordId in the configuration file. -If you have other record types that uses the same field for a -different purpose, you might add the record type -(or group or database name) to the record id of the gils -records as well, to prevent matches with other types of records. -In this case the recordId might be set like this: - - -gils.recordId: $type (bib1,Identifier-standard) - - - - - -(see section -for details of how the mapping between elements of your records and -searchable attributes is established). - - - -As for the file record ID case described in the previous section, -updating your system is simply a matter of running zebraidx -with the update command. However, the update with general -keys is considerably slower than with file record IDs, since all files -visited must be (re)read to discover their IDs. - - - -As you might expect, when using the general record IDs -method, you can only add or modify existing records with the update -command. If you wish to delete records, you must use the, -delete command, with a directory as a parameter. -This will remove all records that match the files below that root -directory. - - - - - -Register Location - - -Normally, the index files that form dictionaries, inverted -files, record info, etc., are stored in the directory where you run -zebraidx. If you wish to store these, possibly large, files -somewhere else, you must add the register entry to the -zebra.cfg file. Furthermore, the Zebra system allows its file -structures to -span multiple file systems, which is useful for managing very large -databases. - - - -The value of the register setting is a sequence of tokens. -Each token takes the form: - - -dir:size. - - -The dir specifies a directory in which index files will be -stored and the size specifies the maximum size of all -files in that directory. The Zebra indexer system fills each directory -in the order specified and use the next specified directories as needed. -The size is an integer followed by a qualifier -code, M for megabytes, k for kilobytes. - - - -For instance, if you have allocated two disks for your register, and -the first disk is mounted -on /d1 and has 200 Mb of free space and the -second, mounted on /d2 has 300 Mb, you could -put this entry in your configuration file: - - -register: /d1:200M /d2:300M - - - - - -Note that Zebra does not verify that the amount of space specified is -actually available on the directory (file system) specified - it is -your responsibility to ensure that enough space is available, and that -other applications do not attempt to use the free space. In a large production system, -it is recommended that you allocate one or more filesystem exclusively -to the Zebra register files. - - - - - -Safe Updating - Using Shadow Registers - - -Description - - -The Zebra server supports updating of the index structures. That is, -you can add, modify, or remove records from databases managed by Zebra -without rebuilding the entire index. Since this process involves -modifying structured files with various references between blocks of -data in the files, the update process is inherently sensitive to -system crashes, or to process interruptions: Anything but a -successfully completed update process will leave the register files in -an unknown state, and you will essentially have no recourse but to -re-index everything, or to restore the register files from a backup -medium. Further, while the update process is active, users cannot be -allowed to access the system, as the contents of the register files -may change unpredictably. - - - -You can solve these problems by enabling the shadow register system in -Zebra. During the updating procedure, zebraidx will temporarily -write changes to the involved files in a set of "shadow -files", without modifying the files that are accessed by the -active server processes. If the update procedure is interrupted by a -system crash or a signal, you simply repeat the procedure - the -register files have not been changed or damaged, and the partially -written shadow files are automatically deleted before the new updating -procedure commences. - - - -At the end of the updating procedure (or in a separate operation, if -you so desire), the system enters a "commit mode". First, -any active server processes are forced to access those blocks that -have been changed from the shadow files rather than from the main -register files; the unmodified blocks are still accessed at their -normal location (the shadow files are not a complete copy of the -register files - they only contain those parts that have actually been -modified). If the commit process is interrupted at any point during the -commit process, the server processes will continue to access the -shadow files until you can repeat the commit procedure and complete -the writing of data to the main register files. You can perform -multiple update operations to the registers before you commit the -changes to the system files, or you can execute the commit operation -at the end of each update operation. When the commit phase has -completed successfully, any running server processes are instructed to -switch their operations to the new, operational register, and the -temporary shadow files are deleted. - - - - - -How to Use Shadow Register Files - - -The first step is to allocate space on your system for the shadow -files. You do this by adding a shadow entry to the zebra.cfg -file. The syntax of the shadow entry is exactly the same as for -the register entry (see section ). The location of the shadow area should be -different from the location of the main register area (if you -have specified one - remember that if you provide no register -setting, the default register area is the -working directory of the server and indexing processes). - - - -The following excerpt from a zebra.cfg file shows one example of -a setup that configures both the main register location and the shadow -file area. Note that two directories or partitions have been set aside -for the shadow file area. You can specify any number of directories -for each of the file areas, but remember that there should be no -overlaps between the directories used for the main registers and the -shadow files, respectively. - - - - - -register: /d1:500M - -shadow: /scratch1:100M /scratch2:200M - - - - - -When shadow files are enabled, an extra command is available at the -zebraidx command line. In order to make changes to the system -take effect for the users, you'll have to submit a -"commit" command after a (sequence of) update -operation(s). You can ask the indexer to commit the changes -immediately after the update operation: - - - - - -$ zebraidx update /d1/records update /d2/more-records commit - - - - - -Or you can execute multiple updates before committing the changes: - - - - - -$ zebraidx -g books update /d1/records update /d2/more-records -$ zebraidx -g fun update /d3/fun-records -$ zebraidx commit - - - - - -If one of the update operations above had been interrupted, the commit -operation on the last line would fail: zebraidx will not let you -commit changes that would destroy the running register. You'll have to -rerun all of the update operations since your last commit operation, -before you can commit the new changes. - - - -Similarly, if the commit operation fails, zebraidx will not let -you start a new update operation before you have successfully repeated -the commit operation. The server processes will keep accessing the -shadow files rather than the (possibly damaged) blocks of the main -register files until the commit operation has successfully completed. - - - -You should be aware that update operations may take slightly longer -when the shadow register system is enabled, since more file access -operations are involved. Further, while the disk space required for -the shadow register data is modest for a small update operation, you -may prefer to disable the system if you are adding a very large number -of records to an already very large database (we use the terms -large and modest very loosely here, since every -application will have a different perception of size). To update the system -without the use of the the shadow files, simply run zebraidx with -the -n option (note that you do not have to execute the -commit command of zebraidx when you temporarily disable the -use of the shadow registers in this fashion. Note also that, just as -when the shadow registers are not enabled, server processes will be -barred from accessing the main register while the update procedure -takes place. - - - - - - - - - -Running the Maintenance Interface (zebraidx) - - -The following is a complete reference to the command line interface to -the zebraidx application. - - - -Syntax - - -$ zebraidx [options] command [directory] ... - - -Options - - - --t type - - -Update all files as type. Currently, the -types supported are text and grs.subtype. If no -subtype is provided for the GRS (General Record Structure) type, -the canonical input format is assumed (see section ). Generally, it -is probably advisable to specify the record types in the -zebra.cfg file -(see section ), to avoid -confusion at subsequent updates. - - - - --c config-file - - -Read the configuration file -config-file instead of zebra.cfg. - - - - --g group - - -Update the files according to the group -settings for group (see section -). - - - - --d database - - -The records located should be associated -with the database name database for access through the Z39.50 -server. - - - - --m mbytes - - -Use mbytes of megabytes before flushing -keys to background storage. This setting affects performance when -updating large databases. - - - - --n - - -Disable the use of shadow registers for this operation -(see section ). - - - - --s - - -Show analysis of the indexing process. The maintenance -program works in a read-only mode and doesn't change the state -of the index. This options is very useful when you wish to test a -new profile. - - - - --V - - -Show Zebra version. - - - - --v level - - -Set the log level to level. level -should be one of none, debug, and all. - - - - - - - -Commands - - - -Update directory - - -Update the register with the files -contained in directory. If no directory is provided, a list of -files is read from stdin. -See section . - - - - -Delete directory - - -Remove the records corresponding to -the files found under directory from the register. - - - - -Commit - - -Write the changes resulting from the last update -commands to the register. This command is only available if the use of -shadow register files is enabled (see section -). - - - - - - - - - -The Z39.50 Server - - -Running the Z39.50 Server (zebrasrv) - - -Syntax - - -zebrasrv [options] [listener-address ...] - - - - - -Options - - - --a APDU file - - -Specify a file for dumping PDUs (for diagnostic purposes). -The special name "-" sends output to stderr. - - - - --c config-file - - -Read configuration information from config-file. The default configuration is ./zebra.cfg. - - - - --S - - -Don't fork on connection requests. This can be useful for -symbolic-level debugging. The server can only accept a single -connection in this mode. - - - - --s - - -Use the SR protocol. - - - - --z - - -Use the Z39.50 protocol (default). These two options complement -eachother. You can use both multiple times on the same command -line, between listener-specifications (see below). This way, you -can set up the server to listen for connections in both protocols -concurrently, on different local ports. - - - - --l logfile - - -Specify an output file for the diagnostic -messages. The default is to write this information to stderr. - - - - --v log-level - - -The log level. Use a comma-separated list of members of the set -{fatal,debug,warn,log,all,none}. - - - - --u username - - -Set user ID. Sets the real UID of the server process to that of the -given username. It's useful if you aren't comfortable with having the -server run as root, but you need to start it as such to bind a -privileged port. - - - - --w working-directory - - -Change working directory. - - - - --i - - -Run under the Internet superserver, inetd. Make -sure you use the logfile option -l in conjunction with this -mode and specify the -l option before any other options. - - - - --t timeout - - -Set the idle session timeout (default 60 minutes). - - - - --k kilobytes - - -Set the (approximate) maximum size of -present response messages. Default is 1024 Kb (1 Mb). - - - - - - - -A listener-address consists of a transport mode followed by a -colon (:) followed by a listener address. The transport mode is -either osi or tcp. - - - -For TCP, an address has the form - - - - - -hostname | IP-number [: portnumber] - - - - - -The port number defaults to 210 (standard Z39.50 port). - - - -For OSI (only available if the server is compiled with XTI/mOSI -support enabled), the address form is - - - - - -[t-selector /] hostname | IP-number [: portnumber] - - - - - -The transport selector is given as a string of hex digits (with an even -number of digits). The default port number is 102 (RFC1006 port). - - - -Examples - - - - - -tcp:dranet.dra.com - -osi:0402/dbserver.osiworld.com:3000 - - - - - -In both cases, the special hostname "@" is mapped to -the address INADDR_ANY, which causes the server to listen on any local -interface. To start the server listening on the registered ports for -Z39.50 and SR over OSI/RFC1006, and to drop root privileges once the -ports are bound, execute the server like this (from a root shell): - - - - - -zebrasrv -u daemon tcp:@ -s osi:@ - - - - - -You can replace daemon with another user, eg. your own account, or -a dedicated IR server account. - - - -The default behavior for zebrasrv is to establish a single TCP/IP -listener, for the Z39.50 protocol, on port 9999. - - - - - -Z39.50 Protocol Support and Behavior - - -Initialization - - -During initialization, the server will negotiate to version 3 of the -Z39.50 protocol, and the option bits for Search, Present, Scan, -NamedResultSets, and concurrentOperations will be set, if requested by -the client. The maximum PDU size is negotiated down to a maximum of -1Mb by default. - - - - - -Search - - -The supported query type are 1 and 101. All operators are currently -supported with the restriction that only proximity units of type "word" are -supported for the proximity operator. -Queries can be arbitrarily complex. -Named result sets are supported, and result sets can be used as operands -without limitations. -Searches may span multiple databases. - - - -The server has full support for piggy-backed present requests (see -also the following section). - - - -Use attributes are interpreted according to the attribute sets which -have been loaded in the zebra.cfg file, and are matched against -specific fields as specified in the .abs file which describes the -profile of the records which have been loaded. If no Use -attribute is provided, a default of Bib-1 Any is assumed. - - - -If a Structure attribute of Phrase is used in conjunction with a -Completeness attribute of Complete (Sub)field, the term is -matched against the contents of the phrase (long word) register, if one -exists for the given Use attribute. -A phrase register is created for those fields in the .abs -file that contains a p-specifier. - - - -If Structure=Phrase is used in conjunction with -Incomplete Field - the default value for Completeness, the -search is directed against the normal word registers, but if the term -contains multiple words, the term will only match if all of the words -are found immediately adjacent, and in the given order. -The word search is performed on those fields that are indexed as -type w in the .abs file. - - - -If the Structure attribute is Word List, -Free-form Text, or Document Text, the term is treated as a -natural-language, relevance-ranked query. -This search type uses the word register, i.e. those fields -that are indexed as type w in the .abs file. - - - -If the Structure attribute is Numeric String the -term is treated as an integer. The search is performed on those -fields that are indexed as type n in the .abs file. - - - -If the Structure attribute is URx the -term is treated as a URX (URL) entity. The search is performed on those -fields that are indexed as type u in the .abs file. - - - -If the Structure attribute is Local Number the -term is treated as native Zebra Record Identifier. - - - -If the Relation attribute is Equals (default), the term is -matched in a normal fashion (modulo truncation and processing of -individual words, if required). If Relation is Less Than, -Less Than or Equal, Greater than, or Greater than or -Equal, the term is assumed to be numerical, and a standard regular -expression is constructed to match the given expression. If -Relation is Relevance, the standard natural-language query -processor is invoked. - - - -For the Truncation attribute, No Truncation is the default. -Left Truncation is not supported. Process # is supported, as -is Regxp-1. Regxp-2 enables the fault-tolerant (fuzzy) -search. As a default, a single error (deletion, insertion, -replacement) is accepted when terms are matched against the register -contents. - - - -Regular expressions - - -Each term in a query is interpreted as a regular expression if -the truncation value is either Regxp-1 (102) or Regxp-2 (103). -Both query types follow the same syntax with the operands: - - - -x - - -Matches the character x. - - - - -. - - -Matches any character. - - - - -[..] - - -Matches the set of characters specified; -such as [abc] or [a-c]. - - - - -and the operators: - - - -x* - - -Matches x zero or more times. Priority: high. - - - - -x+ - - -Matches x one or more times. Priority: high. - - - - -x? - - -Matches x once or twice. Priority: high. - - - - -xy - - -Matches x, then y. Priority: medium. - - - - -x|y - - -Matches either x or y. Priority: low. - - - - -The order of evaluation may be changed by using parentheses. - - - -If the first character of the Regxp-2 query is a plus character -(+) it marks the beginning of a section with non-standard -specifiers. The next plus character marks the end of the section. -Currently Zebra only supports one specifier, the error tolerance, -which consists one digit. - - - -Since the plus operator is normally a suffix operator the addition to -the query syntax doesn't violate the syntax for standard regular -expressions. - - - - - -Query examples - - -Phrase search for information retrieval in the title-register: - - - @attr 1=4 "information retrieval" - - - - - -Ranked search for the same thing: - - - @attr 1=4 @attr 2=102 "Information retrieval" - - - - - -Phrase search with a regular expression: - - - @attr 1=4 @attr 5=102 "informat.* retrieval" - - - - - -Ranked search with a regular expression: - - - @attr 1=4 @attr 5=102 @attr 2=102 "informat.* retrieval" - - - - - -In the GILS schema (gils.abs), the west-bounding-coordinate is -indexed as type n, and is therefore searched by specifying -structure=Numeric String. -To match all those records with west-bounding-coordinate greater -than -114 we use the following query: - - - @attr 4=109 @attr 2=5 @attr gils 1=2038 -114 - - - - - - - - - -Present - - -The present facility is supported in a standard fashion. The requested -record syntax is matched against the ones supported by the profile of -each record retrieved. If no record syntax is given, SUTRS is the -default. The requested element set name, again, is matched against any -provided by the relevant record profiles. - - - - - -Scan - - -The attribute combinations provided with the termListAndStartPoint are -processed in the same way as operands in a query (see above). -Currently, only the term and the globalOccurrences are returned with -the termInfo structure. - - - - - -Sort - - -Z39.50 specifies three diffent types of sort criterias. -Of these Zebra supports the attribute specification type in which -case the use attribute specifies the "Sort register". -Sort registers are created for those fields that are of type "sort" in -the default.idx file. -The corresponding character mapping file in default.idx specifies the -ordinal of each character used in the actual sort. - - - -Z39.50 allows the client to specify sorting on one or more input -result sets and one output result set. -Zebra supports sorting on one result set only which may or may not -be the same as the output result set. - - - - - -Close - - -If a Close PDU is received, the server will respond with a Close PDU -with reason=FINISHED, no matter which protocol version was negotiated -during initialization. If the protocol version is 3 or more, the -server will generate a Close PDU under certain circumstances, -including a session timeout (60 minutes by default), and certain kinds of -protocol errors. Once a Close PDU has been sent, the protocol -association is considered broken, and the transport connection will be -closed immediately upon receipt of further data, or following a short -timeout. - - - - - - - - - -The Record Model - - -The Zebra system is designed to support a wide range of data management -applications. The system can be configured to handle virtually any -kind of structured data. Each record in the system is associated with -a record schema which lends context to the data elements of the -record. Any number of record schema can coexist in the system. -Although it may be wise to use only a single schema within -one database, the system poses no such restrictions. - - - -The record model described in this chapter applies to the fundamental, -structured -record type grs as introduced in -section . - - - -Records pass through three different states during processing in the -system. - - - - - - - - -When records are accessed by the system, they are represented -in their local, or native format. This might be SGML or HTML files, -News or Mail archives, MARC records. If the system doesn't already -know how to read the type of data you need to store, you can set up an -input filter by preparing conversion rules based on regular -expressions and possibly augmented by a flexible scripting language (Tcl). The input filter -produces as output an internal representation: - - - - - - -When records are processed by the system, they are represented -in a tree-structure, constructed by tagged data elements hanging off a -root node. The tagged elements may contain data or yet more tagged -elements in a recursive structure. The system performs various -actions on this tree structure (indexing, element selection, schema -mapping, etc.), - - - - - - -Before transmitting records to the client, they are first -converted from the internal structure to a form suitable for exchange -over the network - according to the Z39.50 standard. - - - - - - - - -Local Representation - - -As mentioned earlier, Zebra places few restrictions on the type of -data that you can index and manage. Generally, whatever the form of -the data, it is parsed by an input filter specific to that format, and -turned into an internal structure that Zebra knows how to handle. This -process takes place whenever the record is accessed - for indexing and -retrieval. - - - -The RecordType parameter in the zebra.cfg file, or the -t -option to the indexer tells Zebra how to process input records. Two -basic types of processing are available - raw text and structured -data. Raw text is just that, and it is selected by providing the -argument text to Zebra. Structured records are all handled -internally using the basic mechanisms described in the subsequent -sections. Zebra can read structured records in many different formats. -How this is done is governed by additional parameters after the -"grs" keyboard, separated by "." characters. - - - -Three basic subtypes to the grs type are currently available: - - - - - - -grs.sgml - - -This is the canonical input format — -described below. It is a simple SGML-like syntax. - - - - -grs.regx.filter - - -This enables a user-supplied input -filter. The mechanisms of these filters are described below. - - - - -grs.marc.abstract syntax - - -This allows Zebra to read -records in the ISO2709 (MARC) encoding standard. In this case, the -last paramemeter abstract syntax names the .abs file (see below) -which describes the specific MARC structure of the input record as -well as the indexing rules. - - - - - - - -Canonical Input Format - - -Although input data can take any form, it is sometimes useful to -describe the record processing capabilities of the system in terms of -a single, canonical input format that gives access to the full -spectrum of structure and flexibility in the system. In Zebra, this -canonical format is an "SGML-like" syntax. - - - -To use the canonical format specify grs.sgml as the record -type, - - - -Consider a record describing an information resource (such a record is -sometimes known as a locator record). It might contain a field -describing the distributor of the information resource, which might in -turn be partitioned into various fields providing details about the -distributor, like this: - - - - - -<Distributor> - <Name> USGS/WRD </Name> - <Organization> USGS/WRD </Organization> - <Street-Address> - U.S. GEOLOGICAL SURVEY, 505 MARQUETTE, NW - </Street-Address> - <City> ALBUQUERQUE </City> - <State> NM </State> - <Zip-Code> 87102 </Zip-Code> - <Country> USA </Country> - <Telephone> (505) 766-5560 </Telephone> -</Distributor> - - - - - -NOTE: The indentation used above is used to illustrate how Zebra -interprets the markup. The indentation, in itself, has no -significance to the parser for the canonical input format, which -discards superfluous whitespace. - - - -The keywords surrounded by <...> are tags, while the -sections of text in between are the data elements. A data element -is characterized by its location in the tree that is made up by the -nested elements. Each element is terminated by a closing tag - -beginning with </, and containing the same symbolic tag-name as -the corresponding opening tag. The general closing tag - <>/ - -terminates the element started by the last opening tag. The -structuring of elements is significant. The element Telephone, -for instance, may be indexed and presented to the client differently, -depending on whether it appears inside the Distributor element, -or some other, structured data element such a Supplier element. - - - -Record Root - - -The first tag in a record describes the root node of the tree that -makes up the total record. In the canonical input format, the root tag -should contain the name of the schema that lends context to the -elements of the record (see section -). -The following is a GILS record that -contains only a single element (strictly speaking, that makes it an -illegal GILS record, since the GILS profile includes several mandatory -elements - Zebra does not validate the contents of a record against -the Z39.50 profile, however - it merely attempts to match up elements -of a local representation with the given schema): - - - - - -<gils> - <title>Zen and the Art of Motorcycle Maintenance</title> -</gils> - - - - - - - -Variants - - -Zebra allows you to provide individual data elements in a number of -variant forms. Examples of variant forms are textual data -elements which might appear in different languages, and images which -may appear in different formats or layouts. The variant system in -Zebra is -essentially a representation of the variant mechanism of -Z39.50-1995. - - - -The following is an example of a title element which occurs in two -different languages. - - - - - -<title> - <var lang lang "eng"> - Zen and the Art of Motorcycle Maintenance</> - <var lang lang "dan"> - Zen og Kunsten at Vedligeholde en Motorcykel</> -</title> - - - - - -The syntax of the variant element is <var class -type value>. The available values for the class and -type fields are given by the variant set that is associated with the -current schema (see section ). - - - -Variant elements are terminated by the general end-tag </>, by -the variant end-tag </var>, by the appearance of another variant -tag with the same class and value settings, or by the -appearance of another, normal tag. In other words, the end-tags for -the variants used in the example above could have been saved. - - - -Variant elements can be nested. The element - - - - - -<title> - <var lang lang "eng"><var body iana "text/plain"> - Zen and the Art of Motorcycle Maintenance -</title> - - - - - -Associates two variant components to the variant list for the title -element. - - - -Given the nesting rules described above, we could write - - - - - -<title> - <var body iana "text/plain> - <var lang lang "eng"> - Zen and the Art of Motorcycle Maintenance - <var lang lang "dan"> - Zen og Kunsten at Vedligeholde en Motorcykel -</title> - - - - - -The title element above comes in two variants. Both have the IANA body -type "text/plain", but one is in English, and the other in -Danish. The client, using the element selection mechanism of Z39.50, -can retrieve information about the available variant forms of data -elements, or it can select specific variants based on the requirements -of the end-user. - - - - - - - -Input Filters - - -In order to handle general input formats, Zebra allows the -operator to define filters which read individual records in their native format -and produce an internal representation that the system can -work with. - - - -Input filters are ASCII files, generally with the suffix .flt. -The system looks for the files in the directories given in the -profilePath setting in the zebra.cfg files. The record type -for the filter is grs.regx.filter-filename -(fundamental type grs, file read type regx, argument -filter-filename). - - - -Generally, an input filter consists of a sequence of rules, where each -rule consists of a sequence of expressions, followed by an action. The -expressions are evaluated against the contents of the input record, -and the actions normally contribute to the generation of an internal -representation of the record. - - - -An expression can be either of the following: - - - - - - -INIT - - -The action associated with this expression is evaluated -exactly once in the lifetime of the application, before any records -are read. It can be used in conjunction with an action that -initializes tables or other resources that are used in the processing -of input records. - - - - -BEGIN - - -Matches the beginning of the record. It can be used to -initialize variables, etc. Typically, the BEGIN rule is also used -to establish the root node of the record. - - - - -END - - -Matches the end of the record - when all of the contents -of the record has been processed. - - - - -/pattern/ - - -Matches a string of characters from the input -record. - - - - -BODY - - -This keyword may only be used between two patterns. It -matches everything between (not including) those patterns. - - - - -FINISH - - -The expression asssociated with this pattern is evaluated -once, before the application terminates. It can be used to release -system resources - typically ones allocated in the INIT step. - - - - - - - -An action is surrounded by curly braces ({...}), and consists of a -sequence of statements. Statements may be separated by newlines or -semicolons (;). Within actions, the strings that matched the -expressions immediately preceding the action can be referred to as -$0, $1, $2, etc. - - - -The available statements are: - - - - - - -begin type [parameter ... ] - - -Begin a new -data element. The type is one of the following: - - - -record - - -Begin a new record. The followingparameter should be the -name of the schema that describes the structure of the record, eg. -gils or wais (see below). The begin record call should -precede -any other use of the begin statement. - - - - -element - - -Begin a new tagged element. The parameter is the -name of the tag. If the tag is not matched anywhere in the tagsets -referenced by the current schema, it is treated as a local string -tag. - - - - -variant - - -Begin a new node in a variant tree. The parameters are -class type value. - - - - - - - - -data - - -Create a data element. The concatenated arguments make -up the value of the data element. The option -text signals that -the layout (whitespace) of the data should be retained for -transmission. The option -element tag wraps the data up in -the tag. The use of the -element option is equivalent to -preceding the command with a begin element command, and following -it with the end command. - - - - -end [type] - - -Close a tagged element. If no parameter is given, -the last element on the stack is terminated. The first parameter, if -any, is a type name, similar to the begin statement. For the -element type, a tag name can be provided to terminate a specific tag. - - - - - - - -The following input filter reads a Usenet news file, producing a -record in the WAIS schema. Note that the body of a news posting is -separated from the list of headers by a blank line (or rather a -sequence of two newline characters. - - - - - -BEGIN { begin record wais } - -/^From:/ BODY /$/ { data -element name $1 } -/^Subject:/ BODY /$/ { data -element title $1 } -/^Date:/ BODY /$/ { data -element lastModified $1 } -/\n\n/ BODY END { - begin element bodyOfDisplay - begin variant body iana "text/plain" - data -text $1 - end record - } - - - - - -If Zebra is compiled with support for Tcl (Tool Command Language) -enabled, the statements described above are supplemented with a complete -scripting environment, including control structures (conditional -expressions and loop constructs), and powerful string manipulation -mechanisms for modifying the elements of a record. Tcl is a popular -scripting environment, with several tutorials available both online -and in hardcopy. - - - -NOTE: Tcl support is not currently available, but will be -included with one of the next alpha or beta releases. - - - -NOTE: Variant support is not currently available in the input -filter, but will be included with one of the next alpha or beta -releases. - - - - - - - -Internal Representation - - -When records are manipulated by the system, they're represented in a -tree-structure, with data elements at the leaf nodes, and tags or -variant components at the non-leaf nodes. The root-node identifies the -schema that lends context to the tagging and structuring of the -record. Imagine a simple record, consisting of a 'title' element and -an 'author' element: - - - - - - TITLE "Zen and the Art of Motorcycle Maintenance" -ROOT - AUTHOR "Robert Pirsig" - - - - - -A slightly more complex record would have the author element consist -of two elements, a surname and a first name: - - - - - - TITLE "Zen and the Art of Motorcycle Maintenance" -ROOT - FIRST-NAME "Robert" - AUTHOR - SURNAME "Pirsig" - - - - - -The root of the record will refer to the record schema that describes -the structuring of this particular record. The schema defines the -element tags (TITLE, FIRST-NAME, etc.) that may occur in the record, as -well as the structuring (SURNAME should appear below AUTHOR, etc.). In -addition, the schema establishes element set names that are used by -the client to request a subset of the elements of a given record. The -schema may also establish rules for converting the record to a -different schema, by stating, for each element, a mapping to a -different tag path. - - - -Tagged Elements - - -A data element is characterized by its tag, and its position in the -structure of the record. For instance, while the tag "telephone -number" may be used different places in a record, we may need to -distinguish between these occurrences, both for searching and -presentation purposes. For instance, while the phone numbers for the -"customer" and the "service provider" are both -representatives for the same type of resource (a telephone number), it -is essential that they be kept separate. The record schema provides -the structure of the record, and names each data element (defined by -the sequence of tags - the tag path - by which the element can be -reached from the root of the record). - - - - - -Variants - - -The children of a tag node may be either more tag nodes, a data node -(possibly accompanied by tag nodes), -or a tree of variant nodes. The children of variant nodes are either -more variant nodes or a data node (possibly accompanied by more -variant nodes). Each leaf node, which is normally a -data node, corresponds to a variant form of the tagged element -identified by the tag which parents the variant tree. The following -title element occurs in two different languages: - - - - - - VARIANT LANG=ENG "War and Peace" -TITLE - VARIANT LANG=DAN "Krig og Fred" - - - - - -Which of the two elements are transmitted to the client by the server -depends on the specifications provided by the client, if any. - - - -In practice, each variant node is associated with a triple of class, -type, value, corresponding to the variant mechanism of Z39.50. - - - - - -Data Elements - - -Data nodes have no children (they are always leaf nodes in the record -tree). - - - -NOTE: Documentation needs extension here about types of nodes - numerical, -textual, etc., plus the various types of inclusion notes. - - - - - - - -Configuring Your Data Model - - -The following sections describe the configuration files that govern -the internal management of data records. The system searches for the files -in the directories specified by the profilePath setting in the -zebra.cfg file. - - - -The Abstract Syntax - - -The abstract syntax definition (also known as an Abstract Record -Structure, or ARS) is the focal point of the -record schema description. For a given schema, the ABS file may state any -or all of the following: - - - - - - - - -The object identifier of the Z39.50 schema associated -with the ARS, so that it can be referred to by the client. - - - - - - -The attribute set (which can possibly be a compound of multiple -sets) which applies in the profile. This is used when indexing and -searching the records belonging to the given profile. - - - - - - -The Tag set (again, this can consist of several different sets). -This is used when reading the records from a file, to recognize the -different tags, and when transmitting the record to the client - -mapping the tags to their numerical representation, if they are -known. - - - - - - -The variant set which is used in the profile. This provides a -vocabulary for specifying the forms of data that appear inside -the records. - - - - - - -Element set names, which are a shorthand way for the client to -ask for a subset of the data elements contained in a record. Element -set names, in the retrieval module, are mapped to element -specifications, which contain information equivalent to the -Espec-1 syntax of Z39.50. - - - - - - -Map tables, which may specify mappings to other database -profiles, if desired. - - - - - - -Possibly, a set of rules describing the mapping of elements to a -MARC representation. - - - - - - -A list of element descriptions (this is the actual ARS of the -schema, in Z39.50 terms), which lists the ways in which the various -tags can be used and organized hierarchically. - - - - - - - - -Several of the entries above simply refer to other files, which -describe the given objects. - - - - - -The Configuration Files - - -This section describes the syntax and use of the various tables which -are used by the retrieval module. - - - -The number of different file types may appear daunting at first, but -each type corresponds fairly clearly to a single aspect of the Z39.50 -retrieval facilities. Further, the average database administrator, -who is simply reusing an existing profile for which tables already -exist, shouldn't have to worry too much about the contents of these tables. - - - -Generally, the files are simple ASCII files, which can be maintained -using any text editor. Blank lines, and lines beginning with a (#) are -ignored. Any characters on a line followed by a (#) are also ignored. -All other -lines contain directives, which provide some setting or value -to the system. Generally, settings are characterized by a single -keyword, identifying the setting, followed by a number of parameters. -Some settings are repeatable (r), while others may occur only once in a -file. Some settings are optional (o), whicle others again are -mandatory (m). - - - - - -The Abstract Syntax (.abs) Files - - -The name of this file type is slightly misleading in Z39.50 terms, -since, apart from the actual abstract syntax of the profile, it also -includes most of the other definitions that go into a database -profile. - - - -When a record in the canonical, SGML-like format is read from a file -or from the database, the first tag of the file should reference the -profile that governs the layout of the record. If the first tag of the -record is, say, <gils>, the system will look for the profile -definition in the file gils.abs. Profile definitions are cached, -so they only have to be read once during the lifespan of the current -process. - - - -When writing your own input filters, the record-begin command -introduces the profile, and should always be called first thing when -introducing a new record. - - - -The file may contain the following directives: - - - - - - -name symbolic-name - - -(m) This provides a shorthand name or -description for the profile. Mostly useful for diagnostic purposes. - - - - -reference OID-name - - -(m) The reference name of the OID for -the profile. The reference names can be found in the util -module of YAZ. - - - - -attset filename - - -(m) The attribute set that is used for -indexing and searching records belonging to this profile. - - - - -tagset filename - - -(o) The tag set (if any) that describe -that fields of the records. - - - - -varset filename - - -(o) The variant set used in the profile. - - - - -maptab filename - - -(o,r) This points to a -conversion table that might be used if the client asks for the record -in a different schema from the native one. - - - -marc filename - - -(o) Points to a file containing parameters -for representing the record contents in the ISO2709 syntax. Read the -description of the MARC representation facility below. - - - -esetname name filename - - -(o,r) Associates the -given element set name with an element selection file. If an (@) is -given in place of the filename, this corresponds to a null mapping for -the given element set name. - - - -any tags - - -(o) This directive specifies a list of -attributes which should be appended to the attribute list given for each -element. The effect is to make every single element in the abstract -syntax searchable by way of the given attributes. This directive -provides an efficient way of supporting free-text searching across all -elements. However, it does increase the size of the index -significantly. The attributes can be qualified with a structure, as in -the elm directive below. - - - -elm path name attributes - - -(o,r) Adds an element -to the abstract record syntax of the schema. The path follows the -syntax which is suggested by the Z39.50 document - that is, a sequence -of tags separated by slashes (/). Each tag is given as a -comma-separated pair of tag type and -value surrounded by parenthesis. -The name is the name of the element, and the attributes -specifies which attributes to use when indexing the element in a -comma-separated list. A ! in -place of the attribute name is equivalent to specifying an attribute -name identical to the element name. A - in place of the attribute name -specifies that no indexing is to take place for the given element. The -attributes can be qualified with field types to specify which -character set should govern the indexing procedure for that field. The -same data element may be indexed into several different fields, using -different character set definitions. See the section -. -The default field type is "w" for -word. - - - - - - -NOTE: The mechanism for controlling indexing is not adequate for -complex databases, and will probably be moved into a separate -configuration table eventually. - - - -The following is an excerpt from the abstract syntax file for the GILS -profile. - - - - - -name gils -reference GILS-schema -attset gils.att -tagset gils.tag -varset var1.var - -maptab gils-usmarc.map - -# Element set names - -esetname VARIANT gils-variant.est # for WAIS-compliance -esetname B gils-b.est -esetname G gils-g.est -esetname F @ - -elm (1,10) rank - -elm (1,12) url - -elm (1,14) localControlNumber Local-number -elm (1,16) dateOfLastModification Date/time-last-modified -elm (2,1) title w:!,p:! -elm (4,1) controlIdentifier Identifier-standard -elm (2,6) abstract Abstract -elm (4,51) purpose ! -elm (4,52) originator - -elm (4,53) accessConstraints ! -elm (4,54) useConstraints ! -elm (4,70) availability - -elm (4,70)/(4,90) distributor - -elm (4,70)/(4,90)/(2,7) distributorName ! -elm (4,70)/(4,90)/(2,10 distributorOrganization ! -elm (4,70)/(4,90)/(4,2) distributorStreetAddress ! -elm (4,70)/(4,90)/(4,3) distributorCity ! - - - - - - - -The Attribute Set (.att) Files - - -This file type describes the Use elements of an attribute set. -It contains the following directives. - - - - - - -name symbolic-name - - -(m) This provides a shorthand name or -description for the attribute set. Mostly useful for diagnostic purposes. - - - -reference OID-name - - -(m) The reference name of the OID for -the attribute set. The reference names can be found in the util -module of YAZ. - - - -ordinal integer - - -(m) This value will be used to represent the -attribute set in the index. Care should be taken that each attribute -set has a unique ordinal value. - - - -include filename - - -(o,r) This directive is used to -include another attribute set as a part of the current one. This is -used when a new attribute set is defined as an extension to another -set. For instance, many new attribute sets are defined as extensions -to the bib-1 set. This is an important feature of the retrieval -system of Z39.50, as it ensures the highest possible level of -interoperability, as those access points of your database which are -derived from the external set (say, bib-1) can be used even by clients -who are unaware of the new set. - - - -att att-value att-name [local-value] - - -(o,r) This -repeatable directive introduces a new attribute to the set. The -attribute value is stored in the index (unless a local-value is -given, in which case this is stored). The name is used to refer to the -attribute from the abstract syntax. - - - - - - -This is an excerpt from the GILS attribute set definition. Notice how -the file describing the bib-1 attribute set is referenced. - - - - - -name gils -reference GILS-attset -include bib1.att -ordinal 2 - -att 2001 distributorName -att 2002 indextermsControlled -att 2003 purpose -att 2004 accessConstraints -att 2005 useConstraints - - - - - - - -The Tag Set (.tag) Files - - -This file type defines the tagset of the profile, possibly by -referencing other tag sets (most tag sets, for instance, will include -tagsetG and tagsetM from the Z39.50 specification. The file may -contain the following directives. - - - - - - -name symbolic-name - - -(m) This provides a shorthand name or -description for the tag set. Mostly useful for diagnostic purposes. - - - -reference OID-name - - -(o) The reference name of the OID for -the tag set. The reference names can be found in the util -module of YAZ. The directive is optional, since not all tag sets -are registered outside of their schema. - - - -type integer - - -(m) The type number of the tagset within the schema -profile (note: this specification really should belong to the .abs -file. This will be fixed in a future release). - - - -include filename - - -(o,r) This directive is used -to include the definitions of other tag sets into the current one. - - - -tag number names type - - -(o,r) Introduces a new -tag to the set. The number is the tag number as used in the protocol -(there is currently no mechanism for specifying string tags at this -point, but this would be quick work to add). The names parameter -is a list of names by which the tag should be recognized in the input -file format. The names should be separated by slashes (/). The -type is th recommended datatype of the tag. It should be one of -the following: - - - - - -structured - - - - - -string - - - - - -numeric - - - - - -bool - - - - - -oid - - - - - -generalizedtime - - - - - -intunit - - - - - -int - - - - - -octetstring - - - - - -null - - - - - - - - - - - -The following is an excerpt from the TagsetG definition file. - - - - - -name tagsetg -reference TagsetG -type 2 - -tag 1 title string -tag 2 author string -tag 3 publicationPlace string -tag 4 publicationDate string -tag 5 documentId string -tag 6 abstract string -tag 7 name string -tag 8 date generalizedtime -tag 9 bodyOfDisplay string -tag 10 organization string - - - - - - - -The Variant Set (.var) Files - - -The variant set file is a straightforward representation of the -variant set definitions associated with the protocol. At present, only -the Variant-1 set is known. - - - -These are the directives allowed in the file. - - - - - - -name symbolic-name - - -(m) This provides a shorthand name or -description for the variant set. Mostly useful for diagnostic purposes. - - - -reference OID-name - - -(o) The reference name of the OID for -the variant set, if one is required. The reference names can be found -in the util module of YAZ. - - - -class integer class-name - - -(m,r) Introduces a new -class to the variant set. - - - -type integer type-name datatype - - -(m,r) Addes a -new type to the current class (the one introduced by the most recent -class directive). The type names belong to the same name space as -the one used in the tag set definition file. - - - - - - -The following is an excerpt from the file describing the variant set -Variant-1. - - - - - -name variant-1 -reference Variant-1 - -class 1 variantId - - type 1 variantId octetstring - -class 2 body - - type 1 iana string - type 2 z39.50 string - type 3 other string - - - - - - - -The Element Set (.est) Files - - -The element set specification files describe a selection of a subset -of the elements of a database record. The element selection mechanism -is equivalent to the one supplied by the Espec-1 syntax of the -Z39.50 specification. In fact, the internal representation of an -element set specification is identical to the Espec-1 structure, -and we'll refer you to the description of that structure for most of -the detailed semantics of the directives below. - - - -NOTE: Not all of the Espec-1 functionality has been implemented yet. -The fields that are mentioned below all work as expected, unless -otherwise is noted. - - - -The directives available in the element set file are as follows: - - - - - - -defaultVariantSetId OID-name - - -(o) If variants are used in -the following, this should provide the name of the variantset used -(it's not currently possible to specify a different set in the -individual variant request). In almost all cases (certainly all -profiles known to us), the name Variant-1 should be given here. - - - -defaultVariantRequest variant-request - - -(o) This directive -provides a default variant request for -use when the individual element requests (see below) do not contain a -variant request. Variant requests consist of a blank-separated list of -variant components. A variant compont is a comma-separated, -parenthesized triple of variant class, type, and value (the two former -values being represented as integers). The value can currently only be -entered as a string (this will change to depend on the definition of -the variant in question). The special value (@) is interpreted as a -null value, however. - - - -simpleElement path ['variant' variant-request] - - -(o,r) This corresponds to a simple element request in Espec-1. The -path consists of a sequence of tag-selectors, where each of these can -consist of either: - - - - - - - - -A simple tag, consisting of a comma-separated type-value pair in -parenthesis, possibly followed by a colon (:) followed by an -occurrences-specification (see below). The tag-value can be a number -or a string. If the first character is an apostrophe ('), this forces -the value to be interpreted as a string, even if it appears to be numerical. - - - - - - -A WildThing, represented as a question mark (?), possibly -followed by a colon (:) followed by an occurrences specification (see -below). - - - - - - -A WildPath, represented as an asterisk (*). Note that the last -element of the path should not be a wildPath (wildpaths don't work in -this version). - - - - - - - - -The occurrences-specification can be either the string all, the -string last, or an explicit value-range. The value-range is -represented as an integer (the starting point), possibly followed by a -plus (+) and a second integer (the number of elements, default being -one). - - - -The variant-request has the same syntax as the defaultVariantRequest -above. Note that it may sometimes be useful to give an empty variant -request, simply to disable the default for a specific set of fields -(we aren't certain if this is proper Espec-1, but it works in -this implementation). - - - - - - -The following is an example of an element specification belonging to -the GILS profile. - - - - - -simpleelement (1,10) -simpleelement (1,12) -simpleelement (2,1) -simpleelement (1,14) -simpleelement (4,1) -simpleelement (4,52) - - - - - - - -The Schema Mapping (.map) Files - - -Sometimes, the client might want to receive a database record in -a schema that differs from the native schema of the record. For -instance, a client might only know how to process WAIS records, while -the database record is represented in a more specific schema, such as -GILS. In this module, a mapping of data to one of the MARC formats is -also thought of as a schema mapping (mapping the elements of the -record into fields consistent with the given MARC specification, prior -to actually converting the data to the ISO2709). This use of the -object identifier for USMARC as a schema identifier represents an -overloading of the OID which might not be entirely proper. However, -it represents the dual role of schema and record syntax which -is assumed by the MARC family in Z39.50. - - - -NOTE: The schema-mapping functions are so far limited to a -straightforward mapping of elements. This should be extended with -mechanisms for conversions of the element contents, and conditional -mappings of elements based on the record contents. - - - -These are the directives of the schema mapping file format: - - - - - - -targetName name - - -(m) A symbolic name for the target schema -of the table. Useful mostly for diagnostic purposes. - - - -targetRef OID-name - - -(m) An OID name for the target schema. -This is used, for instance, by a server receiving a request to present -a record in a different schema from the native one. The name, again, -is found in the oid module of YAZ. - - - -map element-name target-path - - -(o,r) Adds -an element mapping rule to the table. - - - - - - - - -The MARC (ISO2709) Representation (.mar) Files - - -This file provides rules for representing a record in the ISO2709 -format. The rules pertain mostly to the values of the constant-length -header of the record. - - - -NOTE: This will be described better. We're in the process of -re-evaluating and most likely changing the way that MARC records are -handled by the system. - - - - - -Field Structure and Character Sets - - - -In order to provide a flexible approach to national character set -handling, Zebra allows the administrator to configure the set up the -system to handle any 8-bit character set — including sets that -require multi-octet diacritics or other multi-octet characters. The -definition of a character set includes a specification of the -permissible values, their sort order (this affects the display in the -SCAN function), and relationships between upper- and lowercase -characters. Finally, the definition includes the specification of -space characters for the set. - - - -The operator can define different character sets for different fields, -typical examples being standard text fields, numerical fields, and -special-purpose fields such as WWW-style linkages (URx). - - - -The field types, and hence character sets, are associated with data -elements by the .abs files (see above). The file default.idx -provides the association between field type codes (as used in the .abs -files) and the character map files (with the .chr suffix). The format -of the .idx file is as follows - - - - - - -index field type code - - -This directive introduces a new -search index code. The argument is a one-character code to be used in the -.abs files to select this particular index type. An index, roughly, -corresponds to a particular structure attribute during search. Refer -to section . - - - -sort field code type - - -This directive introduces a -sort index. The argument is a one-character code to be used in the -.abs fie to select this particular index type. The corresponding -use attribute must be used in the sort request to refer to this -particular sort index. The corresponding character map (see below) -is used in the sort process. - - - -completeness boolean - - -This directive enables or disables -complete field indexing. The value of the boolean should be 0 -(disable) or 1. If completeness is enabled, the index entry will -contain the complete contents of the field (up to a limit), with words -(non-space characters) separated by single space characters -(normalized to " " on display). When completeness is -disabled, each word is indexed as a separate entry. Complete subfield -indexing is most useful for fields which are typically browsed (eg. -titles, authors, or subjects), or instances where a match on a -complete subfield is essential (eg. exact title searching). For fields -where completeness is disabled, the search engine will interpret a -search containing space characters as a word proximity search. - - - -charmap filename - - -This is the filename of the character -map to be used for this index for field type. - - - - - - -The contents of the character map files are structured as follows: - - - - - - -lowercase value-set - - -This directive introduces the basic -value set of the field type. The format is an ordered list (without -spaces) of the characters which may occur in "words" of -the given type. The order of the entries in the list determines the -sort order of the index. In addition to single characters, the -following combinations are legal: - - - - - - - - -Backslashes may be used to introduce three-digit octal, or -two-digit hex representations of single characters (preceded by x). -In addition, the combinations -\\, \\r, \\n, \\t, \\s (space — remember that real space-characters -may ot occur in the value definition), and \\ are recognised, -with their usual interpretation. - - - - - - -Curly braces {} may be used to enclose ranges of single -characters (possibly using the escape convention described in the -preceding point), eg. {a-z} to entroduce the standard range of ASCII -characters. Note that the interpretation of such a range depends on -the concrete representation in your local, physical character set. - - - - - - -paranthesises () may be used to enclose multi-byte characters - -eg. diacritics or special national combinations (eg. Spanish -"ll"). When found in the input stream (or a search term), -these characters are viewed and sorted as a single character, with a -sorting value depending on the position of the group in the value -statement. - - - - - - - - -uppercase value-set - - -This directive introduces the -upper-case equivalencis to the value set (if any). The number and -order of the entries in the list should be the same as in the -lowercase directive. - - - -space value-set - - -This directive introduces the character -which separate words in the input stream. Depending on the -completeness mode of the field in question, these characters either -terminate an index entry, or delimit individual "words" in -the input stream. The order of the elements is not significant — -otherwise the representation is the same as for the upercase and -lowercase directives. - - - -map value-set target - - -This directive introduces a -mapping between each of the members of the value-set on the left to -the character on the right. The character on the right must occur in -the value set (the lowercase directive) of the character set, but -it may be a paranthesis-enclosed multi-octet character. This directive -may be used to map diacritics to their base characters, or to map -HTML-style character-representations to their natural form, etc. - - - - - - - - - - -Exchange Formats - - -Converting records from the internal structure to en exchange format -is largely an automatic process. Currently, the following exchange -formats are supported: - - - - - - - - -GRS-1. The internal representation is based on GRS-1, so the -conversion here is straightforward. The system will create -applied variant and supported variant lists as required, if a record -contains variant information. - - - - - - -SUTRS. Again, the mapping is fairly straighforward. Indentation -is used to show the hierarchical structure of the record. All -"GRS" type records support both the GRS-1 and SUTRS -representations. - - - - - - -ISO2709-based formats (USMARC, etc.). Only records with a -two-level structure (corresponding to fields and subfields) can be -directly mapped to ISO2709. For records with a different structuring -(eg., GILS), the representation in a structure like USMARC involves a -schema-mapping (see section ), to an -"implied" USMARC schema (implied, -because there is no formal schema which specifies the use of the -USMARC fields outside of ISO2709). The resultant, two-level record is -then mapped directly from the internal representation to ISO2709. See -the GILS schema definition files for a detailed example of this -approach. - - - - - - -Explain. This representation is only available for records -belonging to the Explain schema. - - - - - - -Summary. This ASN-1 based structure is only available for records -belonging to the Summary schema - or schema which provide a mapping -to this schema (see the description of the schema mapping facility -above). - - - - - - -SOIF. Support for this syntax is experimental, and is currently -keyed to a private Index Data OID (1.2.840.10003.5.1000.81.2). All -abstract syntaxes can be mapped to the SOIF format, although nested -elements are represented by concatenation of the tag names at each -level. - - - - - - - - - - - + + Administrating &zebra; + + + + Unlike many simpler retrieval systems, &zebra; supports safe, incremental + updates to an existing index. + + + + Normally, when &zebra; modifies the index it reads a number of records + that you specify. + Depending on your specifications and on the contents of each record + one the following events take place for each record: + + + + Insert + + + The record is indexed as if it never occurred before. + Either the &zebra; system doesn't know how to identify the record or + &zebra; can identify the record but didn't find it to be already indexed. + + + + + Modify + + + The record has already been indexed. + In this case either the contents of the record or the location + (file) of the record indicates that it has been indexed before. + + + + + Delete + + + The record is deleted from the index. As in the + update-case it must be able to identify the record. + + + + + + + + Please note that in both the modify- and delete- case the &zebra; + indexer must be able to generate a unique key that identifies the record + in question (more on this below). + + + + To administrate the &zebra; retrieval system, you run the + zebraidx program. + This program supports a number of options which are preceded by a dash, + and a few commands (not preceded by dash). + + + + Both the &zebra; administrative tool and the &acro.z3950; server share a + set of index files and a global configuration file. + The name of the configuration file defaults to + zebra.cfg. + The configuration file includes specifications on how to index + various kinds of records and where the other configuration files + are located. zebrasrv and zebraidx + must be run in the directory where the + configuration file lives unless you indicate the location of the + configuration file by option -c. + + + + Record Types + + + Indexing is a per-record process, in which either insert/modify/delete + will occur. Before a record is indexed search keys are extracted from + whatever might be the layout the original record (sgml,html,text, etc..). + The &zebra; system currently supports two fundamental types of records: + structured and simple text. + To specify a particular extraction process, use either the + command line option -t or specify a + recordType setting in the configuration file. + + + + + + The &zebra; Configuration File + + + The &zebra; configuration file, read by zebraidx and + zebrasrv defaults to zebra.cfg + unless specified by -c option. + + + + You can edit the configuration file with a normal text editor. + parameter names and values are separated by colons in the file. Lines + starting with a hash sign (#) are + treated as comments. + + + + If you manage different sets of records that share common + characteristics, you can organize the configuration settings for each + type into "groups". + When zebraidx is run and you wish to address a + given group you specify the group name with the -g + option. + In this case settings that have the group name as their prefix + will be used by zebraidx. + If no -g option is specified, the settings + without prefix are used. + + + + In the configuration file, the group name is placed before the option + name itself, separated by a dot (.). For instance, to set the record type + for group public to grs.sgml + (the &acro.sgml;-like format for structured records) you would write: + + + + + public.recordType: grs.sgml + + + + + To set the default value of the record type to text + write: + + + + + recordType: text + + + + + The available configuration settings are summarized below. They will be + explained further in the following sections. + + + + + + + + + + group + .recordType[.name]: + type + + + + Specifies how records with the file extension + name should be handled by the indexer. + This option may also be specified as a command line option + (-t). Note that if you do not specify a + name, the setting applies to all files. + In general, the record type specifier consists of the elements (each + element separated by dot), fundamental-type, + file-read-type and arguments. Currently, two + fundamental types exist, text and + grs. + + + + + group.recordId: + record-id-spec + + + Specifies how the records are to be identified when updated. See + . + + + + + group.database: + database + + + Specifies the &acro.z3950; database name. + + + + + + group.storeKeys: + boolean + + + Specifies whether key information should be saved for a given + group of records. If you plan to update/delete this type of + records later this should be specified as 1; otherwise it + should be 0 (default), to save register space. + + See . + + + + + group.storeData: + boolean + + + Specifies whether the records should be stored internally + in the &zebra; system files. + If you want to maintain the raw records yourself, + this option should be false (0). + If you want &zebra; to take care of the records for you, it + should be true(1). + + + + + + register: register-location + + + Specifies the location of the various register files that &zebra; uses + to represent your databases. + See . + + + + + shadow: register-location + + + Enables the safe update facility of &zebra;, and + tells the system where to place the required, temporary files. + See . + + + + + lockDir: directory + + + Directory in which various lock files are stored. + + + + + keyTmpDir: directory + + + Directory in which temporary files used during zebraidx's update + phase are stored. + + + + + setTmpDir: directory + + + Specifies the directory that the server uses for temporary result sets. + If not specified /tmp will be used. + + + + + profilePath: path + + + Specifies a path of profile specification files. + The path is composed of one or more directories separated by + colon. Similar to PATH for UNIX systems. + + + + + + modulePath: path + + + Specifies a path of record filter modules. + The path is composed of one or more directories separated by + colon. Similar to PATH for UNIX systems. + The 'make install' procedure typically puts modules in + /usr/local/lib/idzebra-2.0/modules. + + + + + + index: filename + + + Defines the filename which holds fields structure + definitions. If omitted, the file default.idx + is read. + Refer to for + more information. + + + + + + sortmax: integer + + + Specifies the maximum number of records that will be sorted + in a result set. If the result set contains more than + integer records, records after the + limit will not be sorted. If omitted, the default value is + 1,000. + + + + + + staticrank: integer + + + Enables whether static ranking is to be enabled (1) or + disabled (0). If omitted, it is disabled - corresponding + to a value of 0. + Refer to . + + + + + + + estimatehits: integer + + + Controls whether &zebra; should calculate approximate hit counts and + at which hit count it is to be enabled. + A value of 0 disables approximate hit counts. + For a positive value approximate hit count is enabled + if it is known to be larger than integer. + + + Approximate hit counts can also be triggered by a particular + attribute in a query. + Refer to . + + + + + + attset: filename + + + Specifies the filename(s) of attribute set files for use in + searching. In many configurations bib1.att + is used, but that is not required. If Classic Explain + attributes is to be used for searching, + explain.att must be given. + The path to att-files in general can be given using + profilePath setting. + See also . + + + + + memMax: size + + + Specifies size of internal memory + to use for the zebraidx program. + The amount is given in megabytes - default is 4 (4 MB). + The more memory, the faster large updates happen, up to about + half the free memory available on the computer. + + + + + tempfiles: Yes/Auto/No + + + Tells zebra if it should use temporary files when indexing. The + default is Auto, in which case zebra uses temporary files only + if it would need more that memMax + megabytes of memory. This should be good for most uses. + + + + + + root: dir + + + Specifies a directory base for &zebra;. All relative paths + given (in profilePath, register, shadow) are based on this + directory. This setting is useful if your &zebra; server + is running in a different directory from where + zebra.cfg is located. + + + + + + passwd: file + + + Specifies a file with description of user accounts for &zebra;. + The format is similar to that known to Apache's htpasswd files + and UNIX' passwd files. Non-empty lines not beginning with + # are considered account lines. There is one account per-line. + A line consists of fields separate by a single colon character. + First field is username, second is password. + + + + + + passwd.c: file + + + Specifies a file with description of user accounts for &zebra;. + File format is similar to that used by the passwd directive except + that the password are encrypted. Use Apache's htpasswd or similar + for maintenance. + + + + + + perm.user: + permstring + + + Specifies permissions (privilege) for a user that are allowed + to access &zebra; via the passwd system. There are two kinds + of permissions currently: read (r) and write(w). By default + users not listed in a permission directive are given the read + privilege. To specify permissions for a user with no + username, or &acro.z3950; anonymous style use + anonymous. The permstring consists of + a sequence of characters. Include character w + for write/update access, r for read access and + a to allow anonymous access through this account. + + + + + + dbaccess: accessfile + + + Names a file which lists database subscriptions for individual users. + The access file should consists of lines of the form + username: dbnames, where dbnames is a list of + database names, separated by '+'. No whitespace is allowed in the + database list. + + + + + + encoding: charsetname + + + Tells &zebra; to interpret the terms in Z39.50 queries as + having been encoded using the specified character + encoding. The default is ISO-8859-1; one + useful alternative is UTF-8. + + + + + + storeKeys: value + + + Specifies whether &zebra; keeps a copy of indexed keys. + Use a value of 1 to enable; 0 to disable. If storeKeys setting is + omitted, it is enabled. Enabled storeKeys + are required for updating and deleting records. Disable only + storeKeys to save space and only plan to index data once. + + + + + + storeData: value + + + Specifies whether &zebra; keeps a copy of indexed records. + Use a value of 1 to enable; 0 to disable. If storeData setting is + omitted, it is enabled. A storeData setting of 0 (disabled) makes + Zebra fetch records from the original locaction in the file + system using filename, file offset and file length. For the + DOM and ALVIS filter, the storeData setting is ignored. + + + + + + + + + + + Locating Records + + + The default behavior of the &zebra; system is to reference the + records from their original location, i.e. where they were found when you + run zebraidx. + That is, when a client wishes to retrieve a record + following a search operation, the files are accessed from the place + where you originally put them - if you remove the files (without + running zebraidx again, the server will return + diagnostic number 14 (``System error in presenting records'') to + the client. + + + + If your input files are not permanent - for example if you retrieve + your records from an outside source, or if they were temporarily + mounted on a CD-ROM drive, + you may want &zebra; to make an internal copy of them. To do this, + you specify 1 (true) in the storeData setting. When + the &acro.z3950; server retrieves the records they will be read from the + internal file structures of the system. + + + + + + Indexing with no Record IDs (Simple Indexing) + + + If you have a set of records that are not expected to change over time + you may can build your database without record IDs. + This indexing method uses less space than the other methods and + is simple to use. + + + + To use this method, you simply omit the recordId entry + for the group of files that you index. To add a set of records you use + zebraidx with the update command. The + update command will always add all of the records that it + encounters to the index - whether they have already been indexed or + not. If the set of indexed files change, you should delete all of the + index files, and build a new index from scratch. + + + + Consider a system in which you have a group of text files called + simple. + That group of records should belong to a &acro.z3950; database called + textbase. + The following zebra.cfg file will suffice: + + + + + profilePath: /usr/local/idzebra/tab + attset: bib1.att + simple.recordType: text + simple.database: textbase + + + + + + Since the existing records in an index can not be addressed by their + IDs, it is impossible to delete or modify records when using this method. + + + + + + Indexing with File Record IDs + + + If you have a set of files that regularly change over time: Old files + are deleted, new ones are added, or existing files are modified, you + can benefit from using the file ID + indexing methodology. + Examples of this type of database might include an index of WWW + resources, or a USENET news spool area. + Briefly speaking, the file key methodology uses the directory paths + of the individual records as a unique identifier for each record. + To perform indexing of a directory with file keys, again, you specify + the top-level directory after the update command. + The command will recursively traverse the directories and compare + each one with whatever have been indexed before in that same directory. + If a file is new (not in the previous version of the directory) it + is inserted into the registers; if a file was already indexed and + it has been modified since the last update, the index is also + modified; if a file has been removed since the last + visit, it is deleted from the index. + + + + The resulting system is easy to administrate. To delete a record you + simply have to delete the corresponding file (say, with the + rm command). And to add records you create new + files (or directories with files). For your changes to take effect + in the register you must run zebraidx update with + the same directory root again. This mode of operation requires more + disk space than simpler indexing methods, but it makes it easier for + you to keep the index in sync with a frequently changing set of data. + If you combine this system with the safe update + facility (see below), you never have to take your server off-line for + maintenance or register updating purposes. + + + + To enable indexing with pathname IDs, you must specify + file as the value of recordId + in the configuration file. In addition, you should set + storeKeys to 1, since the &zebra; + indexer must save additional information about the contents of each record + in order to modify the indexes correctly at a later time. + + + + + + For example, to update records of group esdd + located below + /data1/records/ you should type: + + $ zebraidx -g esdd update /data1/records + + + + + The corresponding configuration file includes: + + esdd.recordId: file + esdd.recordType: grs.sgml + esdd.storeKeys: 1 + + + + + You cannot start out with a group of records with simple + indexing (no record IDs as in the previous section) and then later + enable file record Ids. &zebra; must know from the first time that you + index the group that + the files should be indexed with file record IDs. + + + + + You cannot explicitly delete records when using this method (using the + delete command to zebraidx. Instead + you have to delete the files from the file system (or move them to a + different location) + and then run zebraidx with the + update command. + + + + + + Indexing with General Record IDs + + + When using this method you construct an (almost) arbitrary, internal + record key based on the contents of the record itself and other system + information. If you have a group of records that explicitly associates + an ID with each record, this method is convenient. For example, the + record format may contain a title or a ID-number - unique within the group. + In either case you specify the &acro.z3950; attribute set and use-attribute + location in which this information is stored, and the system looks at + that field to determine the identity of the record. + + + + As before, the record ID is defined by the recordId + setting in the configuration file. The value of the record ID specification + consists of one or more tokens separated by whitespace. The resulting + ID is represented in the index by concatenating the tokens and + separating them by ASCII value (1). + + + + There are three kinds of tokens: + + + + Internal record info + + + The token refers to a key that is + extracted from the record. The syntax of this token is + ( set , + use ), + where set is the + attribute set name use is the + name or value of the attribute. + + + + + System variable + + + The system variables are preceded by + + + $ + + and immediately followed by the system variable name, which + may one of + + + + group + + + Group name. + + + + + database + + + Current database specified. + + + + + type + + + Record type. + + + + + + + + + Constant string + + + A string used as part of the ID — surrounded + by single- or double quotes. + + + + + + + + For instance, the sample GILS records that come with the &zebra; + distribution contain a unique ID in the data tagged Control-Identifier. + The data is mapped to the &acro.bib1; use attribute Identifier-standard + (code 1007). To use this field as a record id, specify + (bib1,Identifier-standard) as the value of the + recordId in the configuration file. + If you have other record types that uses the same field for a + different purpose, you might add the record type + (or group or database name) to the record id of the gils + records as well, to prevent matches with other types of records. + In this case the recordId might be set like this: + + + gils.recordId: $type (bib1,Identifier-standard) + + + + + + (see + for details of how the mapping between elements of your records and + searchable attributes is established). + + + + As for the file record ID case described in the previous section, + updating your system is simply a matter of running + zebraidx + with the update command. However, the update with general + keys is considerably slower than with file record IDs, since all files + visited must be (re)read to discover their IDs. + + + + As you might expect, when using the general record IDs + method, you can only add or modify existing records with the + update command. + If you wish to delete records, you must use the, + delete command, with a directory as a parameter. + This will remove all records that match the files below that root + directory. + + + + + + Register Location + + + Normally, the index files that form dictionaries, inverted + files, record info, etc., are stored in the directory where you run + zebraidx. If you wish to store these, possibly large, + files somewhere else, you must add the register + entry to the zebra.cfg file. + Furthermore, the &zebra; system allows its file + structures to span multiple file systems, which is useful for + managing very large databases. + + + + The value of the register setting is a sequence + of tokens. Each token takes the form: + + dir:size + + The dir specifies a directory in which index files + will be stored and the size specifies the maximum + size of all files in that directory. The &zebra; indexer system fills + each directory in the order specified and use the next specified + directories as needed. + The size is an integer followed by a qualifier + code, + b for bytes, + k for kilobytes. + M for megabytes, + G for gigabytes. + Specifying a negative value disables the checking (it still needs the unit, + use -1b). + + + + For instance, if you have allocated three disks for your register, and + the first disk is mounted + on /d1 and has 2GB of free space, the + second, mounted on /d2 has 3.6 GB, and the third, + on which you have more space than you bother to worry about, mounted on + /d3 you could put this entry in your configuration file: + + + register: /d1:2G /d2:3600M /d3:-1b + + + + + Note that &zebra; does not verify that the amount of space specified is + actually available on the directory (file system) specified - it is + your responsibility to ensure that enough space is available, and that + other applications do not attempt to use the free space. In a large + production system, it is recommended that you allocate one or more + file system exclusively to the &zebra; register files. + + + + + + Safe Updating - Using Shadow Registers + + + Description + + + The &zebra; server supports updating of the index + structures. That is, you can add, modify, or remove records from + databases managed by &zebra; without rebuilding the entire index. + Since this process involves modifying structured files with various + references between blocks of data in the files, the update process + is inherently sensitive to system crashes, or to process interruptions: + Anything but a successfully completed update process will leave the + register files in an unknown state, and you will essentially have no + recourse but to re-index everything, or to restore the register files + from a backup medium. + Further, while the update process is active, users cannot be + allowed to access the system, as the contents of the register files + may change unpredictably. + + + + You can solve these problems by enabling the shadow register system in + &zebra;. + During the updating procedure, zebraidx will temporarily + write changes to the involved files in a set of "shadow + files", without modifying the files that are accessed by the + active server processes. If the update procedure is interrupted by a + system crash or a signal, you simply repeat the procedure - the + register files have not been changed or damaged, and the partially + written shadow files are automatically deleted before the new updating + procedure commences. + + + + At the end of the updating procedure (or in a separate operation, if + you so desire), the system enters a "commit mode". First, + any active server processes are forced to access those blocks that + have been changed from the shadow files rather than from the main + register files; the unmodified blocks are still accessed at their + normal location (the shadow files are not a complete copy of the + register files - they only contain those parts that have actually been + modified). If the commit process is interrupted at any point during the + commit process, the server processes will continue to access the + shadow files until you can repeat the commit procedure and complete + the writing of data to the main register files. You can perform + multiple update operations to the registers before you commit the + changes to the system files, or you can execute the commit operation + at the end of each update operation. When the commit phase has + completed successfully, any running server processes are instructed to + switch their operations to the new, operational register, and the + temporary shadow files are deleted. + + + + + + How to Use Shadow Register Files + + + The first step is to allocate space on your system for the shadow + files. + You do this by adding a shadow entry to the + zebra.cfg file. + The syntax of the shadow entry is exactly the + same as for the register entry + (see ). + The location of the shadow area should be + different from the location of the main register + area (if you have specified one - remember that if you provide no + register setting, the default register area is the + working directory of the server and indexing processes). + + + + The following excerpt from a zebra.cfg file shows + one example of a setup that configures both the main register + location and the shadow file area. + Note that two directories or partitions have been set aside + for the shadow file area. You can specify any number of directories + for each of the file areas, but remember that there should be no + overlaps between the directories used for the main registers and the + shadow files, respectively. + + + + + register: /d1:500M + shadow: /scratch1:100M /scratch2:200M + + + + + + When shadow files are enabled, an extra command is available at the + zebraidx command line. + In order to make changes to the system take effect for the + users, you'll have to submit a "commit" command after a + (sequence of) update operation(s). + + + + + + $ zebraidx update /d1/records + $ zebraidx commit + + + + + + Or you can execute multiple updates before committing the changes: + + + + + + $ zebraidx -g books update /d1/records /d2/more-records + $ zebraidx -g fun update /d3/fun-records + $ zebraidx commit + + + + + + If one of the update operations above had been interrupted, the commit + operation on the last line would fail: zebraidx + will not let you commit changes that would destroy the running register. + You'll have to rerun all of the update operations since your last + commit operation, before you can commit the new changes. + + + + Similarly, if the commit operation fails, zebraidx + will not let you start a new update operation before you have + successfully repeated the commit operation. + The server processes will keep accessing the shadow files rather + than the (possibly damaged) blocks of the main register files + until the commit operation has successfully completed. + + + + You should be aware that update operations may take slightly longer + when the shadow register system is enabled, since more file access + operations are involved. Further, while the disk space required for + the shadow register data is modest for a small update operation, you + may prefer to disable the system if you are adding a very large number + of records to an already very large database (we use the terms + large and modest + very loosely here, since every application will have a + different perception of size). + To update the system without the use of the the shadow files, + simply run zebraidx with the -n + option (note that you do not have to execute the + commit command of zebraidx + when you temporarily disable the use of the shadow registers in + this fashion. + Note also that, just as when the shadow registers are not enabled, + server processes will be barred from accessing the main register + while the update procedure takes place. + + + + + + + + + Relevance Ranking and Sorting of Result Sets + + + Overview + + The default ordering of a result set is left up to the server, + which inside &zebra; means sorting in ascending document ID order. + This is not always the order humans want to browse the sometimes + quite large hit sets. Ranking and sorting comes to the rescue. + + + + In cases where a good presentation ordering can be computed at + indexing time, we can use a fixed static ranking + scheme, which is provided for the alvis + indexing filter. This defines a fixed ordering of hit lists, + independently of the query issued. + + + + There are cases, however, where relevance of hit set documents is + highly dependent on the query processed. + Simply put, dynamic relevance ranking + sorts a set of retrieved records such that those most likely to be + relevant to your request are retrieved first. + Internally, &zebra; retrieves all documents that satisfy your + query, and re-orders the hit list to arrange them based on + a measurement of similarity between your query and the content of + each record. + + + + Finally, there are situations where hit sets of documents should be + sorted during query time according to the + lexicographical ordering of certain sort indexes created at + indexing time. + + + + + + Static Ranking + + + &zebra; uses internally inverted indexes to look up term frequencies + in documents. Multiple queries from different indexes can be + combined by the binary boolean operations AND, + OR and/or NOT (which + is in fact a binary AND NOT operation). + To ensure fast query execution + speed, all indexes have to be sorted in the same order. + + + The indexes are normally sorted according to document + ID in + ascending order, and any query which does not invoke a special + re-ranking function will therefore retrieve the result set in + document + ID + order. + + + If one defines the + + staticrank: 1 + + directive in the main core &zebra; configuration file, the internal document + keys used for ordering are augmented by a preceding integer, which + contains the static rank of a given document, and the index lists + are ordered + first by ascending static rank, + then by ascending document ID. + Zero + is the ``best'' rank, as it occurs at the + beginning of the list; higher numbers represent worse scores. + + + The experimental alvis filter provides a + directive to fetch static rank information out of the indexed &acro.xml; + records, thus making all hit sets ordered + after ascending static + rank, and for those doc's which have the same static rank, ordered + after ascending doc ID. + See for the gory details. + + + + + + Dynamic Ranking + + In order to fiddle with the static rank order, it is necessary to + invoke additional re-ranking/re-ordering using dynamic + ranking or score functions. These functions return positive + integer scores, where highest score is + ``best''; + hit sets are sorted according to descending + scores (in contrary + to the index lists which are sorted according to + ascending rank number and document ID). + + + Dynamic ranking is enabled by a directive like one of the + following in the zebra configuration file (use only one of these a time!): + + rank: rank-1 # default TDF-IDF like + rank: rank-static # dummy do-nothing + + + + + Dynamic ranking is done at query time rather than + indexing time (this is why we + call it ``dynamic ranking'' in the first place ...) + It is invoked by adding + the &acro.bib1; relation attribute with + value ``relevance'' to the &acro.pqf; query (that is, + @attr 2=102, see also + + The &acro.bib1; Attribute Set Semantics, also in + HTML). + To find all articles with the word Eoraptor in + the title, and present them relevance ranked, issue the &acro.pqf; query: + + @attr 2=102 @attr 1=4 Eoraptor + + + + + Dynamically ranking using &acro.pqf; queries with the 'rank-1' + algorithm + + + The default rank-1 ranking module implements a + TF/IDF (Term Frequecy over Inverse Document Frequency) like + algorithm. In contrast to the usual definition of TF/IDF + algorithms, which only considers searching in one full-text + index, this one works on multiple indexes at the same time. + More precisely, + &zebra; does boolean queries and searches in specific addressed + indexes (there are inverted indexes pointing from terms in the + dictionary to documents and term positions inside documents). + It works like this: + + + Query Components + + + First, the boolean query is dismantled into its principal components, + i.e. atomic queries where one term is looked up in one index. + For example, the query + + @attr 2=102 @and @attr 1=1010 Utah @attr 1=1018 Springer + + is a boolean AND between the atomic parts + + @attr 2=102 @attr 1=1010 Utah + + and + + @attr 2=102 @attr 1=1018 Springer + + which gets processed each for itself. + + + + + + Atomic hit lists + + + Second, for each atomic query, the hit list of documents is + computed. + + + In this example, two hit lists for each index + @attr 1=1010 and + @attr 1=1018 are computed. + + + + + + Atomic scores + + + Third, each document in the hit list is assigned a score (_if_ ranking + is enabled and requested in the query) using a TF/IDF scheme. + + + In this example, both atomic parts of the query assign the magic + @attr 2=102 relevance attribute, and are + to be used in the relevance ranking functions. + + + It is possible to apply dynamic ranking on only parts of the + &acro.pqf; query: + + @and @attr 2=102 @attr 1=1010 Utah @attr 1=1018 Springer + + searches for all documents which have the term 'Utah' on the + body of text, and which have the term 'Springer' in the publisher + field, and sort them in the order of the relevance ranking made on + the body-of-text index only. + + + + + + Hit list merging + + + Fourth, the atomic hit lists are merged according to the boolean + conditions to a final hit list of documents to be returned. + + + This step is always performed, independently of the fact that + dynamic ranking is enabled or not. + + + + + + Document score computation + + + Fifth, the total score of a document is computed as a linear + combination of the atomic scores of the atomic hit lists + + + Ranking weights may be used to pass a value to a ranking + algorithm, using the non-standard &acro.bib1; attribute type 9. + This allows one branch of a query to use one value while + another branch uses a different one. For example, we can search + for utah in the + @attr 1=4 index with weight 30, as + well as in the @attr 1=1010 index with weight 20: + + @attr 2=102 @or @attr 9=30 @attr 1=4 utah @attr 9=20 @attr 1=1010 city + + + + The default weight is + sqrt(1000) ~ 34 , as the &acro.z3950; standard prescribes that the top score + is 1000 and the bottom score is 0, encoded in integers. + + + + The ranking-weight feature is experimental. It may change in future + releases of zebra. + + + + + + + Re-sorting of hit list + + + Finally, the final hit list is re-ordered according to scores. + + + + + + + + + + The rank-1 algorithm + does not use the static rank + information in the list keys, and will produce the same ordering + with or without static ranking enabled. + + + + + + + + Dynamic ranking is not compatible + with estimated hit sizes, as all documents in + a hit set must be accessed to compute the correct placing in a + ranking sorted list. Therefore the use attribute setting + @attr 2=102 clashes with + @attr 9=integer. + + + + + + + + + Dynamically ranking &acro.cql; queries + + Dynamic ranking can be enabled during sever side &acro.cql; + query expansion by adding @attr 2=102 + chunks to the &acro.cql; config file. For example + + relationModifier.relevant = 2=102 + + invokes dynamic ranking each time a &acro.cql; query of the form + + Z> querytype cql + Z> f alvis.text =/relevant house + + is issued. Dynamic ranking can also be automatically used on + specific &acro.cql; indexes by (for example) setting + + index.alvis.text = 1=text 2=102 + + which then invokes dynamic ranking each time a &acro.cql; query of the form + + Z> querytype cql + Z> f alvis.text = house + + is issued. + + + + + + + + + Sorting + + &zebra; sorts efficiently using special sorting indexes + (type=s; so each sortable index must be known + at indexing time, specified in the configuration of record + indexing. For example, to enable sorting according to the &acro.bib1; + Date/time-added-to-db field, one could add the line + + xelm /*/@created Date/time-added-to-db:s + + to any .abs record-indexing configuration file. + Similarly, one could add an indexing element of the form + + + + ]]> + to any alvis-filter indexing stylesheet. + + + Indexing can be specified at searching time using a query term + carrying the non-standard + &acro.bib1; attribute-type 7. This removes the + need to send a &acro.z3950; Sort Request + separately, and can dramatically improve latency when the client + and server are on separate networks. + The sorting part of the query is separate from the rest of the + query - the actual search specification - and must be combined + with it using OR. + + + A sorting subquery needs two attributes: an index (such as a + &acro.bib1; type-1 attribute) specifying which index to sort on, and a + type-7 attribute whose value is be 1 for + ascending sorting, or 2 for descending. The + term associated with the sorting attribute is the priority of + the sort key, where 0 specifies the primary + sort key, 1 the secondary sort key, and so + on. + + For example, a search for water, sort by title (ascending), + is expressed by the &acro.pqf; query + + @or @attr 1=1016 water @attr 7=1 @attr 1=4 0 + + whereas a search for water, sort by title ascending, + then date descending would be + + @or @or @attr 1=1016 water @attr 7=1 @attr 1=4 0 @attr 7=2 @attr 1=30 1 + + + + Notice the fundamental differences between dynamic + ranking and sorting: there can be + only one ranking function defined and configured; but multiple + sorting indexes can be specified dynamically at search + time. Ranking does not need to use specific indexes, so + dynamic ranking can be enabled and disabled without + re-indexing; whereas, sorting indexes need to be + defined before indexing. + + + + + + + + + Extended Services: Remote Insert, Update and Delete + + + + Extended services are only supported when accessing the &zebra; + server using the &acro.z3950; + protocol. The &acro.sru; protocol does + not support extended services. + + + + + The extended services are not enabled by default in zebra - due to the + fact that they modify the system. &zebra; can be configured + to allow anybody to + search, and to allow only updates for a particular admin user + in the main zebra configuration file zebra.cfg. + For user admin, you could use: + + perm.anonymous: r + perm.admin: rw + passwd: passwordfile + + And in the password file + passwordfile, you have to specify users and + encrypted passwords as colon separated strings. + Use a tool like htpasswd + to maintain the encrypted passwords. + + admin:secret + + It is essential to configure &zebra; to store records internally, + and to support + modifications and deletion of records: + + storeData: 1 + storeKeys: 1 + + The general record type should be set to any record filter which + is able to parse &acro.xml; records, you may use any of the two + declarations (but not both simultaneously!) + + recordType: dom.filter_dom_conf.xml + # recordType: grs.xml + + Notice the difference to the specific instructions + + recordType.xml: dom.filter_dom_conf.xml + # recordType.xml: grs.xml + + which only work when indexing XML files from the filesystem using + the *.xml naming convention. + + + To enable transaction safe shadow indexing, + which is extra important for this kind of operation, set + + shadow: directoryname: size (e.g. 1000M) + + See for additional information on + these configuration options. + + + + It is not possible to carry information about record types or + similar to &zebra; when using extended services, due to + limitations of the &acro.z3950; + protocol. Therefore, indexing filters can not be chosen on a + per-record basis. One and only one general &acro.xml; indexing filter + must be defined. + + + + + + + + Extended services in the &acro.z3950; protocol + + + The &acro.z3950; standard allows + servers to accept special binary extended services + protocol packages, which may be used to insert, update and delete + records into servers. These carry control and update + information to the servers, which are encoded in seven package fields: + + + + Extended services &acro.z3950; Package Fields + + + + Parameter + Value + Notes + + + + + type + 'update' + Must be set to trigger extended services + + + action + string + + Extended service action type with + one of four possible values: recordInsert, + recordReplace, + recordDelete, + and specialUpdate + + + + record + &acro.xml; string + An &acro.xml; formatted string containing the record + + + syntax + 'xml' + XML/SUTRS/MARC. GRS-1 not supported. + The default filter (record type) as given by recordType in + zebra.cfg is used to parse the record. + + + recordIdOpaque + string + + Optional client-supplied, opaque record + identifier used under insert operations. + + + + recordIdNumber + positive number + &zebra;'s internal system number, + not allowed for recordInsert or + specialUpdate actions which result in fresh + record inserts. + + + + databaseName + database identifier + + The name of the database to which the extended services should be + applied. + + + + +
+ + + + The action parameter can be any of + recordInsert (will fail if the record already exists), + recordReplace (will fail if the record does not exist), + recordDelete (will fail if the record does not + exist), and + specialUpdate (will insert or update the record + as needed, record deletion is not possible). + + + + During all actions, the + usual rules for internal record ID generation apply, unless an + optional recordIdNumber &zebra; internal ID or a + recordIdOpaque string identifier is assigned. + The default ID generation is + configured using the recordId: from + zebra.cfg. + See . + + + + Setting of the recordIdNumber parameter, + which must be an existing &zebra; internal system ID number, is not + allowed during any recordInsert or + specialUpdate action resulting in fresh record + inserts. + + + + When retrieving existing + records indexed with &acro.grs1; indexing filters, the &zebra; internal + ID number is returned in the field + /*/id:idzebra/localnumber in the namespace + xmlns:id="http://www.indexdata.dk/zebra/", + where it can be picked up for later record updates or deletes. + + + + A new element set for retrieval of internal record + data has been added, which can be used to access minimal records + containing only the recordIdNumber &zebra; + internal ID, or the recordIdOpaque string + identifier. This works for any indexing filter used. + See . + + + + The recordIdOpaque string parameter + is an client-supplied, opaque record + identifier, which may be used under + insert, update and delete operations. The + client software is responsible for assigning these to + records. This identifier will + replace zebra's own automagic identifier generation with a unique + mapping from recordIdOpaque to the + &zebra; internal recordIdNumber. + The opaque recordIdOpaque string + identifiers + are not visible in retrieval records, nor are + searchable, so the value of this parameter is + questionable. It serves mostly as a convenient mapping from + application domain string identifiers to &zebra; internal ID's. + + + + + + + Extended services from yaz-client + + + We can now start a yaz-client admin session and create a database: + + adm-create + ]]> + + Now the Default database was created, + we can insert an &acro.xml; file (esdd0006.grs + from example/gils/records) and index it: + + update insert id1234 esdd0006.grs + ]]> + + The 3rd parameter - id1234 here - + is the recordIdOpaque package field. + + + Actually, we should have a way to specify "no opaque record id" for + yaz-client's update command.. We'll fix that. + + + The newly inserted record can be searched as usual: + + f utah + Sent searchRequest. + Received SearchResponse. + Search was a success. + Number of hits: 1, setno 1 + SearchResult-1: term=utah cnt=1 + records returned: 0 + Elapsed: 0.014179 + ]]> + + + + Let's delete the beast, using the same + recordIdOpaque string parameter: + + update delete id1234 + No last record (update ignored) + Z> update delete 1 esdd0006.grs + Got extended services response + Status: done + Elapsed: 0.072441 + Z> f utah + Sent searchRequest. + Received SearchResponse. + Search was a success. + Number of hits: 0, setno 2 + SearchResult-1: term=utah cnt=0 + records returned: 0 + Elapsed: 0.013610 + ]]> + + + + If shadow register is enabled in your + zebra.cfg, + you must run the adm-commit command + + adm-commit + ]]> + + after each update session in order write your changes from the + shadow to the life register space. + + + + + + Extended services from yaz-php + + + Extended services are also available from the &yaz; &acro.php; client layer. An + example of an &yaz;-&acro.php; extended service transaction is given here: + + A fine specimen of a record'; + + $options = array('action' => 'recordInsert', + 'syntax' => 'xml', + 'record' => $record, + 'databaseName' => 'mydatabase' + ); + + yaz_es($yaz, 'update', $options); + yaz_es($yaz, 'commit', array()); + yaz_wait(); + + if ($error = yaz_error($yaz)) + echo "$error"; + ]]> + + + + + + Extended services debugging guide + + When debugging ES over PHP we recommend the following order of tests: + + + + + + Make sure you have a nice record on your filesystem, which you can + index from the filesystem by use of the zebraidx command. + Do it exactly as you planned, using one of the GRS-1 filters, + or the DOMXML filter. + When this works, proceed. + + + + + Check that your server setup is OK before you even coded one single + line PHP using ES. + Take the same record form the file system, and send as ES via + yaz-client like described in + , + and + remember the -a option which tells you what + goes over the wire! Notice also the section on permissions: + try + + perm.anonymous: rw + + in zebra.cfg to make sure you do not run into + permission problems (but never expose such an insecure setup on the + internet!!!). Then, make sure to set the general + recordType instruction, pointing correctly + to the GRS-1 filters, + or the DOMXML filters. + + + + + If you insist on using the sysno in the + recordIdNumber setting, + please make sure you do only updates and deletes. Zebra's internal + system number is not allowed for + recordInsert or + specialUpdate actions + which result in fresh record inserts. + + + + + If shadow register is enabled in your + zebra.cfg, you must remember running the + + Z> adm-commit + + command as well. + + + + + If this works, then proceed to do the same thing in your PHP script. + + + + + + + + + + + +