From 3d60205d934852596d8939b4db1114ec53a9d2f4 Mon Sep 17 00:00:00 2001 From: Marc Cromme Date: Wed, 14 Jun 2006 12:20:06 +0000 Subject: [PATCH] added extra information on zebra extentions to the bib1 attribute set model --- doc/querymodel.xml | 1411 ++++++++++++++++++++++++++++++---------------------- 1 file changed, 817 insertions(+), 594 deletions(-) diff --git a/doc/querymodel.xml b/doc/querymodel.xml index 20e6b4b..8852fc7 100644 --- a/doc/querymodel.xml +++ b/doc/querymodel.xml @@ -1,10 +1,10 @@ - - - Query Model - + + + Query Model + Query Model Overview - + Zebra is born as a networking Information Retrieval engine adhering to the international standards @@ -25,7 +25,7 @@ PQN, and is thoroughly explained in . - + In addition, Zebra can be configured to understand and map the Common Query Language @@ -34,120 +34,118 @@ representation in . - - + + Prefix Query Format structure and syntax - The - PQF - grammer is documented in the YAZ manual, and shall not be - repeated here. - This textual PQF representation + The PQF grammer + is documented in the YAZ manual, and shall not be + repeated here. This textual PQF representation is always during search mapped to the equivalent Zebra internal query parse tree. - + PQF tree structure - - The PQF parse tree - or the equivalent textual representation - - may start with one specification of the - attribute set used. Following is a query - tree, which - consists of atomic query parts, eventually - paired by boolean binary operators, and - finally recursively combined into - complex query trees. - - - - Attribute sets + The PQF parse tree - or the equivalent textual representation - + may start with one specification of the + attribute set used. Following is a query + tree, which + consists of atomic query parts, eventually + paired by boolean binary operators, and + finally recursively combined into + complex query trees. + + + + Attribute sets + Attribute sets define the exact meaning and semantics of queries issued. Zebra comes with some predefined attribute set definitions, others can easily be defined and added to the configuration. - The Zebra internal query procesing is modeled after - the Bib1 attribute set, and the non-use - attributes type 2-9 are hard-wired in. It is therefore essential - to be familiar with . - - - - - - - - - - - - - - - - - - - - - - - -
Attribute sets predefined in Zebra
exp-1Explain attribute setSpecial attribute set used on the special automagic - IR-Explain-1 database to gain information on - server capabilities, database names, and database - and semantics.
bib-1Bib1 attribute setStandard PQF query language attribute set which defines the - semantics of Z39.50 searching. In addition, all of the - non-use attributes (type 2-9) define the Zebra internal query - processing
gilsGILS attribute setExtention to the Bib1 attribute set.
- - - - Boolean operators - + The Zebra internal query procesing is modeled after + the Bib1 attribute set, and the non-use + attributes type 2-9 are hard-wired in. It is therefore essential + to be familiar with . + + + + + + + + + + + + + + + + + + + + + + + +
Attribute sets predefined in Zebra
exp-1Explain attribute setSpecial attribute set used on the special automagic + IR-Explain-1 database to gain information on + server capabilities, database names, and database + and semantics.
bib-1Bib1 attribute setStandard PQF query language attribute set which defines the + semantics of Z39.50 searching. In addition, all of the + non-use attributes (type 2-9) define the Zebra internal query + processing
gilsGILS attribute setExtention to the Bib1 attribute set.
+ + + + Boolean operators + A pair of subquery trees, or of atomic queries, is combined using the standard boolean operators into new query trees. - - - - - - - - - - - - - - - - - - - - - - - -
Boolean operators
@andbinary AND operatorSet intersection of two atomic queries hit sets
@orbinary OR operatorSet union of two atomic queries hit sets
@notbinary AND NOT operatorSet complement of two atomic queries hit sets
@proxbinary PROXIMY operatorSet intersection of two atomic queries hit sets. In - addition, the intersection set is purged for all - documents which do not satisfy the requested query - term proximity. Usually a proper subset of the AND - operation.
- - + + + + + + + + + + + + + + + + + + + + + + + +
Boolean operators
@andbinary AND operatorSet intersection of two atomic queries hit sets
@orbinary OR operatorSet union of two atomic queries hit sets
@notbinary AND NOT operatorSet complement of two atomic queries hit sets
@proxbinary PROXIMY operatorSet intersection of two atomic queries hit sets. In + addition, the intersection set is purged for all + documents which do not satisfy the requested query + term proximity. Usually a proper subset of the AND + operation.
+ + For example, we can combine the terms information and retrieval into different searches in the default index of the default @@ -155,115 +153,115 @@ Querying for the union of all documents containing the terms information OR retrieval: - - @or information retrieval - - - + + Z> find @or information retrieval + + + Querying for the intersection of all documents containing the terms information AND retrieval: The hit set is a subset of the coresponding OR query. - - @and information retrieval - - - + + Z> find @and information retrieval + + + Querying for the intersection of all documents containing the terms information AND retrieval, taking proximity into account: The hit set is a subset of the coresponding AND query. - - @prox information retrieval - - - + + Z> find @prox information retrieval + + + Querying for the intersection of all documents containing the terms information AND retrieval, in the same order and near each other as described in the term list The hit set is a subset of the coresponding PROXIMY query. - - "information retrieval" - - - - - - - Atomic queries - + + Z> find "information retrieval" + + + + + + + Atomic queries + Atomic queries are the query parts which work on one acess point only. These consist of an attribute list followed by a single term or a quoted term list. - - + + Unsupplied non-use attributes type 2-9 are either inherited from higher nodes in the query tree, or are set to Zebra's default values. See for details. - - - - - - - - - + +
Atomic queries
attribute listList of orthogonal attributesAny of the orthogonal attribute types may be omitted, + + + + + + + + + - - - - + + + + - - -
Atomic queries
attribute listList of orthogonal attributesAny of the orthogonal attribute types may be omitted, these are inherited from higher query tree nodes, or if not inherited, are set to the default Zebra configuration values. -
termsingle term - or quoted term list Here the search terms or list of search terms is added +
termsingle term + or quoted term list Here the search terms or list of search terms is added to the query
- +
+ Querying for the term information in the default index using the default attribite set, the server choice of access point/index, and the default non-use attributes. - - "information" - - - - Equivalent query fully specified: - @attrset bib-1 @attr 1=1017 @attr 2=3 @attr 3=3 @attr 4=1 @attr 5=100 @attr 6=1 "information" + Z> find "information" - - - - Finding all documents which have empty titles. Notice that the - empty term must be quoted, but is otherwise legal. + + + Equivalent query fully specified: - @attr 1=4 "" + Z> find @attrset bib-1 @attr 1=1017 @attr 2=3 @attr 3=3 @attr 4=1 @attr 5=100 @attr 6=1 "information" - - - + + + + Finding all documents which have empty titles. Notice that the + empty term must be quoted, but is otherwise legal. + + Z> find @attr 1=4 "" + + + + - Zebra's special use attribute of type 'string' + Zebra's special use attribute type 1 of form 'string' The numeric use (type 1) attribute is usually - refered to from a given + refered to from a given attribute set. In addition, Zebra let you use any internal index - name defined in your configuration - as use atribute value. This is a great feature for + name defined in your configuration + as use atribute value. This is a great feature for debugging, and when you do not need the complecity of defined use attribute values. It is the preferred way of accessing Zebra indexes directly. @@ -272,15 +270,15 @@ Finding all documents which have the term list "information retrieval" in an Zebra index, using it's internal full string name. - @attr 1=sometext "information retrieval" + Z> find @attr 1=sometext "information retrieval" - + Searching the bib-1 use attribute 54 using it's string name: - @attr 1=Code-language eng + Z> find @attr 1=Code-language eng - + Searching in any silly string index - if it's defined in your indexation rules and can be parsed by the PQF parser. @@ -288,21 +286,116 @@ this facility, as it might confuse your users with some very unexpected results. - @attr 1=silly/xpath/alike[@index]/name "information retrieval" + Z> find @attr 1=silly/xpath/alike[@index]/name "information retrieval" - - + + See for details, and - + for the SRU PQF query extention using string names as a fast - debugging facility. - - - - - - - Explain Attribute Set + debugging facility. + + + + + Zebra's special use attribute type 1 of form 'XPath' + for GRS filters + + As we have seen above, it is possible (albeit seldom a great + idea) to emulate + XPath 1.0 based + search by defining use (type 1) + string attributes which in appearence + resemble XPath queries. There are two + problems with this approach: first, the XPath-look-alike has to + be defined at indexation time, no new undefined + XPath queries can entered at search time, and second, it might + confuse users very much that an XPath-alike index name in fact + gets populated from a possible entirely different XML element + than it pretends to acess. + + + When using the GRS Record Model + (see ), we have the + possibility to embed life + XPath expressions + in the PQF queries, which are here called + use (type 1) xpath + attributes. You must enable the + xpath enable directive in your + .abs config files. + + + Only a very restricted subset of the + XPath 1.0 + standard is supported as the GRS record model is simpler than + a full XML DOM structure. See the following examples for + possibilities. + + + Finding all documents which have the term "content" + inside a text node found in a specific XML DOM + subtree, whose starting element is + adressed by XPath. + + Z> find @attr 1=/root content + Z> find @attr 1=/root/first content + + Notice that the + XPath must be absolute, i.e., must start with '/', and that the + XPath decendant-or-self axis followed by a + text node selection text() is implicitly + appended to the stated XPath. + + It follows that the above searches are interpreted as: + + Z> find @attr 1=/root//text() content + Z> find @attr 1=/root/first//text() content + + + + + Filter the adressing XPath by a predicate working on exact + string values in + attributes (in the XML sense) can be done: return all those docs which + have the term "english" contained in one of all text subnodes of + the subtree defined by the XPath + /record/title[@lang='en'] + + Z> find @attr 1=/record/title[@lang='en'] english + + + + + Combining numeric indexes, boolean expressions, + and xpath based searches is possible: + + Z> find @attr 1=/record/title @and foo bar + Z> find @and @attr 1=/record/title foo @attr 1=4 bar + + + + Escaping PQF keywords and other non-parseable XPath constructs + with '{ }' to prevent syntax errors: + + Z> find @attr {1=/root/first[@attr='danish']} content + Z> find @attr {1=/root/second[@attr='danish lake']} + Z> find @attr {1=/root/third[@attr='dansk s\xc3\xb8']} + + + + It is worth mentioning that these dynamic performed XPath + queries are a performance bottelneck, as no optimized + specialized indexes can be used. Therefore, avoid the use of + this facility when speed is essential, and the database content + size is medium to large. + + + + + + + Explain Attribute Set The Z39.50 standard defines the Explainattribute set @@ -315,8 +408,8 @@ The attribute-set exp-1 consists of a single Use (type 1) attribute. - - + + In addition, the non-Use bib-1 attributes, that is, the types Relation, Position, @@ -324,57 +417,58 @@ and Completeness are imported from the bib-1 attribute set, and may be used within any explain query. - + - + Use Attributes (type = 1) - - The following Explain search atributes are supported: - ExplainCategory (@attr 1=1), - DatabaseName (@attr 1=3), - DateAdded (@attr 1=9), - DateChanged(@attr 1=10). - - - A search in the use attribute ExplainCategory - supports only these predefined values: - CategoryList, TargetInfo, - DatabaseInfo, AttributeDetails. - + + The following Explain search atributes are supported: + ExplainCategory (@attr 1=1), + DatabaseName (@attr 1=3), + DateAdded (@attr 1=9), + DateChanged(@attr 1=10). + + + A search in the use attribute ExplainCategory + supports only these predefined values: + CategoryList, TargetInfo, + DatabaseInfo, AttributeDetails. + See tab/explain.att and the + Z39.50 standard for more information. - - + + Explain searches with yaz-client - - Classic Explain only defines retrieval of Explain information - via ASN.1. Pratically no Z39.50 clients supports this. Fortunately - they don't have to - Zebra allows retrieval of this information - in other formats: - SUTRS, XML, - GRS-1 and ASN.1 Explain. - - + + Classic Explain only defines retrieval of Explain information + via ASN.1. Pratically no Z39.50 clients supports this. Fortunately + they don't have to - Zebra allows retrieval of this information + in other formats: + SUTRS, XML, + GRS-1 and ASN.1 Explain. + + List supported categories to find out which explain commands are supported: Z> base IR-Explain-1 - Z> @attr exp1 1=1 categorylist + Z> find @attr exp1 1=1 categorylist Z> form sutrs Z> show 1+2 - + Get target info, that is, investigate which databases exist at this server endpoint: Z> base IR-Explain-1 - Z> @attr exp1 1=1 targetinfo + Z> find @attr exp1 1=1 targetinfo Z> form xml Z> show 1+1 Z> form grs-1 @@ -383,7 +477,7 @@ Z> show 1+1 - + List all supported databases, the number of hits is the number of databases found, which most commonly are the @@ -392,7 +486,7 @@ IR-Explain-1 databases. Z> base IR-Explain-1 - Z> f @attr exp1 1=1 databaseinfo + Z> find @attr exp1 1=1 databaseinfo Z> form sutrs Z> show 1+2 @@ -402,15 +496,15 @@ Get database info record for database Default. Z> base IR-Explain-1 - Z> @and @attr exp1 1=1 databaseinfo @attr exp1 1=3 Default + Z> find @and @attr exp1 1=1 databaseinfo @attr exp1 1=3 Default Identical query with explicitly specified attribute set: Z> base IR-Explain-1 - Z> @attrset exp1 @and @attr 1=1 databaseinfo @attr 1=3 Default + Z> find @attrset exp1 @and @attr 1=1 databaseinfo @attr 1=3 Default - + Get attribute details record for database Default. @@ -420,320 +514,345 @@ found. Z> base IR-Explain-1 - Z> @and @attr exp1 1=1 attributedetails @attr exp1 1=3 Default + Z> find @and @attr exp1 1=1 attributedetails @attr exp1 1=3 Default Identical query with explicitly specified attribute set: Z> base IR-Explain-1 - Z> @attrset exp1 @and @attr 1=1 attributedetails @attr 1=3 Default + Z> find @attrset exp1 @and @attr 1=1 attributedetails @attr 1=3 Default - - - - - Bib1 Attribute Set - - Something about querying to be written .. - - - Most of the information contained in this section is an excerpt of - the ATTRIBUTE SET BIB-1 (Z39.50-1995) - SEMANTICS, found at The BIB-1 - Attribute Set Semantics from 1995, also in an updated - Bib-1 - Attribute Set - version from 2003. Index Data is not the copyright holder of this - information. - + + + + + Bib1 Attribute Set + + Something about querying to be written .. + + + Most of the information contained in this section is an excerpt of + the ATTRIBUTE SET BIB-1 (Z39.50-1995) + SEMANTICS, + found at . The BIB-1 + Attribute Set Semantics from 1995, also in an updated + Bib-1 + Attribute Set + version from 2003. Index Data is not the copyright holder of this + information. + - Use Attributes (type = 1) - - - - Relation Attributes (type = 2) - - - - - - Position Attributes (type = 3) - - - - Structure Attributes (type = 4) - - - - Truncation Attributes (type = 5) - - - - Completeness Attributes (type = 6) - - - - Zebra Extention Sorting Attributes (type = 7) - - - - Zebra Extention Search Estimation Attributes (type = 8) - - - - Zebra Extention Weight Attributes (type = 9) - - - - - - Mapping from Bib1 Attributes to Zebra internal - register indexes - - - - - 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. - + Use Attributes (type = 1) + - - For the Truncation attribute, - No Truncation is the default. - Left Truncation is not supported. - Process # in search term 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. - - + + Phrase search for information retrieval in + the title-register: + + Z> find @attr 1=4 "information retrieval" + + - - Regular expressions + + Relation Attributes (type = 2) + - 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 zero or once. 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. + Ranked search for information retrieval in + the title-register + (see for the glory details): + + Z> find @attr 1=4 @attr 2=102 "information retrieval" + + + + Position Attributes (type = 3) + + + + Structure Attributes (type = 4) + + - Since the plus operator is normally a suffix operator the addition to - the query syntax doesn't violate the syntax for standard regular - expressions. + For example, 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: + + Z> find @attr 4=109 @attr 2=5 @attr gils 1=2038 -114 + + + Truncation Attributes (type = 5) + + + + Completeness Attributes (type = 6) + + - - Query examples + + Zebra specific Search Extentions to all Attribute Sets + + Zebra extends the Bib1 attribute types, and these extentions are + recognized regardless of attribute + set used in a search operation query. + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + +
Zebra Search Attribute Extentions
Name and TypeOperationZebra version
Embedded Sort (type 7)search1.1
Term Set (type 8)search1.1
Rank weight (type 9)search1.1
Approx Limit (type 9)search1.4
Term Reference (type 10)search1.4
+ + + Zebra Extention Embedded Sort Attribute (type 7) + - Phrase search for information retrieval in - the title-register: + The embedded sort is a way to specify sort within a query - thus + removing the need to send a Sort Request separately. It is both + faster and does not require clients to deal with the Sort + Facility. + + + The possible values after attribute type 7 are + 1 ascending and + 2 descending. + The attributes+term (APT) node is separate from the + rest and must be @or'ed. + The term associated with APT is the sorting level in integers, + where 0 means primary sort, + 1 means secondary sort, and so forth. + See also . + + + For example, searching for water, sort by title (ascending) - @attr 1=4 "information retrieval" + Z> find @or @attr 1=1016 water @attr 7=1 @attr 1=4 0 - - Ranked search for the same thing: + Or, searching for water, sort by title ascending, then date descending - @attr 1=4 @attr 2=102 "Information retrieval" + Z> find @or @or @attr 1=1016 water @attr 7=1 @attr 1=4 0 @attr 7=2 @attr 1=30 1 + + + + + Zebra Extention Term Set Attribute (type 8) + + + The Term Set feature is a facility that allows a search to store + hitting terms in a "pseudo" resultset; thus a search (as usual) + + a scan-like facility. Requires a client that can do named result + sets since the search generates two result sets. The value for + attribute 8 is the name of a result set (string). The terms in + the named term set are returned as SUTRS records. + + + For example, searching for u in title, right truncated, and + storing the result in term set named 'aset' + + Z> find @attr 5=1 @attr 1=4 @attr 8=aset u + + + + The model has one serious flaw: we don't know the size of term + set. Experimental. Do not use in production code. + + + + Zebra Extention Rank Weight Attribute (type 9) + + + Rank weight is a way to pass a value to a ranking algorithm - so + that one APT has one value - while another as a different one. + See also . + + + For example, searching for utah in title with weight 30 as well + as any with weight 20: + + Z> find @attr 2=102 @or @attr 9=30 @attr 1=4 utah @attr 9=20 utah + + Zebra Extention Approximative Limit Attribute (type 9) + + + Newer Zebra versions normally estemiates hit count for every APT + (leaf) in the query tree. These hit counts are returned as part of + the searchResult-1 facility in the binary encoded Z39.50 search + response packages. + + + By setting a limit for the APT we can make Zebra turn into + approximate hit count when a certain hit count limit is + reached. A value of zero means exact hit count. + + + For example, we might be intersted in exact hit count for a, but + for b we allow hit count estimates for 1000 and higher. + + Z> find @and a @attr 9=1000 b + + + + The estimated hit count fascility makes searches faster, as one + only needs to process large hit lists partially. + + + This facility clashes with rank weight, because there all + documents in the hit lists need to be examined for scoring and + re-sorting. + It is an experimental + extention. Do not use in production code. + + + + Zebra Extention Term Reference Attribute (type 10) + + + Zebra supports the searchResult-1 facility. If attribute 10 is + given, that specifies a subqueryId value returned as part of the + search result. It is a way for a client to name an APT part of a + query. + + + + Experimental. Do not use in production code. + + + + + + + Zebra specific Scan Extentions to all Attribute Sets + + Zebra extends the Bib1 attribute types, and these extentions are + recognized regardless of attribute + set used in a scan operation query. + + + + + + + + + + + + + + + + + + + + + + +
Zebra Scan Attribute Extentions
Name and TypeOperationZebra version
Result Set Narrow (type 8)scan1.3
Approximative Limit (type 9)scan1.4
+ + + Zebra Extention Result Set Narrow (type 8) + + + If attribute 8 is given for scan, the value is the name of a + result set. Each hit count in scan is @and'ed with the result set + given. + + + + Experimental and buggy. Definitely not to be used in production code. + + + Zebra Extention Approximative Limit (type 9) + + + The approximative limit (as for search) is a way to enable approx + hit counts for scan hit counts. + + + + Experimental. Do not use in production code. + + + + + + + Mapping from Bib1 Attributes to Zebra internal + register indexes + + TO-DO + + + + + 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 # in search term 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. + + + + + Zebra Regular Expressions in Truncation Attribute (type = 5) + + + Each term in a query is interpreted as a regular expression if + the truncation value is either Regxp-1 (@attr 5=102) + or Regxp-2 (@attr 5=103). + Both query types follow the same syntax with the operands: + + + + + + + + + + + + + + + + + + + +
Regular Expression Operands
xMatches the character x.
.Matches any character.
[ .. ]Matches the set of characters specified; + such as [abc] or [a-c].
+ + + The above operands can be combined with the following operators: + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + +
Regular Expression Operators
x*Matches x zero or more times. + Priority: high.
x+Matches x one or more times. + Priority: high.
x? Matches x zero or once. + 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. + + + + For example, a phrase search with regular expressions in + the title-register is performed like this: + + Z> find @attr 1=4 @attr 5=102 "informat.* retrieval" + + + + + Combinations with other attributes are possible. For example, a + ranked search with a regular expression + (see for the glory details): + + Z> find @attr 1=4 @attr 5=102 @attr 2=102 "informat.* retrieval" + + + + -