2 ## Copyright (c) 2000, Index Data.
4 ## Permission to use, copy, modify, distribute, and sell this software and
5 ## its documentation, in whole or in part, for any purpose, is hereby granted,
8 ## 1. This copyright and permission notice appear in all copies of the
9 ## software and its documentation. Notices of copyright or attribution
10 ## which appear at the beginning of any file must remain unchanged.
12 ## 2. The name of Index Data or the individual authors may not be used to
13 ## endorse or promote products derived from this software without specific
14 ## prior written permission.
16 ## THIS SOFTWARE IS PROVIDED "AS IS" AND WITHOUT WARRANTY OF ANY KIND,
17 ## EXPRESS, IMPLIED, OR OTHERWISE, INCLUDING WITHOUT LIMITATION, ANY
18 ## WARRANTY OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
19 ## IN NO EVENT SHALL INDEX DATA BE LIABLE FOR ANY SPECIAL, INCIDENTAL,
20 ## INDIRECT OR CONSEQUENTIAL DAMAGES OF ANY KIND, OR ANY DAMAGES
21 ## WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER OR
22 ## NOT ADVISED OF THE POSSIBILITY OF DAMAGE, AND ON ANY THEORY OF
23 ## LIABILITY, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE
28 ## $Log: SimpleServer.pm,v $
29 ## Revision 1.14 2002-03-06 11:30:02 mike
30 ## Add RPN structure documentation to SimpleServer.pm's POD.
31 ## Add README to MANIFEST.
33 ## Revision 1.13 2002/03/06 11:02:04 mike
34 ## Added simple README file, derived from POD comments in SimpleServer.pm
35 ## Fixed my (Mike Taylor's) email address
37 ## Revision 1.12 2002/03/05 20:52:22 sondberg
38 ## Version 0.05 so that we can release the thing at CPAN.
40 ## Revision 1.11 2002/03/05 20:49:56 sondberg
41 ## Added a couple of lines of documentation.
43 ## Revision 1.10 2002/02/28 11:21:57 mike
44 ## Add RPN structure to search-handler argument hash.
46 ## Revision 1.9 2001/08/29 11:48:36 sondberg
49 ## Net::Z3950::SimpleServer::ScanSuccess
50 ## Net::Z3950::SimpleServer::ScanPartial
52 ## and a bit of documentation.
54 ## Revision 1.8 2001/08/29 10:29:51 sondberg
55 ## Added some documentation of scan.
57 ## Revision 1.7 2001/08/24 14:00:20 sondberg
58 ## Added support for scan.
60 ## Revision 1.6 2001/03/13 14:17:15 sondberg
61 ## Added support for GRS-1.
64 package Net::Z3950::SimpleServer;
67 use vars qw($VERSION @ISA @EXPORT @EXPORT_OK);
74 @ISA = qw(Exporter AutoLoader DynaLoader);
75 # Items to export into callers namespace by default. Note: do not export
76 # names by default without a very good reason. Use EXPORT_OK instead.
77 # Do not simply export all your public functions/methods/constants.
83 bootstrap Net::Z3950::SimpleServer $VERSION;
85 # Preloaded methods go here.
95 carp "SimpleServer.pm: WARNING: Multithreaded server unsupported";
99 croak "SimpleServer.pm: ERROR: Unspecified search handler" unless defined($self->{SEARCH});
100 croak "SimpleServer.pm: ERROR: Unspecified fetch handler" unless defined($self->{FETCH});
111 if (defined($self->{INIT})) {
112 set_init_handler($self->{INIT});
114 set_search_handler($self->{SEARCH});
115 set_fetch_handler($self->{FETCH});
116 if (defined($self->{CLOSE})) {
117 set_close_handler($self->{CLOSE});
119 if (defined($self->{PRESENT})) {
120 set_present_handler($self->{PRESENT});
122 if (defined($self->{SCAN})) {
123 set_scan_handler($self->{SCAN});
130 # Register packages that we will use in translated RPNs
131 package Net::Z3950::APDU::Query;
132 package Net::Z3950::APDU::OID;
133 package Net::Z3950::RPN::And;
134 package Net::Z3950::RPN::Or;
135 package Net::Z3950::RPN::AndNot;
136 package Net::Z3950::RPN::Term;
137 package Net::Z3950::RPN::Attributes;
138 package Net::Z3950::RPN::Attribute;
140 # Must revert to original package for Autoloader's benefit
141 package Net::Z3950::SimpleServer;
144 # Autoload methods go after =cut, and are processed by the autosplit program.
148 # Below is the stub of documentation for your module. You better edit it!
152 Net::Z3950::SimpleServer - Simple Perl API for building Z39.50 servers.
156 use Net::Z3950::SimpleServer;
158 sub my_search_handler {
161 my $set_id = $args->{SETNAME};
162 my @database_list = @{ $args->{DATABASES} };
163 my $query = $args->{QUERY};
165 ## Perform the query on the specified set of databases
166 ## and return the number of hits:
168 $args->{HITS} = $hits;
171 sub my_fetch_handler { # Get a record for the user
174 my $set_id = $args->{SETNAME};
176 my $record = fetch_a_record($args->{OFFSET});
178 $args->{RECORD} = $record;
179 if (number_of_hits() == $args->{OFFSET}) { ## Last record in set?
187 ## Register custom event handlers:
189 my $z = new Net::Z3950::SimpleServer( INIT => \&my_init_handler,
190 CLOSE => \&my_close_handler,
191 SEARCH => \&my_search_handler,
192 FETCH => \&my_fetch_handler);
195 $z->launch_server("ztest.pl", @ARGV);
199 The SimpleServer module is a tool for constructing Z39.50 "Information
200 Retrieval" servers in Perl. The module is easy to use, but it
201 does help to have an understanding of the Z39.50 query
202 structure and the construction of structured retrieval records.
204 Z39.50 is a network protocol for searching remote databases and
205 retrieving the results in the form of structured "records". It is widely
206 used in libraries around the world, as well as in the US Federal Government.
207 In addition, it is generally useful whenever you wish to integrate a number
208 of different database systems around a shared, asbtract data model.
210 The model of the module is simple: It implements a "generic" Z39.50
211 server, which invokes callback functions supplied by you to search
212 for content in your database. You can use any tools available in
213 Perl to supply the content, including modules like DBI and
216 The server will take care of managing the network connections for
217 you, and it will spawn a new process (or thread, in some
218 environments) whenever a new connection is received.
220 The programmer can specify subroutines to take care of the following type
226 - Fetching of records
227 - Scan request (browsing)
228 - Closing down connection
230 Note that only the Search and Fetch handler functions are required.
231 The module can supply default responses to the other on its own.
233 After the launching of the server, all control is given away from
234 the Perl script to the server. The server calls the registered
235 subroutines to field incoming requests from Z39.50 clients.
237 A reference to an anonymous hash is passed to each handle. Some of
238 the entries of these hashes are to be considered input and others
241 The Perl programmer specifies the event handles for the server by
242 means of the the SimpleServer object constructor
244 my $z = new Net::Z3950::SimpleServer(
245 INIT => \&my_init_handler,
246 CLOSE => \&my_close_handler,
247 SEARCH => \&my_search_handler,
248 PRESENT => \&my_present_handler,
249 SCAN => \&my_scan_handler,
250 FETCH => \&my_fetch_handler);
252 After the custom event handles are declared, the server is launched
253 by means of the method
255 $z->launch_server("MyServer.pl", @ARGV);
257 Notice, the first argument should be the name of your server
258 script (for logging purposes), while the rest of the arguments
259 are documented in the YAZ toolkit manual: The section on
260 application invocation: <http://www.indexdata.dk/yaz/yaz-7.php>
264 The init handler is called whenever a Z39.50 client is attempting
265 to logon to the server. The exchange of parameters between the
266 server and the handler is carried out via an anonymous hash reached
271 The argument hash passed to the init handler has the form
274 ## Response parameters:
276 IMP_NAME => "", ## Z39.50 Implementation name
277 IMP_VER => "", ## Z39.50 Implementation version
278 ERR_CODE => 0, ## Error code, cnf. Z39.50 manual
279 HANDLE => undef ## Handler of Perl data structure
282 The HANDLE member can be used to store any scalar value which will then
283 be provided as input to all subsequent calls (ie. for searching, record
284 retrieval, etc.). A common use of the handle is to store a reference to
285 a hash which may then be used to store session-specific parameters.
286 If you have any session-specific information (such as a list of
287 result sets or a handle to a back-end search engine of some sort),
288 it is always best to store them in a private session structure -
289 rather than leaving them in global variables in your script.
291 The Implementation name and version are only really used by Z39.50
292 client developers to see what kind of server they're dealing with.
293 Filling these in is optional.
295 The ERR_CODE should be left at 0 (the default value) if you wish to
296 accept the connection. Any other value is interpreted as a failure
297 and the client will be shown the door.
299 =head2 Search handler
301 Similarly, the search handler is called with a reference to an anony-
302 mous hash. The structure is the following:
305 ## Request parameters:
307 HANDLE => ref, ## Your session reference.
308 SETNAME => "id", ## ID of the result set
309 REPL_SET => 0, ## Replace set if already existing?
310 DATABASES => ["xxx"], ## Reference to a list of data-
312 QUERY => "query", ## The query expression
313 RPN => $obj, ## Reference to a Net::Z3950::APDU::Query
315 ## Response parameters:
317 ERR_CODE => 0, ## Error code (0=Succesful search)
318 ERR_STR => "", ## Error string
319 HITS => 0 ## Number of matches
322 Note that a search which finds 0 hits is considered successful in
323 Z39.50 terms - you should only set the ERR_CODE to a non-zero value
324 if there was a problem processing the request. The Z39.50 standard
325 provides a comprehensive list of standard diagnostic codes, and you
326 should use these whenever possible.
328 The QUERY is a tree-structure of terms combined by operators, the
329 terms being qualified by lists of attributes. The query is presented
330 to the search function in the Prefix Query Format (PQF) which is
331 used in many applications based on the YAZ toolkit. The full grammar
332 is described in the YAZ manual.
334 The following are all examples of valid queries in the PQF.
340 @or "dylan" "zimmerman"
344 @or @and bob dylan @set Result-1
346 @and @attr 1=1 "bob dylan" @attr 1=4 "slow train coming"
348 @attrset @attr 4=1 @attr 1=4 "self portrait"
350 You will need to write a recursive function or something similar to
351 parse incoming query expressions, and this is usually where a lot of
352 the work in writing a database-backend happens. Fortunately, you don't
353 need to support anymore functionality than you want to. For instance,
354 it is perfectly legal to not accept boolean operators, but you SHOULD
355 try to return good error codes if you run into something you can't or
358 A more convenient alternative to the QUERY member may be the RPN
359 member, which is a reference to a Net::Z3950::APDU::Query object
360 representing the RPN query tree. The structure of that object is
361 supposed to be self-documenting, but here's a brief summary of what
368 C<Net::Z3950::APDU::Query> is a hash with two fields:
374 =item C<attributeSet>
376 Optional. If present, it is a reference to a
377 C<Net::Z3950::APDU::OID>. This is a string of dot-separated integers
378 representing the OID of the query's top-level attribute set.
382 Mandatory: a refererence to the RPN tree itself.
388 Each node of the tree is an object of one of the following types:
394 =item C<Net::Z3950::RPN::And>
396 =item C<Net::Z3950::RPN::Or>
398 =item C<Net::Z3950::RPN::AndNot>
400 These three classes are all arrays of two elements, each of which is a
401 node of one of the above types.
403 =item C<Net::Z3950::RPN::Term>
405 See below for details.
409 (I guess I should make a superclass C<Net::Z3950::RPN::Node> and make
410 all of these subclasses of it. Not done that yet, but will do soon.)
418 C<Net::Z3950::RPN::Term> is a hash with two fields:
426 A string containing the search term itself.
430 A reference to a C<Net::Z3950::RPN::Attributes> object.
436 C<Net::Z3950::RPN::Attributes> is an array of references to
437 C<Net::Z3950::RPN::Attribute> objects. (Note the plural/singular
442 C<Net::Z3950::RPN::Attribute> is a hash with three elements:
448 =item C<attributeSet>
450 Optional. If present, it is dot-separated OID string, as above.
452 =item C<attributeType>
454 An integer indicating the type of the attribute - for example, under
455 the BIB-1 attribute set, type 1 indicates a ``use'' attribute, type 2
456 a ``relation'' attribute, etc.
458 =item C<attributeValue>
460 An integer indicating the value of the attribute - for example, under
461 BIB-1, if the attribute type is 1, then value 4 indictates a title
462 search and 7 indictates an ISBN search; but if the attribute type is
463 2, then value 4 indicates a ``greater than or equal'' search, and 102
464 indicates a relevance match.
470 Note that, at the moment, none of these classes have any methods at
471 all: the blessing into classes is largely just a documentation thing
472 so that, for example, if you do
474 { use Data::Dumper; print Dumper($args->{RPN}) }
476 you get something fairly human-readable. But of course, the type
477 distinction between the three different kinds of boolean node is
480 By adding your own methods to these classes (building what I call
481 ``augmented classes''), you can easily build code that walks the tree
482 of the incoming RPN. Take a look at C<samples/render-search.pl> for a
483 sample implementation of such an augmented classes technique.
486 =head2 Present handler
488 The presence of a present handler in a SimpleServer front-end is optional.
489 Each time a client wishes to retrieve records, the present service is
490 called. The present service allows the origin to request a certain number
491 of records retrieved from a given result set.
492 When the present handler is called, the front-end server should prepare a
493 result set for fetching. In practice, this means to get access to the
494 data from the backend database and store the data in a temporary fashion
495 for fast and efficient fetching. The present handler does *not* fetch
496 anything. This task is taken care of by the fetch handler, which will be
497 called the correct number of times by the YAZ library. More about this
499 If no present handler is implemented in the front-end, the YAZ toolkit
500 will take care of a minimum of preparations itself. This default present
501 handler is sufficient in many situations, where only a small amount of
502 records are expected to be retrieved. If on the other hand, large result
503 sets are likely to occur, the implementation of a reasonable present
504 handler can gain performance significantly.
506 The informations exchanged between client and present handle are:
509 ## Client/server request:
511 HANDLE => ref, ## Reference to datastructure
512 SETNAME => "id", ## Result set ID
513 START => xxx, ## Start position
514 COMP => "", ## Desired record composition
515 NUMBER => yyy, ## Number of requested records
518 ## Respons parameters:
520 HITS => zzz, ## Number of returned records
521 ERR_CODE => 0, ## Error code
522 ERR_STR => "" ## Error message
528 The fetch handler is asked to retrieve a SINGLE record from a given
529 result set (the front-end server will automatically call the fetch
530 handler as many times as required).
532 The parameters exchanged between the server and the fetch handler are
535 ## Client/server request:
537 HANDLE => ref ## Reference to data structure
538 SETNAME => "id" ## ID of the requested result set
539 OFFSET => nnn ## Record offset number
540 REQ_FORM => "n.m.k.l"## Client requested format OID
541 COMP => "xyz" ## Formatting instructions
545 RECORD => "" ## Record string
546 BASENAME => "" ## Origin of returned record
547 LAST => 0 ## Last record in set?
548 ERR_CODE => 0 ## Error code
549 ERR_STR => "" ## Error string
550 SUR_FLAG => 0 ## Surrogate diagnostic flag
551 REP_FORM => "n.m.k.l"## Provided format OID
554 The REP_FORM value has by default the REQ_FORM value but can be set to
555 something different if the handler desires. The BASENAME value should
556 contain the name of the database from where the returned record originates.
557 The ERR_CODE and ERR_STR works the same way they do in the search
558 handler. If there is an error condition, the SUR_FLAG is used to
559 indicate whether the error condition pertains to the record currently
560 being retrieved, or whether it pertains to the operation as a whole
561 (eg. the client has specified a result set which does not exist.)
563 If you need to return USMARC records, you might want to have a look at
564 the MARC module on CPAN, if you don't already have a way of generating
567 NOTE: The record offset is 1-indexed - 1 is the offset of the first
572 A full featured Z39.50 server should support scan (or in some literature
573 browse). The client specifies a starting term of the scan, and the server
574 should return an ordered list of specified length consisting of terms
575 actually occurring in the data base. Each of these terms should be close
576 to or equal to the term originally specified. The quality of scan compared
577 to simple search is a guarantee of hits. It is simply like browsing through
578 an index of a book, you always find something! The parameters exchanged are
583 HANDLE => $ref ## Reference to data structure
584 TERM => 'start', ## The start term
585 NUMBER => xx, ## Number of requested terms
586 POS => yy, ## Position of starting point
587 ## within returned list
588 STEP => 0, ## Step size
592 ERR_CODE => 0, ## Error code
593 ERR_STR => '', ## Diagnostic message
594 NUMBER => zz, ## Number of returned terms
595 STATUS => $status, ## ScanSuccess/ScanFailure
596 ENTRIES => $entries ## Referenced list of terms
599 where the term list is returned by reference in the scalar $entries, which
600 should point at a data structure of this kind,
606 { TERM => 'energy density',
609 { TERM => 'energy flow',
617 The $status flag should be assigned one of two values:
619 Net::Z3950::SimpleServer::ScanSuccess On success (default)
620 Net::Z3950::SimpleServer::ScanPartial Less terms returned than requested
622 The STEP member contains the requested number of entries in the term-list
623 between two adjacent entries in the response.
627 The argument hash recieved by the close handler has one element only:
631 HANDLE => ref ## Reference to data structure
634 What ever data structure the HANDLE value points at goes out of scope
635 after this call. If you need to close down a connection to your server
636 or something similar, this is the place to do it.
640 Anders Sønderberg (sondberg@indexdata.dk) and Sebastian Hammer
641 (quinn@indexdata.dk). Substantial contributions made by Mike Taylor
642 (mike@miketaylor.org.uk).
646 Any Perl module which is useful for accessing the database of your