1 ## This file is part of simpleserver
2 ## Copyright (C) 2000-2011 Index Data.
3 ## All rights reserved.
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5 ## modification, are permitted provided that the following conditions are met:
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27 package Net::Z3950::SimpleServer;
30 use vars qw($VERSION @ISA @EXPORT @EXPORT_OK);
37 @ISA = qw(Exporter AutoLoader DynaLoader);
41 bootstrap Net::Z3950::SimpleServer $VERSION;
43 # Preloaded methods go here.
53 carp "SimpleServer.pm: WARNING: Multithreaded server unsupported";
57 croak "SimpleServer.pm: ERROR: Unspecified search handler" unless defined($self->{SEARCH});
58 croak "SimpleServer.pm: ERROR: Unspecified fetch handler" unless defined($self->{FETCH});
69 ### This modal internal interface, in which we set a bunch of
70 # globals and then call start_server(), is asking for
71 # trouble. Instead, we should just pass the $self object
72 # as a parameter into start_server().
73 if (defined($self->{GHANDLE})) {
74 set_ghandle($self->{GHANDLE});
76 if (defined($self->{INIT})) {
77 set_init_handler($self->{INIT});
79 set_search_handler($self->{SEARCH});
80 set_fetch_handler($self->{FETCH});
81 if (defined($self->{CLOSE})) {
82 set_close_handler($self->{CLOSE});
84 if (defined($self->{PRESENT})) {
85 set_present_handler($self->{PRESENT});
87 if (defined($self->{SCAN})) {
88 set_scan_handler($self->{SCAN});
90 if (defined($self->{SORT})) {
91 set_sort_handler($self->{SORT});
93 if (defined($self->{EXPLAIN})) {
94 set_explain_handler($self->{EXPLAIN});
96 if (defined($self->{DELETE})) {
97 set_delete_handler($self->{DELETE});
99 if (defined($self->{START})) {
100 set_start_handler($self->{START});
106 # Register packages that we will use in translated RPNs
107 package Net::Z3950::RPN::Node;
108 package Net::Z3950::APDU::Query;
109 our @ISA = qw(Net::Z3950::RPN::Node);
110 package Net::Z3950::APDU::OID;
111 package Net::Z3950::RPN::And;
112 our @ISA = qw(Net::Z3950::RPN::Node);
113 package Net::Z3950::RPN::Or;
114 our @ISA = qw(Net::Z3950::RPN::Node);
115 package Net::Z3950::RPN::AndNot;
116 our @ISA = qw(Net::Z3950::RPN::Node);
117 package Net::Z3950::RPN::Term;
118 our @ISA = qw(Net::Z3950::RPN::Node);
119 package Net::Z3950::RPN::RSID;
120 our @ISA = qw(Net::Z3950::RPN::Node);
121 package Net::Z3950::RPN::Attributes;
122 package Net::Z3950::RPN::Attribute;
123 package Net::Z3950::FacetList;
124 package Net::Z3950::FacetField;
125 package Net::Z3950::FacetTerms;
126 package Net::Z3950::FacetTerm;
129 # Utility method for re-rendering Type-1 query back down to PQF
130 package Net::Z3950::RPN::Node;
134 my $class = ref $this;
136 if ($class eq "Net::Z3950::APDU::Query") {
138 my $set = $this->{attributeSet};
139 $res .= "\@attrset $set " if defined $set;
140 return $res . $this->{query}->toPQF();
141 } elsif ($class eq "Net::Z3950::RPN::Or") {
142 return '@or ' . $this->[0]->toPQF() . ' ' . $this->[1]->toPQF();
143 } elsif ($class eq "Net::Z3950::RPN::And") {
144 return '@and ' . $this->[0]->toPQF() . ' ' . $this->[1]->toPQF();
145 } elsif ($class eq "Net::Z3950::RPN::AndNot") {
146 return '@not ' . $this->[0]->toPQF() . ' ' . $this->[1]->toPQF();
147 } elsif ($class eq "Net::Z3950::RPN::RSID") {
148 return '@set ' . $this->{id};
149 } elsif ($class ne "Net::Z3950::RPN::Term") {
150 die "unknown PQF node-type '$class'";
154 foreach my $attr (@{ $this->{attributes} }) {
156 my $set = $attr->{attributeSet};
157 $res .= "$set " if defined $set;
158 $res .= $attr->{attributeType} . "=" . $attr->{attributeValue} . " ";
161 return $res . $this->{term};
165 # Must revert to original package for Autoloader's benefit
166 package Net::Z3950::SimpleServer;
169 # Autoload methods go after =cut, and are processed by the autosplit program.
173 # Below is the stub of documentation for your module. You better edit it!
177 Net::Z3950::SimpleServer - Simple Perl API for building Z39.50 servers.
181 use Net::Z3950::SimpleServer;
183 sub my_search_handler {
186 my $set_id = $args->{SETNAME};
187 my @database_list = @{ $args->{DATABASES} };
188 my $query = $args->{QUERY};
190 ## Perform the query on the specified set of databases
191 ## and return the number of hits:
193 $args->{HITS} = $hits;
196 sub my_fetch_handler { # Get a record for the user
199 my $set_id = $args->{SETNAME};
201 my $record = fetch_a_record($args->{OFFSET});
203 $args->{RECORD} = $record;
204 if (number_of_hits() == $args->{OFFSET}) { ## Last record in set?
211 ## Register custom event handlers:
212 my $z = new Net::Z3950::SimpleServer(GHANDLE = $someObject,
213 INIT => \&my_init_handler,
214 CLOSE => \&my_close_handler,
215 SEARCH => \&my_search_handler,
216 FETCH => \&my_fetch_handler);
219 $z->launch_server("ztest.pl", @ARGV);
223 The SimpleServer module is a tool for constructing Z39.50 "Information
224 Retrieval" servers in Perl. The module is easy to use, but it
225 does help to have an understanding of the Z39.50 query
226 structure and the construction of structured retrieval records.
228 Z39.50 is a network protocol for searching remote databases and
229 retrieving the results in the form of structured "records". It is widely
230 used in libraries around the world, as well as in the US Federal Government.
231 In addition, it is generally useful whenever you wish to integrate a number
232 of different database systems around a shared, abstract data model.
234 The model of the module is simple: It implements a "generic" Z39.50
235 server, which invokes callback functions supplied by you to search
236 for content in your database. You can use any tools available in
237 Perl to supply the content, including modules like DBI and
240 The server will take care of managing the network connections for
241 you, and it will spawn a new process (or thread, in some
242 environments) whenever a new connection is received.
244 The programmer can specify subroutines to take care of the following type
247 - Start service (called once).
251 - Fetching of records
252 - Scan request (browsing)
253 - Closing down connection
255 Note that only the Search and Fetch handler functions are required.
256 The module can supply default responses to the other on its own.
258 After the launching of the server, all control is given away from
259 the Perl script to the server. The server calls the registered
260 subroutines to field incoming requests from Z39.50 clients.
262 A reference to an anonymous hash is passed to each handler. Some of
263 the entries of these hashes are to be considered input and others
266 The Perl programmer specifies the event handlers for the server by
267 means of the SimpleServer object constructor
269 my $z = new Net::Z3950::SimpleServer(
270 START => \&my_start_handler,
271 INIT => \&my_init_handler,
272 CLOSE => \&my_close_handler,
273 SEARCH => \&my_search_handler,
274 PRESENT => \&my_present_handler,
275 SCAN => \&my_scan_handler,
276 FETCH => \&my_fetch_handler,
277 EXPLAIN => \&my_explain_handler,
278 DELETE => \&my_delete_handler,
279 SORT => \&my_sort_handler);
281 In addition, the arguments to the constructor may include GHANDLE, a
282 global handle which is made available to each invocation of every
283 callback function. This is typically a reference to either a hash or
286 If you want your SimpleServer to start a thread (threaded mode) to
287 handle each incoming Z39.50 request instead of forking a process
288 (forking mode), you need to register the handlers by symbol rather
289 than by code reference. Thus, in threaded mode, you will need to
290 register your handlers this way:
292 my $z = new Net::Z3950::SimpleServer(
293 INIT => "my_package::my_init_handler",
294 CLOSE => "my_package::my_close_handler",
298 where my_package is the Perl package in which your handler is
301 After the custom event handlers are declared, the server is launched
302 by means of the method
304 $z->launch_server("MyServer.pl", @ARGV);
306 Notice, the first argument should be the name of your server
307 script (for logging purposes), while the rest of the arguments
308 are documented in the YAZ toolkit manual: The section on
309 application invocation: <http://indexdata.com/yaz/doc/server.invocation.tkl>
311 In particular, you need to use the -T switch to start your SimpleServer
316 The start handler is called when service is started. The argument hash
317 passed to the start handler has the form
320 CONFIG => "default-config" ## GFS config (as given by -c)
324 The purpose of the start handler is to read the configuration file
325 for the Generic Frontend Server . This is specified by option -c.
326 If -c is omitted, the configuration file is set to "default-config".
328 The start handler is optional. It is supported in Simpleserver 1.16 and
333 The init handler is called whenever a Z39.50 client is attempting
334 to logon to the server. The exchange of parameters between the
335 server and the handler is carried out via an anonymous hash reached
340 The argument hash passed to the init handler has the form
343 ## Response parameters:
345 PEER_NAME => "", ## Name or IP address of connecting client
346 IMP_ID => "", ## Z39.50 Implementation ID
347 IMP_NAME => "", ## Z39.50 Implementation name
348 IMP_VER => "", ## Z39.50 Implementation version
349 ERR_CODE => 0, ## Error code, cnf. Z39.50 manual
350 ERR_STR => "", ## Error string (additional info.)
351 USER => "xxx" ## If Z39.50 authentication is used,
352 ## this member contains user name
353 PASS => "yyy" ## Under same conditions, this member
354 ## contains the password in clear text
355 GHANDLE => $obj ## Global handler specified at creation
356 HANDLE => undef ## Handler of Perl data structure
359 The HANDLE member can be used to store any scalar value which will then
360 be provided as input to all subsequent calls (ie. for searching, record
361 retrieval, etc.). A common use of the handle is to store a reference to
362 a hash which may then be used to store session-specific parameters.
363 If you have any session-specific information (such as a list of
364 result sets or a handle to a back-end search engine of some sort),
365 it is always best to store them in a private session structure -
366 rather than leaving them in global variables in your script.
368 The Implementation ID, name and version are only really used by Z39.50
369 client developers to see what kind of server they're dealing with.
370 Filling these in is optional.
372 The ERR_CODE should be left at 0 (the default value) if you wish to
373 accept the connection. Any other value is interpreted as a failure
374 and the client will be shown the door, with the code and the
375 associated additional information, ERR_STR returned.
377 =head2 Search handler
379 Similarly, the search handler is called with a reference to an anony-
380 mous hash. The structure is the following:
383 ## Request parameters:
385 GHANDLE => $obj ## Global handler specified at creation
386 HANDLE => ref, ## Your session reference.
387 SETNAME => "id", ## ID of the result set
388 REPL_SET => 0, ## Replace set if already existing?
389 DATABASES => ["xxx"], ## Reference to a list of data-
391 QUERY => "query", ## The query expression
392 RPN => $obj, ## Reference to a Net::Z3950::APDU::Query
394 ## Response parameters:
396 ERR_CODE => 0, ## Error code (0=Successful search)
397 ERR_STR => "", ## Error string
398 HITS => 0 ## Number of matches
401 Note that a search which finds 0 hits is considered successful in
402 Z39.50 terms - you should only set the ERR_CODE to a non-zero value
403 if there was a problem processing the request. The Z39.50 standard
404 provides a comprehensive list of standard diagnostic codes, and you
405 should use these whenever possible.
407 The QUERY is a tree-structure of terms combined by operators, the
408 terms being qualified by lists of attributes. The query is presented
409 to the search function in the Prefix Query Format (PQF) which is
410 used in many applications based on the YAZ toolkit. The full grammar
411 is described in the YAZ manual.
413 The following are all examples of valid queries in the PQF.
419 @or "dylan" "zimmerman"
423 @or @and bob dylan @set Result-1
425 @and @attr 1=1 "bob dylan" @attr 1=4 "slow train coming"
427 @attrset @attr 4=1 @attr 1=4 "self portrait"
429 You will need to write a recursive function or something similar to
430 parse incoming query expressions, and this is usually where a lot of
431 the work in writing a database-backend happens. Fortunately, you don't
432 need to support anymore functionality than you want to. For instance,
433 it is perfectly legal to not accept boolean operators, but you SHOULD
434 try to return good error codes if you run into something you can't or
437 A more convenient alternative to the QUERY member may be the RPN
438 member, which is a reference to a Net::Z3950::APDU::Query object
439 representing the RPN query tree. The structure of that object is
440 supposed to be self-documenting, but here's a brief summary of what
447 C<Net::Z3950::APDU::Query> is a hash with two fields:
453 =item C<attributeSet>
455 Optional. If present, it is a reference to a
456 C<Net::Z3950::APDU::OID>. This is a string of dot-separated integers
457 representing the OID of the query's top-level attribute set.
461 Mandatory: a reference to the RPN tree itself.
467 Each node of the tree is an object of one of the following types:
473 =item C<Net::Z3950::RPN::And>
475 =item C<Net::Z3950::RPN::Or>
477 =item C<Net::Z3950::RPN::AndNot>
479 These three classes are all arrays of two elements, each of which is a
480 node of one of the above types.
482 =item C<Net::Z3950::RPN::Term>
484 See below for details.
486 =item C<Net::Z3950::RPN::RSID>
488 A reference to a result-set ID indicating a previous search. The ID
489 of the result-set is in the C<id> element.
499 C<Net::Z3950::RPN::Term> is a hash with two fields:
507 A string containing the search term itself.
511 A reference to a C<Net::Z3950::RPN::Attributes> object.
517 C<Net::Z3950::RPN::Attributes> is an array of references to
518 C<Net::Z3950::RPN::Attribute> objects. (Note the plural/singular
523 C<Net::Z3950::RPN::Attribute> is a hash with three elements:
529 =item C<attributeSet>
531 Optional. If present, it is dot-separated OID string, as above.
533 =item C<attributeType>
535 An integer indicating the type of the attribute - for example, under
536 the BIB-1 attribute set, type 1 indicates a ``use'' attribute, type 2
537 a ``relation'' attribute, etc.
539 =item C<attributeValue>
541 An integer or string indicating the value of the attribute - for example, under
542 BIB-1, if the attribute type is 1, then value 4 indicates a title
543 search and 7 indicates an ISBN search; but if the attribute type is
544 2, then value 4 indicates a ``greater than or equal'' search, and 102
545 indicates a relevance match.
551 All of these classes except C<Attributes> and C<Attribute> are
552 subclasses of the abstract class C<Net::Z3950::RPN::Node>. That class
553 has a single method, C<toPQF()>, which may be used to turn an RPN
554 tree, or part of one, back into a textual prefix query.
556 Note that, apart to C<toPQF()>, none of these classes have any methods at
557 all: the blessing into classes is largely just a documentation thing
558 so that, for example, if you do
560 { use Data::Dumper; print Dumper($args->{RPN}) }
562 you get something fairly human-readable. But of course, the type
563 distinction between the three different kinds of boolean node is
566 By adding your own methods to these classes (building what I call
567 ``augmented classes''), you can easily build code that walks the tree
568 of the incoming RPN. Take a look at C<samples/render-search.pl> for a
569 sample implementation of such an augmented classes technique.
572 =head2 Present handler
574 The presence of a present handler in a SimpleServer front-end is optional.
575 Each time a client wishes to retrieve records, the present service is
576 called. The present service allows the origin to request a certain number
577 of records retrieved from a given result set.
578 When the present handler is called, the front-end server should prepare a
579 result set for fetching. In practice, this means to get access to the
580 data from the backend database and store the data in a temporary fashion
581 for fast and efficient fetching. The present handler does *not* fetch
582 anything. This task is taken care of by the fetch handler, which will be
583 called the correct number of times by the YAZ library. More about this
585 If no present handler is implemented in the front-end, the YAZ toolkit
586 will take care of a minimum of preparations itself. This default present
587 handler is sufficient in many situations, where only a small amount of
588 records are expected to be retrieved. If on the other hand, large result
589 sets are likely to occur, the implementation of a reasonable present
590 handler can gain performance significantly.
592 The information exchanged between client and present handle is:
595 ## Client/server request:
597 GHANDLE => $obj ## Global handler specified at creation
598 HANDLE => ref, ## Reference to datastructure
599 SETNAME => "id", ## Result set ID
600 START => xxx, ## Start position
601 COMP => "", ## Desired record composition
602 NUMBER => yyy, ## Number of requested records
605 ## Response parameters:
607 HITS => zzz, ## Number of returned records
608 ERR_CODE => 0, ## Error code
609 ERR_STR => "" ## Error message
615 The fetch handler is asked to retrieve a SINGLE record from a given
616 result set (the front-end server will automatically call the fetch
617 handler as many times as required).
619 The parameters exchanged between the server and the fetch handler are
622 ## Client/server request:
624 GHANDLE => $obj ## Global handler specified at creation
625 HANDLE => ref ## Reference to data structure
626 SETNAME => "id" ## ID of the requested result set
627 OFFSET => nnn ## Record offset number
628 REQ_FORM => "n.m.k.l"## Client requested format OID
629 COMP => "xyz" ## Formatting instructions
630 SCHEMA => "abc" ## Requested schema, if any
634 RECORD => "" ## Record string
635 BASENAME => "" ## Origin of returned record
636 LAST => 0 ## Last record in set?
637 ERR_CODE => 0 ## Error code
638 ERR_STR => "" ## Error string
639 SUR_FLAG => 0 ## Surrogate diagnostic flag
640 REP_FORM => "n.m.k.l"## Provided format OID
641 SCHEMA => "abc" ## Provided schema, if any
644 The REP_FORM value has by default the REQ_FORM value but can be set to
645 something different if the handler desires. The BASENAME value should
646 contain the name of the database from where the returned record originates.
647 The ERR_CODE and ERR_STR works the same way they do in the search
648 handler. If there is an error condition, the SUR_FLAG is used to
649 indicate whether the error condition pertains to the record currently
650 being retrieved, or whether it pertains to the operation as a whole
651 (eg. the client has specified a result set which does not exist.)
653 If you need to return USMARC records, you might want to have a look at
654 the MARC module on CPAN, if you don't already have a way of generating
657 NOTE: The record offset is 1-indexed - 1 is the offset of the first
662 A full featured Z39.50 server should support scan (or in some literature
663 browse). The client specifies a starting term of the scan, and the server
664 should return an ordered list of specified length consisting of terms
665 actually occurring in the data base. Each of these terms should be close
666 to or equal to the term originally specified. The quality of scan compared
667 to simple search is a guarantee of hits. It is simply like browsing through
668 an index of a book, you always find something! The parameters exchanged are
673 GHANDLE => $obj, ## Global handler specified at creation
674 HANDLE => $ref, ## Reference to data structure
675 DATABASES => ["xxx"], ## Reference to a list of data-
677 TERM => 'start', ## The start term
678 RPN => $obj, ## Reference to a Net::Z3950::RPN::Term
680 NUMBER => xx, ## Number of requested terms
681 POS => yy, ## Position of starting point
682 ## within returned list
683 STEP => 0, ## Step size
687 ERR_CODE => 0, ## Error code
688 ERR_STR => '', ## Diagnostic message
689 NUMBER => zz, ## Number of returned terms
690 STATUS => $status, ## ScanSuccess/ScanFailure
691 ENTRIES => $entries ## Referenced list of terms
694 where the term list is returned by reference in the scalar $entries, which
695 should point at a data structure of this kind,
701 { TERM => 'energy density',
704 { TERM => 'energy flow',
712 The $status flag is only meaningful after a successful scan, and
713 should be assigned one of two values:
715 Net::Z3950::SimpleServer::ScanSuccess Full success (default)
716 Net::Z3950::SimpleServer::ScanPartial Fewer terms returned than requested
718 The STEP member contains the requested number of entries in the term-list
719 between two adjacent entries in the response.
721 A better alternative to the TERM member is the the RPN
722 member, which is a reference to a Net::Z3950::RPN::Term object
723 representing the scan clause. The structure of that object is the
724 same as for Term objects included as part of the RPN tree passed to
725 search handlers. This is more useful than the simple TERM because it
726 includes attributes (e.g. access points associated with the term),
727 which are discarded by the TERM element.
731 The argument hash received by the close handler has two elements only:
736 GHANDLE => $obj ## Global handler specified at creation
737 HANDLE => ref ## Reference to data structure
740 What ever data structure the HANDLE value points at goes out of scope
741 after this call. If you need to close down a connection to your server
742 or something similar, this is the place to do it.
744 =head2 Delete handler
746 The argument hash received by the delete handler has the following elements:
750 GHANDLE => $obj, ## Global handler specified at creation
751 HANDLE => ref, ## Reference to data structure
752 SETNAME => "id", ## Result set ID
755 STATUS => 0 ## Deletion status
758 The SETNAME element of the argument hash may or may not be defined.
759 If it is, then SETNAME is the name of a result set to be deleted; if
760 not, then all result-sets associated with the current session should
761 be deleted. In either case, the callback function should report on
762 success or failure by setting the STATUS element either to zero, on
763 success, or to an integer from 1 to 10, to indicate one of the ten
764 possible failure codes described in section 3.2.4.1.4 of the Z39.50
766 http://www.loc.gov/z3950/agency/markup/05.html#Delete-list-statuses1
770 The argument hash received by the sort handler has the following elements:
774 GHANDLE => $obj, ## Global handler specified at creation
775 HANDLE => ref, ## Reference to data structure
776 INPUT => [ a, b ... ], ## Names of result-sets to sort
777 OUTPUT => "name", ## Name of result-set to sort into
778 SEQUENCE ## Sort specification: see below
781 STATUS => 0, ## Success, Partial or Failure
782 ERR_CODE => 0, ## Error code
783 ERR_STR => '', ## Diagnostic message
787 The SEQUENCE element is a reference to an array, each element of which
788 is a hash representing a sort key. Each hash contains the following
795 0 for an ascending sort, 1 for descending, 3 for ascending by
796 frequency, or 4 for descending by frequency.
800 0 for a case-sensitive sort, 1 for case-insensitive
804 How to respond if one or more records in the set to be sorted are
805 missing the fields indicated in the sort specification. 1 to abort
806 the sort, 2 to use a "null value", 3 if a value is provided to use in
807 place of the missing data (although in the latter case, the actual
808 value to use is currently not made available, so this is useless).
812 And one or other of the following:
818 A string indicating the field to be sorted, which the server may
819 interpret as it sees fit (presumably by an out-of-band agreement with
822 =item ELEMENTSPEC_TYPE and ELEMENTSPEC_VALUE
824 I have no idea what this is.
826 =item ATTRSET and SORT_ATTR
828 ATTRSET is the attribute set from which the attributes are taken, and
829 SORT_ATTR is a reference to an array containing the attributes
830 themselves. Each attribute is represented by (are you following this
831 carefully?) yet another hash, this one containing the elements
832 ATTR_TYPE and ATTR_VALUE: for example, type=1 and value=4 in the BIB-1
833 attribute set would indicate access-point 4 which is title, so that a
834 sort of title is requested.
838 Precisely why all of the above is so is not clear, but goes some way
839 to explain why, in the Z39.50 world, the developers of the standard
840 are not so much worshiped as blamed.
842 The backend function should set STATUS to 0 on success, 1 for "partial
843 success" (don't ask) or 2 on failure, in which case ERR_CODE and
844 ERR_STR should be set.
846 =head2 Support for SRU and SRW
848 Since release 1.0, SimpleServer includes support for serving the SRU
849 and SRW protocols as well as Z39.50. These ``web-friendly'' protocols
850 enable similar functionality to that of Z39.50, but by means of rich
851 URLs in the case of SRU, and a SOAP-based web-service in the case of
852 SRW. These protocols are described at
853 http://www.loc.gov/sru
855 In order to serve these protocols from a SimpleServer-based
856 application, it is necessary to launch the application with a YAZ
857 Generic Frontend Server (GFS) configuration file, which can be
858 specified using the command-line argument C<-f> I<filename>. A
859 minimal configuration file looks like this:
863 <cql2rpn>pqf.properties</cql2rpn>
867 This file specifies only that C<pqf.properties> should be used to
868 translate the CQL queries of SRU and SRW into corresponding Z39.50
869 Type-1 queries. For more information about YAZ GFS configuration,
870 including how to specify an Explain record, see the I<Virtual Hosts>
871 section of the YAZ manual at
872 http://indexdata.com/yaz/doc/server.vhosts.tkl
874 The mapping of CQL queries into Z39.50 Type-1 queries is specified by
875 a file that indicates which BIB-1 attributes should be generated for
876 each CQL index, relation, modifiers, etc. A typical section of this
877 file looks like this:
880 index.dc.subject = 1=21
881 index.dc.creator = 1=1003
885 This file specifies the BIB-1 access points (type=1) for the Dublin
886 Core indexes C<title>, C<subject> and C<creator>, and the BIB-1
887 relations (type=2) corresponding to the CQL relations C<E<lt>> and
888 C<E<lt>=>. For more information about the format of this file, see
889 the I<CQL> section of the YAZ manual at
890 http://indexdata.com/yaz/doc/tools.tkl#tools.cql
892 The YAZ distribution include a sample CQL-to-PQF mapping configuration
893 file called C<pqf.properties>; this is sufficient for many
894 applications, and a good base to work from for most others.
896 If a SimpleServer-based application is run without this SRU-specific
897 configuration, it can still serve SRU; however, CQL queries will not
898 be translated, but passed straight through to the search-handler
899 function, as the C<CQL> member of the parameters hash. It is then the
900 responsibility of the back-end application to parse and handle the CQL
901 query, which is most easily done using Ed Summers' fine C<CQL::Parser>
902 module, available from CPAN at
903 http://search.cpan.org/~esummers/CQL-Parser/
907 Anders Sønderberg (sondberg@indexdata.dk),
908 Sebastian Hammer (quinn@indexdata.dk),
909 Mike Taylor (indexdata.com).
911 =head1 COPYRIGHT AND LICENCE
913 Copyright (C) 2000-2011 by Index Data.
915 This library is free software; you can redistribute it and/or modify
916 it under the same terms as Perl itself, either Perl version 5.8.4 or,
917 at your option, any later version of Perl 5 you may have available.
921 Any Perl module which is useful for accessing the data source of your