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 1.15 2002-09-16 14:00:16 sondberg
30 ## Updated Changes and added a few lines of documentation.
32 ## Revision 1.14 2002/03/06 11:30:02 mike
33 ## Add RPN structure documentation to SimpleServer.pm's POD.
34 ## Add README to MANIFEST.
36 ## Revision 1.13 2002/03/06 11:02:04 mike
37 ## Added simple README file, derived from POD comments in SimpleServer.pm
38 ## Fixed my (Mike Taylor's) email address
40 ## Revision 1.12 2002/03/05 20:52:22 sondberg
41 ## Version 0.05 so that we can release the thing at CPAN.
43 ## Revision 1.11 2002/03/05 20:49:56 sondberg
44 ## Added a couple of lines of documentation.
46 ## Revision 1.10 2002/02/28 11:21:57 mike
47 ## Add RPN structure to search-handler argument hash.
49 ## Revision 1.9 2001/08/29 11:48:36 sondberg
52 ## Net::Z3950::SimpleServer::ScanSuccess
53 ## Net::Z3950::SimpleServer::ScanPartial
55 ## and a bit of documentation.
57 ## Revision 1.8 2001/08/29 10:29:51 sondberg
58 ## Added some documentation of scan.
60 ## Revision 1.7 2001/08/24 14:00:20 sondberg
61 ## Added support for scan.
63 ## Revision 1.6 2001/03/13 14:17:15 sondberg
64 ## Added support for GRS-1.
67 package Net::Z3950::SimpleServer;
70 use vars qw($VERSION @ISA @EXPORT @EXPORT_OK);
77 @ISA = qw(Exporter AutoLoader DynaLoader);
78 # Items to export into callers namespace by default. Note: do not export
79 # names by default without a very good reason. Use EXPORT_OK instead.
80 # Do not simply export all your public functions/methods/constants.
86 bootstrap Net::Z3950::SimpleServer $VERSION;
88 # Preloaded methods go here.
98 carp "SimpleServer.pm: WARNING: Multithreaded server unsupported";
102 croak "SimpleServer.pm: ERROR: Unspecified search handler" unless defined($self->{SEARCH});
103 croak "SimpleServer.pm: ERROR: Unspecified fetch handler" unless defined($self->{FETCH});
114 if (defined($self->{INIT})) {
115 set_init_handler($self->{INIT});
117 set_search_handler($self->{SEARCH});
118 set_fetch_handler($self->{FETCH});
119 if (defined($self->{CLOSE})) {
120 set_close_handler($self->{CLOSE});
122 if (defined($self->{PRESENT})) {
123 set_present_handler($self->{PRESENT});
125 if (defined($self->{SCAN})) {
126 set_scan_handler($self->{SCAN});
133 # Register packages that we will use in translated RPNs
134 package Net::Z3950::APDU::Query;
135 package Net::Z3950::APDU::OID;
136 package Net::Z3950::RPN::And;
137 package Net::Z3950::RPN::Or;
138 package Net::Z3950::RPN::AndNot;
139 package Net::Z3950::RPN::Term;
140 package Net::Z3950::RPN::Attributes;
141 package Net::Z3950::RPN::Attribute;
143 # Must revert to original package for Autoloader's benefit
144 package Net::Z3950::SimpleServer;
147 # Autoload methods go after =cut, and are processed by the autosplit program.
151 # Below is the stub of documentation for your module. You better edit it!
155 Net::Z3950::SimpleServer - Simple Perl API for building Z39.50 servers.
159 use Net::Z3950::SimpleServer;
161 sub my_search_handler {
164 my $set_id = $args->{SETNAME};
165 my @database_list = @{ $args->{DATABASES} };
166 my $query = $args->{QUERY};
168 ## Perform the query on the specified set of databases
169 ## and return the number of hits:
171 $args->{HITS} = $hits;
174 sub my_fetch_handler { # Get a record for the user
177 my $set_id = $args->{SETNAME};
179 my $record = fetch_a_record($args->{OFFSET});
181 $args->{RECORD} = $record;
182 if (number_of_hits() == $args->{OFFSET}) { ## Last record in set?
190 ## Register custom event handlers:
192 my $z = new Net::Z3950::SimpleServer( INIT => \&my_init_handler,
193 CLOSE => \&my_close_handler,
194 SEARCH => \&my_search_handler,
195 FETCH => \&my_fetch_handler);
198 $z->launch_server("ztest.pl", @ARGV);
202 The SimpleServer module is a tool for constructing Z39.50 "Information
203 Retrieval" servers in Perl. The module is easy to use, but it
204 does help to have an understanding of the Z39.50 query
205 structure and the construction of structured retrieval records.
207 Z39.50 is a network protocol for searching remote databases and
208 retrieving the results in the form of structured "records". It is widely
209 used in libraries around the world, as well as in the US Federal Government.
210 In addition, it is generally useful whenever you wish to integrate a number
211 of different database systems around a shared, asbtract data model.
213 The model of the module is simple: It implements a "generic" Z39.50
214 server, which invokes callback functions supplied by you to search
215 for content in your database. You can use any tools available in
216 Perl to supply the content, including modules like DBI and
219 The server will take care of managing the network connections for
220 you, and it will spawn a new process (or thread, in some
221 environments) whenever a new connection is received.
223 The programmer can specify subroutines to take care of the following type
229 - Fetching of records
230 - Scan request (browsing)
231 - Closing down connection
233 Note that only the Search and Fetch handler functions are required.
234 The module can supply default responses to the other on its own.
236 After the launching of the server, all control is given away from
237 the Perl script to the server. The server calls the registered
238 subroutines to field incoming requests from Z39.50 clients.
240 A reference to an anonymous hash is passed to each handle. Some of
241 the entries of these hashes are to be considered input and others
244 The Perl programmer specifies the event handles for the server by
245 means of the the SimpleServer object constructor
247 my $z = new Net::Z3950::SimpleServer(
248 INIT => \&my_init_handler,
249 CLOSE => \&my_close_handler,
250 SEARCH => \&my_search_handler,
251 PRESENT => \&my_present_handler,
252 SCAN => \&my_scan_handler,
253 FETCH => \&my_fetch_handler);
255 After the custom event handles are declared, the server is launched
256 by means of the method
258 $z->launch_server("MyServer.pl", @ARGV);
260 Notice, the first argument should be the name of your server
261 script (for logging purposes), while the rest of the arguments
262 are documented in the YAZ toolkit manual: The section on
263 application invocation: <http://www.indexdata.dk/yaz/yaz-7.php>
267 The init handler is called whenever a Z39.50 client is attempting
268 to logon to the server. The exchange of parameters between the
269 server and the handler is carried out via an anonymous hash reached
274 The argument hash passed to the init handler has the form
277 ## Response parameters:
279 IMP_NAME => "", ## Z39.50 Implementation name
280 IMP_VER => "", ## Z39.50 Implementation version
281 ERR_CODE => 0, ## Error code, cnf. Z39.50 manual
282 USER => "xxx" ## If Z39.50 authentication is used,
283 ## this member contains user name
284 PASS => "yyy" ## Under same conditions, this member
285 ## contains the password in clear text
286 HANDLE => undef ## Handler of Perl data structure
289 The HANDLE member can be used to store any scalar value which will then
290 be provided as input to all subsequent calls (ie. for searching, record
291 retrieval, etc.). A common use of the handle is to store a reference to
292 a hash which may then be used to store session-specific parameters.
293 If you have any session-specific information (such as a list of
294 result sets or a handle to a back-end search engine of some sort),
295 it is always best to store them in a private session structure -
296 rather than leaving them in global variables in your script.
298 The Implementation name and version are only really used by Z39.50
299 client developers to see what kind of server they're dealing with.
300 Filling these in is optional.
302 The ERR_CODE should be left at 0 (the default value) if you wish to
303 accept the connection. Any other value is interpreted as a failure
304 and the client will be shown the door.
306 =head2 Search handler
308 Similarly, the search handler is called with a reference to an anony-
309 mous hash. The structure is the following:
312 ## Request parameters:
314 HANDLE => ref, ## Your session reference.
315 SETNAME => "id", ## ID of the result set
316 REPL_SET => 0, ## Replace set if already existing?
317 DATABASES => ["xxx"], ## Reference to a list of data-
319 QUERY => "query", ## The query expression
320 RPN => $obj, ## Reference to a Net::Z3950::APDU::Query
322 ## Response parameters:
324 ERR_CODE => 0, ## Error code (0=Succesful search)
325 ERR_STR => "", ## Error string
326 HITS => 0 ## Number of matches
329 Note that a search which finds 0 hits is considered successful in
330 Z39.50 terms - you should only set the ERR_CODE to a non-zero value
331 if there was a problem processing the request. The Z39.50 standard
332 provides a comprehensive list of standard diagnostic codes, and you
333 should use these whenever possible.
335 The QUERY is a tree-structure of terms combined by operators, the
336 terms being qualified by lists of attributes. The query is presented
337 to the search function in the Prefix Query Format (PQF) which is
338 used in many applications based on the YAZ toolkit. The full grammar
339 is described in the YAZ manual.
341 The following are all examples of valid queries in the PQF.
347 @or "dylan" "zimmerman"
351 @or @and bob dylan @set Result-1
353 @and @attr 1=1 "bob dylan" @attr 1=4 "slow train coming"
355 @attrset @attr 4=1 @attr 1=4 "self portrait"
357 You will need to write a recursive function or something similar to
358 parse incoming query expressions, and this is usually where a lot of
359 the work in writing a database-backend happens. Fortunately, you don't
360 need to support anymore functionality than you want to. For instance,
361 it is perfectly legal to not accept boolean operators, but you SHOULD
362 try to return good error codes if you run into something you can't or
365 A more convenient alternative to the QUERY member may be the RPN
366 member, which is a reference to a Net::Z3950::APDU::Query object
367 representing the RPN query tree. The structure of that object is
368 supposed to be self-documenting, but here's a brief summary of what
375 C<Net::Z3950::APDU::Query> is a hash with two fields:
381 =item C<attributeSet>
383 Optional. If present, it is a reference to a
384 C<Net::Z3950::APDU::OID>. This is a string of dot-separated integers
385 representing the OID of the query's top-level attribute set.
389 Mandatory: a refererence to the RPN tree itself.
395 Each node of the tree is an object of one of the following types:
401 =item C<Net::Z3950::RPN::And>
403 =item C<Net::Z3950::RPN::Or>
405 =item C<Net::Z3950::RPN::AndNot>
407 These three classes are all arrays of two elements, each of which is a
408 node of one of the above types.
410 =item C<Net::Z3950::RPN::Term>
412 See below for details.
416 (I guess I should make a superclass C<Net::Z3950::RPN::Node> and make
417 all of these subclasses of it. Not done that yet, but will do soon.)
425 C<Net::Z3950::RPN::Term> is a hash with two fields:
433 A string containing the search term itself.
437 A reference to a C<Net::Z3950::RPN::Attributes> object.
443 C<Net::Z3950::RPN::Attributes> is an array of references to
444 C<Net::Z3950::RPN::Attribute> objects. (Note the plural/singular
449 C<Net::Z3950::RPN::Attribute> is a hash with three elements:
455 =item C<attributeSet>
457 Optional. If present, it is dot-separated OID string, as above.
459 =item C<attributeType>
461 An integer indicating the type of the attribute - for example, under
462 the BIB-1 attribute set, type 1 indicates a ``use'' attribute, type 2
463 a ``relation'' attribute, etc.
465 =item C<attributeValue>
467 An integer indicating the value of the attribute - for example, under
468 BIB-1, if the attribute type is 1, then value 4 indictates a title
469 search and 7 indictates an ISBN search; but if the attribute type is
470 2, then value 4 indicates a ``greater than or equal'' search, and 102
471 indicates a relevance match.
477 Note that, at the moment, none of these classes have any methods at
478 all: the blessing into classes is largely just a documentation thing
479 so that, for example, if you do
481 { use Data::Dumper; print Dumper($args->{RPN}) }
483 you get something fairly human-readable. But of course, the type
484 distinction between the three different kinds of boolean node is
487 By adding your own methods to these classes (building what I call
488 ``augmented classes''), you can easily build code that walks the tree
489 of the incoming RPN. Take a look at C<samples/render-search.pl> for a
490 sample implementation of such an augmented classes technique.
493 =head2 Present handler
495 The presence of a present handler in a SimpleServer front-end is optional.
496 Each time a client wishes to retrieve records, the present service is
497 called. The present service allows the origin to request a certain number
498 of records retrieved from a given result set.
499 When the present handler is called, the front-end server should prepare a
500 result set for fetching. In practice, this means to get access to the
501 data from the backend database and store the data in a temporary fashion
502 for fast and efficient fetching. The present handler does *not* fetch
503 anything. This task is taken care of by the fetch handler, which will be
504 called the correct number of times by the YAZ library. More about this
506 If no present handler is implemented in the front-end, the YAZ toolkit
507 will take care of a minimum of preparations itself. This default present
508 handler is sufficient in many situations, where only a small amount of
509 records are expected to be retrieved. If on the other hand, large result
510 sets are likely to occur, the implementation of a reasonable present
511 handler can gain performance significantly.
513 The informations exchanged between client and present handle are:
516 ## Client/server request:
518 HANDLE => ref, ## Reference to datastructure
519 SETNAME => "id", ## Result set ID
520 START => xxx, ## Start position
521 COMP => "", ## Desired record composition
522 NUMBER => yyy, ## Number of requested records
525 ## Respons parameters:
527 HITS => zzz, ## Number of returned records
528 ERR_CODE => 0, ## Error code
529 ERR_STR => "" ## Error message
535 The fetch handler is asked to retrieve a SINGLE record from a given
536 result set (the front-end server will automatically call the fetch
537 handler as many times as required).
539 The parameters exchanged between the server and the fetch handler are
542 ## Client/server request:
544 HANDLE => ref ## Reference to data structure
545 SETNAME => "id" ## ID of the requested result set
546 OFFSET => nnn ## Record offset number
547 REQ_FORM => "n.m.k.l"## Client requested format OID
548 COMP => "xyz" ## Formatting instructions
552 RECORD => "" ## Record string
553 BASENAME => "" ## Origin of returned record
554 LAST => 0 ## Last record in set?
555 ERR_CODE => 0 ## Error code
556 ERR_STR => "" ## Error string
557 SUR_FLAG => 0 ## Surrogate diagnostic flag
558 REP_FORM => "n.m.k.l"## Provided format OID
561 The REP_FORM value has by default the REQ_FORM value but can be set to
562 something different if the handler desires. The BASENAME value should
563 contain the name of the database from where the returned record originates.
564 The ERR_CODE and ERR_STR works the same way they do in the search
565 handler. If there is an error condition, the SUR_FLAG is used to
566 indicate whether the error condition pertains to the record currently
567 being retrieved, or whether it pertains to the operation as a whole
568 (eg. the client has specified a result set which does not exist.)
570 If you need to return USMARC records, you might want to have a look at
571 the MARC module on CPAN, if you don't already have a way of generating
574 NOTE: The record offset is 1-indexed - 1 is the offset of the first
579 A full featured Z39.50 server should support scan (or in some literature
580 browse). The client specifies a starting term of the scan, and the server
581 should return an ordered list of specified length consisting of terms
582 actually occurring in the data base. Each of these terms should be close
583 to or equal to the term originally specified. The quality of scan compared
584 to simple search is a guarantee of hits. It is simply like browsing through
585 an index of a book, you always find something! The parameters exchanged are
590 HANDLE => $ref ## Reference to data structure
591 TERM => 'start', ## The start term
592 NUMBER => xx, ## Number of requested terms
593 POS => yy, ## Position of starting point
594 ## within returned list
595 STEP => 0, ## Step size
599 ERR_CODE => 0, ## Error code
600 ERR_STR => '', ## Diagnostic message
601 NUMBER => zz, ## Number of returned terms
602 STATUS => $status, ## ScanSuccess/ScanFailure
603 ENTRIES => $entries ## Referenced list of terms
606 where the term list is returned by reference in the scalar $entries, which
607 should point at a data structure of this kind,
613 { TERM => 'energy density',
616 { TERM => 'energy flow',
624 The $status flag should be assigned one of two values:
626 Net::Z3950::SimpleServer::ScanSuccess On success (default)
627 Net::Z3950::SimpleServer::ScanPartial Less terms returned than requested
629 The STEP member contains the requested number of entries in the term-list
630 between two adjacent entries in the response.
634 The argument hash recieved by the close handler has one element only:
638 HANDLE => ref ## Reference to data structure
641 What ever data structure the HANDLE value points at goes out of scope
642 after this call. If you need to close down a connection to your server
643 or something similar, this is the place to do it.
647 Anders Sønderberg (sondberg@indexdata.dk) and Sebastian Hammer
648 (quinn@indexdata.dk). Substantial contributions made by Mike Taylor
649 (mike@miketaylor.org.uk).
653 Any Perl module which is useful for accessing the database of your