2 ## Copyright (c) 2000-2004, 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 ## $Id: SimpleServer.pm,v 1.21 2004-06-04 09:57:00 sondberg Exp $
30 package Net::Z3950::SimpleServer;
33 use vars qw($VERSION @ISA @EXPORT @EXPORT_OK);
40 @ISA = qw(Exporter AutoLoader DynaLoader);
44 bootstrap Net::Z3950::SimpleServer $VERSION;
46 # Preloaded methods go here.
56 carp "SimpleServer.pm: WARNING: Multithreaded server unsupported";
60 croak "SimpleServer.pm: ERROR: Unspecified search handler" unless defined($self->{SEARCH});
61 croak "SimpleServer.pm: ERROR: Unspecified fetch handler" unless defined($self->{FETCH});
72 if (defined($self->{INIT})) {
73 set_init_handler($self->{INIT});
75 set_search_handler($self->{SEARCH});
76 set_fetch_handler($self->{FETCH});
77 if (defined($self->{CLOSE})) {
78 set_close_handler($self->{CLOSE});
80 if (defined($self->{PRESENT})) {
81 set_present_handler($self->{PRESENT});
83 if (defined($self->{SCAN})) {
84 set_scan_handler($self->{SCAN});
91 # Register packages that we will use in translated RPNs
92 package Net::Z3950::APDU::Query;
93 package Net::Z3950::APDU::OID;
94 package Net::Z3950::RPN::And;
95 package Net::Z3950::RPN::Or;
96 package Net::Z3950::RPN::AndNot;
97 package Net::Z3950::RPN::Term;
98 package Net::Z3950::RPN::Attributes;
99 package Net::Z3950::RPN::Attribute;
101 # Must revert to original package for Autoloader's benefit
102 package Net::Z3950::SimpleServer;
105 # Autoload methods go after =cut, and are processed by the autosplit program.
109 # Below is the stub of documentation for your module. You better edit it!
113 Net::Z3950::SimpleServer - Simple Perl API for building Z39.50 servers.
117 use Net::Z3950::SimpleServer;
119 sub my_search_handler {
122 my $set_id = $args->{SETNAME};
123 my @database_list = @{ $args->{DATABASES} };
124 my $query = $args->{QUERY};
126 ## Perform the query on the specified set of databases
127 ## and return the number of hits:
129 $args->{HITS} = $hits;
132 sub my_fetch_handler { # Get a record for the user
135 my $set_id = $args->{SETNAME};
137 my $record = fetch_a_record($args->{OFFSET});
139 $args->{RECORD} = $record;
140 if (number_of_hits() == $args->{OFFSET}) { ## Last record in set?
148 ## Register custom event handlers:
150 my $z = new Net::Z3950::SimpleServer( INIT => \&my_init_handler,
151 CLOSE => \&my_close_handler,
152 SEARCH => \&my_search_handler,
153 FETCH => \&my_fetch_handler);
156 $z->launch_server("ztest.pl", @ARGV);
160 The SimpleServer module is a tool for constructing Z39.50 "Information
161 Retrieval" servers in Perl. The module is easy to use, but it
162 does help to have an understanding of the Z39.50 query
163 structure and the construction of structured retrieval records.
165 Z39.50 is a network protocol for searching remote databases and
166 retrieving the results in the form of structured "records". It is widely
167 used in libraries around the world, as well as in the US Federal Government.
168 In addition, it is generally useful whenever you wish to integrate a number
169 of different database systems around a shared, asbtract data model.
171 The model of the module is simple: It implements a "generic" Z39.50
172 server, which invokes callback functions supplied by you to search
173 for content in your database. You can use any tools available in
174 Perl to supply the content, including modules like DBI and
177 The server will take care of managing the network connections for
178 you, and it will spawn a new process (or thread, in some
179 environments) whenever a new connection is received.
181 The programmer can specify subroutines to take care of the following type
187 - Fetching of records
188 - Scan request (browsing)
189 - Closing down connection
191 Note that only the Search and Fetch handler functions are required.
192 The module can supply default responses to the other on its own.
194 After the launching of the server, all control is given away from
195 the Perl script to the server. The server calls the registered
196 subroutines to field incoming requests from Z39.50 clients.
198 A reference to an anonymous hash is passed to each handler. Some of
199 the entries of these hashes are to be considered input and others
202 The Perl programmer specifies the event handlers for the server by
203 means of the SimpleServer object constructor
205 my $z = new Net::Z3950::SimpleServer(
206 INIT => \&my_init_handler,
207 CLOSE => \&my_close_handler,
208 SEARCH => \&my_search_handler,
209 PRESENT => \&my_present_handler,
210 SCAN => \&my_scan_handler,
211 FETCH => \&my_fetch_handler);
213 If you want your SimpleServer to start a thread (threaded mode) to
214 handle each incoming Z39.50 request instead of forking a process
215 (forking mode), you need to register the handlers by symbol rather
216 than by code reference. Thus, in threaded mode, you will need to
217 register your handlers this way:
219 my $z = new Net::Z3950::SimpleServer(
220 INIT => "my_package::my_init_handler",
221 CLOSE => "my_package::my_close_handler",
225 where my_package is the Perl package in which your handler is
228 After the custom event handlers are declared, the server is launched
229 by means of the method
231 $z->launch_server("MyServer.pl", @ARGV);
233 Notice, the first argument should be the name of your server
234 script (for logging purposes), while the rest of the arguments
235 are documented in the YAZ toolkit manual: The section on
236 application invocation: <http://www.indexdata.dk/yaz/yaz-7.php>
238 In particular, you need to use the -T switch to start your SimpleServer
243 The init handler is called whenever a Z39.50 client is attempting
244 to logon to the server. The exchange of parameters between the
245 server and the handler is carried out via an anonymous hash reached
250 The argument hash passed to the init handler has the form
253 ## Response parameters:
255 IMP_ID => "", ## Z39.50 Implementation ID
256 IMP_NAME => "", ## Z39.50 Implementation name
257 IMP_VER => "", ## Z39.50 Implementation version
258 ERR_CODE => 0, ## Error code, cnf. Z39.50 manual
259 ERR_STR => "", ## Error string (additional info.)
260 USER => "xxx" ## If Z39.50 authentication is used,
261 ## this member contains user name
262 PASS => "yyy" ## Under same conditions, this member
263 ## contains the password in clear text
264 HANDLE => undef ## Handler of Perl data structure
267 The HANDLE member can be used to store any scalar value which will then
268 be provided as input to all subsequent calls (ie. for searching, record
269 retrieval, etc.). A common use of the handle is to store a reference to
270 a hash which may then be used to store session-specific parameters.
271 If you have any session-specific information (such as a list of
272 result sets or a handle to a back-end search engine of some sort),
273 it is always best to store them in a private session structure -
274 rather than leaving them in global variables in your script.
276 The Implementation ID, name and version are only really used by Z39.50
277 client developers to see what kind of server they're dealing with.
278 Filling these in is optional.
280 The ERR_CODE should be left at 0 (the default value) if you wish to
281 accept the connection. Any other value is interpreted as a failure
282 and the client will be shown the door, with the code and the
283 associated additional information, ERR_STR returned.
285 =head2 Search handler
287 Similarly, the search handler is called with a reference to an anony-
288 mous hash. The structure is the following:
291 ## Request parameters:
293 HANDLE => ref, ## Your session reference.
294 SETNAME => "id", ## ID of the result set
295 REPL_SET => 0, ## Replace set if already existing?
296 DATABASES => ["xxx"], ## Reference to a list of data-
298 QUERY => "query", ## The query expression
299 RPN => $obj, ## Reference to a Net::Z3950::APDU::Query
301 ## Response parameters:
303 ERR_CODE => 0, ## Error code (0=Succesful search)
304 ERR_STR => "", ## Error string
305 HITS => 0 ## Number of matches
308 Note that a search which finds 0 hits is considered successful in
309 Z39.50 terms - you should only set the ERR_CODE to a non-zero value
310 if there was a problem processing the request. The Z39.50 standard
311 provides a comprehensive list of standard diagnostic codes, and you
312 should use these whenever possible.
314 The QUERY is a tree-structure of terms combined by operators, the
315 terms being qualified by lists of attributes. The query is presented
316 to the search function in the Prefix Query Format (PQF) which is
317 used in many applications based on the YAZ toolkit. The full grammar
318 is described in the YAZ manual.
320 The following are all examples of valid queries in the PQF.
326 @or "dylan" "zimmerman"
330 @or @and bob dylan @set Result-1
332 @and @attr 1=1 "bob dylan" @attr 1=4 "slow train coming"
334 @attrset @attr 4=1 @attr 1=4 "self portrait"
336 You will need to write a recursive function or something similar to
337 parse incoming query expressions, and this is usually where a lot of
338 the work in writing a database-backend happens. Fortunately, you don't
339 need to support anymore functionality than you want to. For instance,
340 it is perfectly legal to not accept boolean operators, but you SHOULD
341 try to return good error codes if you run into something you can't or
344 A more convenient alternative to the QUERY member may be the RPN
345 member, which is a reference to a Net::Z3950::APDU::Query object
346 representing the RPN query tree. The structure of that object is
347 supposed to be self-documenting, but here's a brief summary of what
354 C<Net::Z3950::APDU::Query> is a hash with two fields:
360 =item C<attributeSet>
362 Optional. If present, it is a reference to a
363 C<Net::Z3950::APDU::OID>. This is a string of dot-separated integers
364 representing the OID of the query's top-level attribute set.
368 Mandatory: a refererence to the RPN tree itself.
374 Each node of the tree is an object of one of the following types:
380 =item C<Net::Z3950::RPN::And>
382 =item C<Net::Z3950::RPN::Or>
384 =item C<Net::Z3950::RPN::AndNot>
386 These three classes are all arrays of two elements, each of which is a
387 node of one of the above types.
389 =item C<Net::Z3950::RPN::Term>
391 See below for details.
395 (I guess I should make a superclass C<Net::Z3950::RPN::Node> and make
396 all of these subclasses of it. Not done that yet, but will do soon.)
404 C<Net::Z3950::RPN::Term> is a hash with two fields:
412 A string containing the search term itself.
416 A reference to a C<Net::Z3950::RPN::Attributes> object.
422 C<Net::Z3950::RPN::Attributes> is an array of references to
423 C<Net::Z3950::RPN::Attribute> objects. (Note the plural/singular
428 C<Net::Z3950::RPN::Attribute> is a hash with three elements:
434 =item C<attributeSet>
436 Optional. If present, it is dot-separated OID string, as above.
438 =item C<attributeType>
440 An integer indicating the type of the attribute - for example, under
441 the BIB-1 attribute set, type 1 indicates a ``use'' attribute, type 2
442 a ``relation'' attribute, etc.
444 =item C<attributeValue>
446 An integer indicating the value of the attribute - for example, under
447 BIB-1, if the attribute type is 1, then value 4 indictates a title
448 search and 7 indictates an ISBN search; but if the attribute type is
449 2, then value 4 indicates a ``greater than or equal'' search, and 102
450 indicates a relevance match.
456 Note that, at the moment, none of these classes have any methods at
457 all: the blessing into classes is largely just a documentation thing
458 so that, for example, if you do
460 { use Data::Dumper; print Dumper($args->{RPN}) }
462 you get something fairly human-readable. But of course, the type
463 distinction between the three different kinds of boolean node is
466 By adding your own methods to these classes (building what I call
467 ``augmented classes''), you can easily build code that walks the tree
468 of the incoming RPN. Take a look at C<samples/render-search.pl> for a
469 sample implementation of such an augmented classes technique.
472 =head2 Present handler
474 The presence of a present handler in a SimpleServer front-end is optional.
475 Each time a client wishes to retrieve records, the present service is
476 called. The present service allows the origin to request a certain number
477 of records retrieved from a given result set.
478 When the present handler is called, the front-end server should prepare a
479 result set for fetching. In practice, this means to get access to the
480 data from the backend database and store the data in a temporary fashion
481 for fast and efficient fetching. The present handler does *not* fetch
482 anything. This task is taken care of by the fetch handler, which will be
483 called the correct number of times by the YAZ library. More about this
485 If no present handler is implemented in the front-end, the YAZ toolkit
486 will take care of a minimum of preparations itself. This default present
487 handler is sufficient in many situations, where only a small amount of
488 records are expected to be retrieved. If on the other hand, large result
489 sets are likely to occur, the implementation of a reasonable present
490 handler can gain performance significantly.
492 The informations exchanged between client and present handle are:
495 ## Client/server request:
497 HANDLE => ref, ## Reference to datastructure
498 SETNAME => "id", ## Result set ID
499 START => xxx, ## Start position
500 COMP => "", ## Desired record composition
501 NUMBER => yyy, ## Number of requested records
504 ## Respons parameters:
506 HITS => zzz, ## Number of returned records
507 ERR_CODE => 0, ## Error code
508 ERR_STR => "" ## Error message
514 The fetch handler is asked to retrieve a SINGLE record from a given
515 result set (the front-end server will automatically call the fetch
516 handler as many times as required).
518 The parameters exchanged between the server and the fetch handler are
521 ## Client/server request:
523 HANDLE => ref ## Reference to data structure
524 SETNAME => "id" ## ID of the requested result set
525 OFFSET => nnn ## Record offset number
526 REQ_FORM => "n.m.k.l"## Client requested format OID
527 COMP => "xyz" ## Formatting instructions
531 RECORD => "" ## Record string
532 BASENAME => "" ## Origin of returned record
533 LAST => 0 ## Last record in set?
534 ERR_CODE => 0 ## Error code
535 ERR_STR => "" ## Error string
536 SUR_FLAG => 0 ## Surrogate diagnostic flag
537 REP_FORM => "n.m.k.l"## Provided format OID
540 The REP_FORM value has by default the REQ_FORM value but can be set to
541 something different if the handler desires. The BASENAME value should
542 contain the name of the database from where the returned record originates.
543 The ERR_CODE and ERR_STR works the same way they do in the search
544 handler. If there is an error condition, the SUR_FLAG is used to
545 indicate whether the error condition pertains to the record currently
546 being retrieved, or whether it pertains to the operation as a whole
547 (eg. the client has specified a result set which does not exist.)
549 If you need to return USMARC records, you might want to have a look at
550 the MARC module on CPAN, if you don't already have a way of generating
553 NOTE: The record offset is 1-indexed - 1 is the offset of the first
558 A full featured Z39.50 server should support scan (or in some literature
559 browse). The client specifies a starting term of the scan, and the server
560 should return an ordered list of specified length consisting of terms
561 actually occurring in the data base. Each of these terms should be close
562 to or equal to the term originally specified. The quality of scan compared
563 to simple search is a guarantee of hits. It is simply like browsing through
564 an index of a book, you always find something! The parameters exchanged are
569 HANDLE => $ref ## Reference to data structure
570 TERM => 'start', ## The start term
571 NUMBER => xx, ## Number of requested terms
572 POS => yy, ## Position of starting point
573 ## within returned list
574 STEP => 0, ## Step size
578 ERR_CODE => 0, ## Error code
579 ERR_STR => '', ## Diagnostic message
580 NUMBER => zz, ## Number of returned terms
581 STATUS => $status, ## ScanSuccess/ScanFailure
582 ENTRIES => $entries ## Referenced list of terms
585 where the term list is returned by reference in the scalar $entries, which
586 should point at a data structure of this kind,
592 { TERM => 'energy density',
595 { TERM => 'energy flow',
603 The $status flag should be assigned one of two values:
605 Net::Z3950::SimpleServer::ScanSuccess On success (default)
606 Net::Z3950::SimpleServer::ScanPartial Less terms returned than requested
608 The STEP member contains the requested number of entries in the term-list
609 between two adjacent entries in the response.
613 The argument hash recieved by the close handler has one element only:
617 HANDLE => ref ## Reference to data structure
620 What ever data structure the HANDLE value points at goes out of scope
621 after this call. If you need to close down a connection to your server
622 or something similar, this is the place to do it.
626 Anders Sønderberg (sondberg@indexdata.dk) and Sebastian Hammer
627 (quinn@indexdata.dk). Substantial contributions made by Mike Taylor
628 (mike@miketaylor.org.uk).
632 Any Perl module which is useful for accessing the database of your