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 1.11 2002-03-05 20:49:56 sondberg
30 ## Added a couple of lines of documentation.
32 ## Revision 1.10 2002/02/28 11:21:57 mike
33 ## Add RPN structure to search-handler argument hash.
35 ## Revision 1.9 2001/08/29 11:48:36 sondberg
38 ## Net::Z3950::SimpleServer::ScanSuccess
39 ## Net::Z3950::SimpleServer::ScanPartial
41 ## and a bit of documentation.
43 ## Revision 1.8 2001/08/29 10:29:51 sondberg
44 ## Added some documentation of scan.
46 ## Revision 1.7 2001/08/24 14:00:20 sondberg
47 ## Added support for scan.
49 ## Revision 1.6 2001/03/13 14:17:15 sondberg
50 ## Added support for GRS-1.
53 package Net::Z3950::SimpleServer;
56 use vars qw($VERSION @ISA @EXPORT @EXPORT_OK);
63 @ISA = qw(Exporter AutoLoader DynaLoader);
64 # Items to export into callers namespace by default. Note: do not export
65 # names by default without a very good reason. Use EXPORT_OK instead.
66 # Do not simply export all your public functions/methods/constants.
72 bootstrap Net::Z3950::SimpleServer $VERSION;
74 # Preloaded methods go here.
84 carp "SimpleServer.pm: WARNING: Multithreaded server unsupported";
88 croak "SimpleServer.pm: ERROR: Unspecified search handler" unless defined($self->{SEARCH});
89 croak "SimpleServer.pm: ERROR: Unspecified fetch handler" unless defined($self->{FETCH});
100 if (defined($self->{INIT})) {
101 set_init_handler($self->{INIT});
103 set_search_handler($self->{SEARCH});
104 set_fetch_handler($self->{FETCH});
105 if (defined($self->{CLOSE})) {
106 set_close_handler($self->{CLOSE});
108 if (defined($self->{PRESENT})) {
109 set_present_handler($self->{PRESENT});
111 if (defined($self->{SCAN})) {
112 set_scan_handler($self->{SCAN});
119 # Register packages that we will use in translated RPNs
120 package Net::Z3950::APDU::Query;
121 package Net::Z3950::APDU::OID;
122 package Net::Z3950::RPN::And;
123 package Net::Z3950::RPN::Or;
124 package Net::Z3950::RPN::AndNot;
125 package Net::Z3950::RPN::Term;
126 package Net::Z3950::RPN::Attributes;
127 package Net::Z3950::RPN::Attribute;
129 # Must revert to original package for Autoloader's benefit
130 package Net::Z3950::SimpleServer;
133 # Autoload methods go after =cut, and are processed by the autosplit program.
137 # Below is the stub of documentation for your module. You better edit it!
141 Net::Z3950::SimpleServer - Simple Perl API for building Z39.50 servers.
145 use Net::Z3950::SimpleServer;
147 sub my_search_handler {
150 my $set_id = $args->{SETNAME};
151 my @database_list = @{ $args->{DATABASES} };
152 my $query = $args->{QUERY};
154 ## Perform the query on the specified set of databases
155 ## and return the number of hits:
157 $args->{HITS} = $hits;
160 sub my_fetch_handler { # Get a record for the user
163 my $set_id = $args->{SETNAME};
165 my $record = fetch_a_record($args->{OFFSET});
167 $args->{RECORD} = $record;
168 if (number_of_hits() == $args->{OFFSET}) { ## Last record in set?
176 ## Register custom event handlers:
178 my $z = new Net::Z3950::SimpleServer( INIT => \&my_init_handler,
179 CLOSE => \&my_close_handler,
180 SEARCH => \&my_search_handler,
181 FETCH => \&my_fetch_handler);
184 $z->launch_server("ztest.pl", @ARGV);
188 The SimpleServer module is a tool for constructing Z39.50 "Information
189 Retrieval" servers in Perl. The module is easy to use, but it
190 does help to have an understanding of the Z39.50 query
191 structure and the construction of structured retrieval records.
193 Z39.50 is a network protocol for searching remote databases and
194 retrieving the results in the form of structured "records". It is widely
195 used in libraries around the world, as well as in the US Federal Government.
196 In addition, it is generally useful whenever you wish to integrate a number
197 of different database systems around a shared, asbtract data model.
199 The model of the module is simple: It implements a "generic" Z39.50
200 server, which invokes callback functions supplied by you to search
201 for content in your database. You can use any tools available in
202 Perl to supply the content, including modules like DBI and
205 The server will take care of managing the network connections for
206 you, and it will spawn a new process (or thread, in some
207 environments) whenever a new connection is received.
209 The programmer can specify subroutines to take care of the following type
215 - Fetching of records
216 - Scan request (browsing)
217 - Closing down connection
219 Note that only the Search and Fetch handler functions are required.
220 The module can supply default responses to the other on its own.
222 After the launching of the server, all control is given away from
223 the Perl script to the server. The server calls the registered
224 subroutines to field incoming requests from Z39.50 clients.
226 A reference to an anonymous hash is passed to each handle. Some of
227 the entries of these hashes are to be considered input and others
230 The Perl programmer specifies the event handles for the server by
231 means of the the SimpleServer object constructor
233 my $z = new Net::Z3950::SimpleServer(
234 INIT => \&my_init_handler,
235 CLOSE => \&my_close_handler,
236 SEARCH => \&my_search_handler,
237 PRESENT => \&my_present_handler,
238 SCAN => \&my_scan_handler,
239 FETCH => \&my_fetch_handler);
241 After the custom event handles are declared, the server is launched
242 by means of the method
244 $z->launch_server("MyServer.pl", @ARGV);
246 Notice, the first argument should be the name of your server
247 script (for logging purposes), while the rest of the arguments
248 are documented in the YAZ toolkit manual: The section on
249 application invocation: <http://www.indexdata.dk/yaz/yaz-7.php>
253 The init handler is called whenever a Z39.50 client is attempting
254 to logon to the server. The exchange of parameters between the
255 server and the handler is carried out via an anonymous hash reached
260 The argument hash passed to the init handler has the form
263 ## Response parameters:
265 IMP_NAME => "", ## Z39.50 Implementation name
266 IMP_VER => "", ## Z39.50 Implementation version
267 ERR_CODE => 0, ## Error code, cnf. Z39.50 manual
268 HANDLE => undef ## Handler of Perl data structure
271 The HANDLE member can be used to store any scalar value which will then
272 be provided as input to all subsequent calls (ie. for searching, record
273 retrieval, etc.). A common use of the handle is to store a reference to
274 a hash which may then be used to store session-specific parameters.
275 If you have any session-specific information (such as a list of
276 result sets or a handle to a back-end search engine of some sort),
277 it is always best to store them in a private session structure -
278 rather than leaving them in global variables in your script.
280 The Implementation name and version are only really used by Z39.50
281 client developers to see what kind of server they're dealing with.
282 Filling these in is optional.
284 The ERR_CODE should be left at 0 (the default value) if you wish to
285 accept the connection. Any other value is interpreted as a failure
286 and the client will be shown the door.
288 =head2 Search handler
290 Similarly, the search handler is called with a reference to an anony-
291 mous hash. The structure is the following:
294 ## Request parameters:
296 HANDLE => ref, ## Your session reference.
297 SETNAME => "id", ## ID of the result set
298 REPL_SET => 0, ## Replace set if already existing?
299 DATABASES => ["xxx"], ## Reference to a list of data-
301 QUERY => "query", ## The query expression
302 RPN => $obj, ## Blessed reference int the package
303 ## Net::Z3950::APDU::Query
305 ## Response parameters:
307 ERR_CODE => 0, ## Error code (0=Succesful search)
308 ERR_STR => "", ## Error string
309 HITS => 0 ## Number of matches
312 Note that a search which finds 0 hits is considered successful in
313 Z39.50 terms - you should only set the ERR_CODE to a non-zero value
314 if there was a problem processing the request. The Z39.50 standard
315 provides a comprehensive list of standard diagnostic codes, and you
316 should use these whenever possible.
318 The QUERY is a tree-structure of terms combined by operators, the
319 terms being qualified by lists of attributes. The query is presented
320 to the search function in the Prefix Query Format (PQF) which is
321 used in many applications based on the YAZ toolkit. The full grammar
322 is described in the YAZ manual.
324 The following are all examples of valid queries in the PQF.
330 @or "dylan" "zimmerman"
334 @or @and bob dylan @set Result-1
336 @and @attr 1=1 "bob dylan" @attr 1=4 "slow train coming"
338 @attrset @attr 4=1 @attr 1=4 "self portrait"
340 You will need to write a recursive function or something similar to
341 parse incoming query expressions, and this is usually where a lot of
342 the work in writing a database-backend happens. Fortunately, you don't
343 need to support anymore functionality than you want to. For instance,
344 it is perfectly legal to not accept boolean operators, but you SHOULD
345 try to return good error codes if you run into something you can't or
348 The RPN member is a blessed reference into the package Net::Z3950::APDU::Query.
349 By means of an augmented type of coding, you can easily construct a
350 parser of the incoming RPN. Take a look at samples/render-search.pl for
351 a sample implementation of such an augmented parser technique.
353 =head2 Present handler
355 The presence of a present handler in a SimpleServer front-end is optional.
356 Each time a client wishes to retrieve records, the present service is
357 called. The present service allows the origin to request a certain number
358 of records retrieved from a given result set.
359 When the present handler is called, the front-end server should prepare a
360 result set for fetching. In practice, this means to get access to the
361 data from the backend database and store the data in a temporary fashion
362 for fast and efficient fetching. The present handler does *not* fetch
363 anything. This task is taken care of by the fetch handler, which will be
364 called the correct number of times by the YAZ library. More about this
366 If no present handler is implemented in the front-end, the YAZ toolkit
367 will take care of a minimum of preparations itself. This default present
368 handler is sufficient in many situations, where only a small amount of
369 records are expected to be retrieved. If on the other hand, large result
370 sets are likely to occur, the implementation of a reasonable present
371 handler can gain performance significantly.
373 The informations exchanged between client and present handle are:
376 ## Client/server request:
378 HANDLE => ref, ## Reference to datastructure
379 SETNAME => "id", ## Result set ID
380 START => xxx, ## Start position
381 COMP => "", ## Desired record composition
382 NUMBER => yyy, ## Number of requested records
385 ## Respons parameters:
387 HITS => zzz, ## Number of returned records
388 ERR_CODE => 0, ## Error code
389 ERR_STR => "" ## Error message
395 The fetch handler is asked to retrieve a SINGLE record from a given
396 result set (the front-end server will automatically call the fetch
397 handler as many times as required).
399 The parameters exchanged between the server and the fetch handler are
402 ## Client/server request:
404 HANDLE => ref ## Reference to data structure
405 SETNAME => "id" ## ID of the requested result set
406 OFFSET => nnn ## Record offset number
407 REQ_FORM => "n.m.k.l"## Client requested format OID
408 COMP => "xyz" ## Formatting instructions
412 RECORD => "" ## Record string
413 BASENAME => "" ## Origin of returned record
414 LAST => 0 ## Last record in set?
415 ERR_CODE => 0 ## Error code
416 ERR_STR => "" ## Error string
417 SUR_FLAG => 0 ## Surrogate diagnostic flag
418 REP_FORM => "n.m.k.l"## Provided format OID
421 The REP_FORM value has by default the REQ_FORM value but can be set to
422 something different if the handler desires. The BASENAME value should
423 contain the name of the database from where the returned record originates.
424 The ERR_CODE and ERR_STR works the same way they do in the search
425 handler. If there is an error condition, the SUR_FLAG is used to
426 indicate whether the error condition pertains to the record currently
427 being retrieved, or whether it pertains to the operation as a whole
428 (eg. the client has specified a result set which does not exist.)
430 If you need to return USMARC records, you might want to have a look at
431 the MARC module on CPAN, if you don't already have a way of generating
434 NOTE: The record offset is 1-indexed - 1 is the offset of the first
439 A full featured Z39.50 server should support scan (or in some literature
440 browse). The client specifies a starting term of the scan, and the server
441 should return an ordered list of specified length consisting of terms
442 actually occurring in the data base. Each of these terms should be close
443 to or equal to the term originally specified. The quality of scan compared
444 to simple search is a guarantee of hits. It is simply like browsing through
445 an index of a book, you always find something! The parameters exchanged are
450 HANDLE => $ref ## Reference to data structure
451 TERM => 'start', ## The start term
452 NUMBER => xx, ## Number of requested terms
453 POS => yy, ## Position of starting point
454 ## within returned list
455 STEP => 0, ## Step size
459 ERR_CODE => 0, ## Error code
460 ERR_STR => '', ## Diagnostic message
461 NUMBER => zz, ## Number of returned terms
462 STATUS => $status, ## ScanSuccess/ScanFailure
463 ENTRIES => $entries ## Referenced list of terms
466 where the term list is returned by reference in the scalar $entries, which
467 should point at a data structure of this kind,
473 { TERM => 'energy density',
476 { TERM => 'energy flow',
484 The $status flag should be assigned one of two values:
486 Net::Z3950::SimpleServer::ScanSuccess On success (default)
487 Net::Z3950::SimpleServer::ScanPartial Less terms returned than requested
489 The STEP member contains the requested number of entries in the term-list
490 between two adjacent entries in the response.
494 The argument hash recieved by the close handler has one element only:
498 HANDLE => ref ## Reference to data structure
501 What ever data structure the HANDLE value points at goes out of scope
502 after this call. If you need to close down a connection to your server
503 or something similar, this is the place to do it.
507 Anders Sønderberg (sondberg@indexdata.dk) and Sebastian Hammer
508 (quinn@indexdata.dk). Substantial contributions made by Mike Taylor (mike@tecc.co.uk).
514 Any Perl module which is useful for accessing the database of your