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 1.9 2001-08-29 11:48:36 sondberg
32 ## Net::Z3950::SimpleServer::ScanSuccess
33 ## Net::Z3950::SimpleServer::ScanPartial
35 ## and a bit of documentation.
37 ## Revision 1.8 2001/08/29 10:29:51 sondberg
38 ## Added some documentation of scan.
40 ## Revision 1.7 2001/08/24 14:00:20 sondberg
41 ## Added support for scan.
43 ## Revision 1.6 2001/03/13 14:17:15 sondberg
44 ## Added support for GRS-1.
47 package Net::Z3950::SimpleServer;
50 use vars qw($VERSION @ISA @EXPORT @EXPORT_OK);
57 @ISA = qw(Exporter AutoLoader DynaLoader);
58 # Items to export into callers namespace by default. Note: do not export
59 # names by default without a very good reason. Use EXPORT_OK instead.
60 # Do not simply export all your public functions/methods/constants.
66 bootstrap Net::Z3950::SimpleServer $VERSION;
68 # Preloaded methods go here.
78 carp "SimpleServer.pm: WARNING: Multithreaded server unsupported";
82 croak "SimpleServer.pm: ERROR: Unspecified search handler" unless defined($self->{SEARCH});
83 croak "SimpleServer.pm: ERROR: Unspecified fetch handler" unless defined($self->{FETCH});
94 if (defined($self->{INIT})) {
95 set_init_handler($self->{INIT});
97 set_search_handler($self->{SEARCH});
98 set_fetch_handler($self->{FETCH});
99 if (defined($self->{CLOSE})) {
100 set_close_handler($self->{CLOSE});
102 if (defined($self->{PRESENT})) {
103 set_present_handler($self->{PRESENT});
105 if (defined($self->{SCAN})) {
106 set_scan_handler($self->{SCAN});
113 # Autoload methods go after =cut, and are processed by the autosplit program.
117 # Below is the stub of documentation for your module. You better edit it!
121 Net::Z3950::SimpleServer - Simple Perl API for building Z39.50 servers.
125 use Net::Z3950::SimpleServer;
127 sub my_search_handler {
130 my $set_id = $args->{SETNAME};
131 my @database_list = @{ $args->{DATABASES} };
132 my $query = $args->{QUERY};
134 ## Perform the query on the specified set of databases
135 ## and return the number of hits:
137 $args->{HITS} = $hits;
140 sub my_fetch_handler { # Get a record for the user
143 my $set_id = $args->{SETNAME};
145 my $record = fetch_a_record($args->{OFFSET});
147 $args->{RECORD} = $record;
148 if (number_of_hits() == $args->{OFFSET}) { ## Last record in set?
156 ## Register custom event handlers:
158 my $z = new Net::Z3950::SimpleServer( INIT => \&my_init_handler,
159 CLOSE => \&my_close_handler,
160 SEARCH => \&my_search_handler,
161 FETCH => \&my_fetch_handler);
164 $z->launch_server("ztest.pl", @ARGV);
168 The SimpleServer module is a tool for constructing Z39.50 "Information
169 Retrieval" servers in Perl. The module is easy to use, but it
170 does help to have an understanding of the Z39.50 query
171 structure and the construction of structured retrieval records.
173 Z39.50 is a network protocol for searching remote databases and
174 retrieving the results in the form of structured "records". It is widely
175 used in libraries around the world, as well as in the US Federal Government.
176 In addition, it is generally useful whenever you wish to integrate a number
177 of different database systems around a shared, asbtract data model.
179 The model of the module is simple: It implements a "generic" Z39.50
180 server, which invokes callback functions supplied by you to search
181 for content in your database. You can use any tools available in
182 Perl to supply the content, including modules like DBI and
185 The server will take care of managing the network connections for
186 you, and it will spawn a new process (or thread, in some
187 environments) whenever a new connection is received.
189 The programmer can specify subroutines to take care of the following type
195 - Fetching of records
196 - Scan request (browsing)
197 - Closing down connection
199 Note that only the Search and Fetch handler functions are required.
200 The module can supply default responses to the other on its own.
202 After the launching of the server, all control is given away from
203 the Perl script to the server. The server calls the registered
204 subroutines to field incoming requests from Z39.50 clients.
206 A reference to an anonymous hash is passed to each handle. Some of
207 the entries of these hashes are to be considered input and others
210 The Perl programmer specifies the event handles for the server by
211 means of the the SimpleServer object constructor
213 my $z = new Net::Z3950::SimpleServer(
214 INIT => \&my_init_handler,
215 CLOSE => \&my_close_handler,
216 SEARCH => \&my_search_handler,
217 PRESENT => \&my_present_handler,
218 SCAN => \&my_scan_handler,
219 FETCH => \&my_fetch_handler);
221 After the custom event handles are declared, the server is launched
222 by means of the method
224 $z->launch_server("MyServer.pl", @ARGV);
226 Notice, the first argument should be the name of your server
227 script (for logging purposes), while the rest of the arguments
228 are documented in the YAZ toolkit manual: The section on
229 application invocation: <http://www.indexdata.dk/yaz/yaz-7.php>
233 The init handler is called whenever a Z39.50 client is attempting
234 to logon to the server. The exchange of parameters between the
235 server and the handler is carried out via an anonymous hash reached
240 The argument hash passed to the init handler has the form
243 ## Response parameters:
245 IMP_NAME => "", ## Z39.50 Implementation name
246 IMP_VER => "", ## Z39.50 Implementation version
247 ERR_CODE => 0, ## Error code, cnf. Z39.50 manual
248 HANDLE => undef ## Handler of Perl data structure
251 The HANDLE member can be used to store any scalar value which will then
252 be provided as input to all subsequent calls (ie. for searching, record
253 retrieval, etc.). A common use of the handle is to store a reference to
254 a hash which may then be used to store session-specific parameters.
255 If you have any session-specific information (such as a list of
256 result sets or a handle to a back-end search engine of some sort),
257 it is always best to store them in a private session structure -
258 rather than leaving them in global variables in your script.
260 The Implementation name and version are only really used by Z39.50
261 client developers to see what kind of server they're dealing with.
262 Filling these in is optional.
264 The ERR_CODE should be left at 0 (the default value) if you wish to
265 accept the connection. Any other value is interpreted as a failure
266 and the client will be shown the door.
268 =head2 Search handler
270 Similarly, the search handler is called with a reference to an anony-
271 mous hash. The structure is the following:
274 ## Request parameters:
276 HANDLE => ref, ## Your session reference.
277 SETNAME => "id", ## ID of the result set
278 REPL_SET => 0, ## Replace set if already existing?
279 DATABASES => ["xxx"], ## Reference to a list of data-
281 QUERY => "query", ## The query expression
283 ## Response parameters:
285 ERR_CODE => 0, ## Error code (0=Succesful search)
286 ERR_STR => "", ## Error string
287 HITS => 0 ## Number of matches
290 Note that a search which finds 0 hits is considered successful in
291 Z39.50 terms - you should only set the ERR_CODE to a non-zero value
292 if there was a problem processing the request. The Z39.50 standard
293 provides a comprehensive list of standard diagnostic codes, and you
294 should use these whenever possible.
296 The QUERY is a tree-structure of terms combined by operators, the
297 terms being qualified by lists of attributes. The query is presented
298 to the search function in the Prefix Query Format (PQF) which is
299 used in many applications based on the YAZ toolkit. The full grammar
300 is described in the YAZ manual.
302 The following are all examples of valid queries in the PQF.
308 @or "dylan" "zimmerman"
312 @or @and bob dylan @set Result-1
314 @and @attr 1=1 "bob dylan" @attr 1=4 "slow train coming"
316 @attrset @attr 4=1 @attr 1=4 "self portrait"
318 You will need to write a recursive function or something similar to
319 parse incoming query expressions, and this is usually where a lot of
320 the work in writing a database-backend happens. Fortunately, you don't
321 need to support anymore functionality than you want to. For instance,
322 it is perfectly legal to not accept boolean operators, but you SHOULD
323 try to return good error codes if you run into something you can't or
326 =head2 Present handler
328 The presence of a present handler in a SimpleServer front-end is optional.
329 Each time a client wishes to retrieve records, the present service is
330 called. The present service allows the origin to request a certain number
331 of records retrieved from a given result set.
332 When the present handler is called, the front-end server should prepare a
333 result set for fetching. In practice, this means to get access to the
334 data from the backend database and store the data in a temporary fashion
335 for fast and efficient fetching. The present handler does *not* fetch
336 anything. This task is taken care of by the fetch handler, which will be
337 called the correct number of times by the YAZ library. More about this
339 If no present handler is implemented in the front-end, the YAZ toolkit
340 will take care of a minimum of preparations itself. This default present
341 handler is sufficient in many situations, where only a small amount of
342 records are expected to be retrieved. If on the other hand, large result
343 sets are likely to occur, the implementation of a reasonable present
344 handler can gain performance significantly.
346 The informations exchanged between client and present handle are:
349 ## Client/server request:
351 HANDLE => ref, ## Reference to datastructure
352 SETNAME => "id", ## Result set ID
353 START => xxx, ## Start position
354 COMP => "", ## Desired record composition
355 NUMBER => yyy, ## Number of requested records
358 ## Respons parameters:
360 HITS => zzz, ## Number of returned records
361 ERR_CODE => 0, ## Error code
362 ERR_STR => "" ## Error message
368 The fetch handler is asked to retrieve a SINGLE record from a given
369 result set (the front-end server will automatically call the fetch
370 handler as many times as required).
372 The parameters exchanged between the server and the fetch handler are
375 ## Client/server request:
377 HANDLE => ref ## Reference to data structure
378 SETNAME => "id" ## ID of the requested result set
379 OFFSET => nnn ## Record offset number
380 REQ_FORM => "n.m.k.l"## Client requested format OID
381 COMP => "xyz" ## Formatting instructions
385 RECORD => "" ## Record string
386 BASENAME => "" ## Origin of returned record
387 LAST => 0 ## Last record in set?
388 ERR_CODE => 0 ## Error code
389 ERR_STR => "" ## Error string
390 SUR_FLAG => 0 ## Surrogate diagnostic flag
391 REP_FORM => "n.m.k.l"## Provided format OID
394 The REP_FORM value has by default the REQ_FORM value but can be set to
395 something different if the handler desires. The BASENAME value should
396 contain the name of the database from where the returned record originates.
397 The ERR_CODE and ERR_STR works the same way they do in the search
398 handler. If there is an error condition, the SUR_FLAG is used to
399 indicate whether the error condition pertains to the record currently
400 being retrieved, or whether it pertains to the operation as a whole
401 (eg. the client has specified a result set which does not exist.)
403 If you need to return USMARC records, you might want to have a look at
404 the MARC module on CPAN, if you don't already have a way of generating
407 NOTE: The record offset is 1-indexed - 1 is the offset of the first
412 A full featured Z39.50 server should support scan (or in some literature
413 browse). The client specifies a starting term of the scan, and the server
414 should return an ordered list of specified length consisting of terms
415 actually occurring in the data base. Each of these terms should be close
416 to or equal to the term originally specified. The quality of scan compared
417 to simple search is a guarantee of hits. It is simply like browsing through
418 an index of a book, you always find something! The parameters exchanged are
423 HANDLE => $ref ## Reference to data structure
424 TERM => 'start', ## The start term
425 NUMBER => xx, ## Number of requested terms
426 POS => yy, ## Position of starting point
427 ## within returned list
428 STEP => 0, ## Step size
432 ERR_CODE => 0, ## Error code
433 ERR_STR => '', ## Diagnostic message
434 NUMBER => zz, ## Number of returned terms
435 STATUS => $status, ## ScanSuccess/ScanFailure
436 ENTRIES => $entries ## Referenced list of terms
439 where the term list is returned by reference in the scalar $entries, which
440 should point at a data structure of this kind,
446 { TERM => 'energy density',
449 { TERM => 'energy flow',
457 The $status flag should be assigned one of two values:
459 Net::Z3950::SimpleServer::ScanSuccess On success (default)
460 Net::Z3950::SimpleServer::ScanPartial Less terms returned than requested
462 The STEP member contains the requested number of entries in the term-list
463 between two adjacent entries in the response.
467 The argument hash recieved by the close handler has one element only:
471 HANDLE => ref ## Reference to data structure
474 What ever data structure the HANDLE value points at goes out of scope
475 after this call. If you need to close down a connection to your server
476 or something similar, this is the place to do it.
480 Anders Sønderberg (sondberg@indexdata.dk) and Sebastian Hammer
481 (quinn@indexdata.dk).
487 Any Perl module which is useful for accessing the database of your