2 ## Copyright (c) 2000, Index Data.
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5 ## its documentation, in whole or in part, for any purpose, is hereby granted,
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28 package Net::Z3950::SimpleServer;
31 use vars qw($VERSION @ISA @EXPORT @EXPORT_OK);
38 @ISA = qw(Exporter AutoLoader DynaLoader);
39 # Items to export into callers namespace by default. Note: do not export
40 # names by default without a very good reason. Use EXPORT_OK instead.
41 # Do not simply export all your public functions/methods/constants.
47 bootstrap Net::Z3950::SimpleServer $VERSION;
49 # Preloaded methods go here.
55 my $args = shift || croak "SimpleServer::new: Usage new(argument hash)";
59 carp "SimpleServer.pm: WARNING: Multithreaded server unsupported";
63 $self->{INIT} = $args->{INIT};
64 $self->{SEARCH} = $args->{SEARCH} || croak "SimpleServer.pm: ERROR: Unspecified search handler";
65 $self->{FETCH} = $args->{FETCH} || croak "SimpleServer.pm: ERROR: Unspecified fetch handler";
66 $self->{CLOSE} = $args->{CLOSE};
77 if (defined($self->{INIT})) {
78 set_init_handler($self->{INIT});
80 set_search_handler($self->{SEARCH});
81 set_fetch_handler($self->{FETCH});
82 if (defined($self->{CLOSE})) {
83 set_close_handler($self->{CLOSE});
90 # Autoload methods go after =cut, and are processed by the autosplit program.
94 # Below is the stub of documentation for your module. You better edit it!
98 Net::Z3950::SimpleServer - Simple Perl API for building Z39.50 servers.
102 use Net::Z3950::SimpleServer;
104 sub my_search_handler {
107 my $set_id = $args->{SETNAME};
108 my @database_list = @{ $args->{DATABASES} };
109 my $query = $args->{QUERY};
111 ## Perform the query on the specified set of databases
112 ## and return the number of hits:
114 $args->{HITS} = $hits;
117 sub my_fetch_handler { # Get a record for the user
120 my $set_id = $args->{SETNAME};
122 my $record = fetch_a_record($args->{OFFSET);
124 $args->{RECORD} = $record;
125 $args->{LEN} = length($record);
126 if (number_of_hits() == $args->{OFFSET}) { ## Last record in set?
134 ## Register custom event handlers:
136 my $handle = Net::Z3950::SimpleServer->new({
137 INIT => \&my_init_handler,
138 CLOSE => \&my_close_handler,
139 SEARCH => \&my_search_handler,
140 FETCH => \&my_fetch_handler
144 $handle->launch_server("ztest.pl", @ARGV);
148 The SimpleServer module is a tool for constructing Z39.50 "Information
149 Retrieval" servers in Perl. The module is easy to use, but it
150 does help to have an understanding of the Z39.50 query
151 structure and the construction of structured retrieval records.
153 Z39.50 is a network protocol for searching remote databases and
154 retrieving the results in the form of structured "records". It is widely
155 used in libraries around the world, as well as in the US Federal Government.
156 In addition, it is generally useful whenever you wish to integrate a number
157 of different database systems around a shared, asbtract data model.
159 The model of the module is simple: It implements a "generic" Z39.50
160 server, which invokes callback functions supplied by you to search
161 for content in your database. You can use any tools available in
162 Perl to supply the content, including modules like DBI and
165 The server will take care of managing the network connections for
166 you, and it will spawn a new process (or thread, in some
167 environments) whenever a new connection is received.
169 The programmer can specify subroutines to take care of the following type
174 - Fetching of records
175 - Closing down connection
177 Note that only the Search and Fetch handler functions are required.
178 The module can supply default responses to the other on its own.
180 After the launching of the server, all control is given away from
181 the Perl script to the server. The server calls the registered
182 subroutines to field incoming requests from Z39.50 clients.
184 A reference to an anonymous hash is passed to each handle. Some of
185 the entries of these hashes are to be considered input and others
188 The Perl programmer specifies the event handles for the server by
189 means of the the SimpleServer object constructor
191 my $handle = Net::Z3950::SimpleServer->new({
192 INIT => \&my_init_handler,
193 CLOSE => \&my_close_handler,
194 SEARCH => \&my_search_handler,
195 FETCH => \&my_fetch_handler });
197 After the custom event handles are declared, the server is launched
198 by means of the method
200 $handle->launch_server("MyServer.pl", @ARGV);
202 Notice, the first argument should be the name of your server
203 script (for logging purposes), while the rest of the arguments
204 are documented in the YAZ toolkit manual: The section on
205 application invocation: <http://www.indexdata.dk/yaz/yaz-7.php>
209 The init handler is called whenever a Z39.50 client is attempting
210 to logon to the server. The exchange of parameters between the
211 server and the handler is carried out via an anonymous hash reached
216 The argument hash passed to the init handler has the form
219 ## Response parameters:
221 IMP_NAME => "" ## Z39.50 Implementation name
222 IMP_VER => "" ## Z39.50 Implementation version
223 ERR_CODE => 0 ## Error code, cnf. Z39.50 manual
224 HANDLE => undef ## Handler of Perl data structure
227 The HANDLE member can be used to store any scalar value which will then
228 be provided as input to all subsequent calls (ie. for searching, record
229 retrieval, etc.). A common use of the handle is to store a reference to
230 a hash which may then be used to store session-specific parameters.
231 If you have any session-specific information (such as a list of
232 result sets or a handle to a back-end search engine of some sort),
233 it is always best to store them in a private session structure -
234 rather than leaving them in global variables in your script.
236 The Implementation name and version are only really used by Z39.50
237 client developers to see what kind of server they're dealing with.
238 Filling these in is optional.
240 The ERR_CODE should be left at 0 (the default value) if you wish to
241 accept the connection. Any other value is interpreted as a failure
242 and the client will be shown the door.
244 =head2 Search handler
246 Similarly, the search handler is called with a reference to an anony-
247 mous hash. The structure is the following:
250 ## Request parameters:
252 HANDLE => ref ## Your session reference.
253 SETNAME => "id" ## ID of the result set
254 REPL_SET => 0 ## Replace set if already existing?
255 DATABASES => ["xxx"] ## Reference to a list of data-
257 QUERY => "query" ## The query expression
259 ## Response parameters:
261 ERR_CODE => 0 ## Error code (0=Succesful search)
262 ERR_STR => "" ## Error string
263 HITS => 0 ## Number of matches
266 Note that a search which finds 0 hits is considered successful in
267 Z39.50 terms - you should only set the ERR_CODE to a non-zero value
268 if there was a problem processing the request. The Z39.50 standard
269 provides a comprehensive list of standard diagnostic codes, and you
270 should use these whenever possible.
272 The QUERY is a tree-structure of terms combined by operators, the
273 terms being qualified by lists of attributes. The query is presented
274 to the search function in the Prefix Query Format (PQF) which is
275 used in many applications based on the YAZ toolkit. The full grammar
276 is described in the YAZ manual.
278 The following are all examples of valid queries in the PQF.
284 @or "dylan" "zimmerman"
288 @or @and bob dylan @set Result-1
290 @and @attr 1=1 "bob dylan" @attr 1=4 "slow train coming"
292 @attrset @attr 4=1 @attr 1=4 "self portrait"
294 You will need to write a recursive function or something similar to
295 parse incoming query expressions, and this is usually where a lot of
296 the work in writing a database-backend happens. Fortunately, you don't
297 need to support anymore functionality than you want to. For instance,
298 it is perfectly legal to not accept boolean operators, but you SHOULD
299 try to return good error codes if you run into something you can't or
304 The fetch handler is asked to retrieve a SINGLE record from a given
305 result set (the front-end server will automatically call the fetch
306 handler as many times as required).
308 The parameters exchanged between the server and the fetch handler are
311 ## Client/server request:
313 HANDLE => ref ## Reference to data structure
314 SETNAME => "id" ## ID of the requested result set
315 OFFSET => nnn ## Record offset number
316 REQ_FORM => "USMARC" ## Client requested record format
317 COMP => "xyz" ## Formatting instructions
321 RECORD => "" ## Record string
322 BASENAME => "" ## Origin of returned record
323 LAST => 0 ## Last record in set?
324 ERR_CODE => 0 ## Error code
325 ERR_STR => "" ## Error string
326 SUR_FLAG => 0 ## Surrogate diagnostic flag
327 REP_FORM => "USMARC" ## Provided record format
330 The REP_FORM value has by default the REQ_FORM value but can be set to
331 something different if the handler desires. The BASENAME value should
332 contain the name of the database from where the returned record originates.
333 The ERR_CODE and ERR_STR works the same way they do in the search
334 handler. If there is an error condition, the SUR_FLAG is used to
335 indicate whether the error condition pertains to the record currently
336 being retrieved, or whether it pertains to the operation as a whole
337 (eg. the client has specified a result set which does not exist.)
339 Record formats are currently carried as strings (eg. USMARC, TEXT_XML,
340 SUTRS), but this will probably change to proper OID strings in the
341 future (not to worry, though, the module will supply constant values
342 for the common OIDs). If you need to return USMARC records, you might
343 want to have a look at the MARC module on CPAN, if you don't already
344 have a way of generating these.
346 NOTE: The record offset is 1-indexed - 1 is the offset of the first
351 The argument hash recieved by the close handler has one element only:
355 HANDLE => ref ## Reference to data structure
358 What ever data structure the HANDLE value points at goes out of scope
359 after this call. If you need to close down a connection to your server
360 or something similar, this is the place to do it.
364 Anders Sønderberg (sondberg@indexdata.dk) and Sebastian Hammer
365 (quinn@indexdata.dk).
371 Any Perl module which is useful for accessing the database of your