1 # $Id: ZOOM.pod,v 1.23 2005-12-19 17:42:15 mike Exp $
8 ZOOM - Perl extension implementing the ZOOM API for Information Retrieval
14 $conn = new ZOOM::Connection($host, $port)
15 $conn->option(preferredRecordSyntax => "usmarc");
16 $rs = $conn->search_pqf('@attr 1=4 dinosaur');
18 print $rs->record(0)->render();
21 print "Error ", $@->code(), ": ", $@->message(), "\n";
26 This module provides a nice, Perlish implementation of the ZOOM
27 Abstract API described and documented at http://zoom.z3950.org/api/
29 the ZOOM module is implemented as a set of thin classes on top of the
30 non-OO functions provided by this distribution's C<Net::Z3950::ZOOM>
32 turn is a thin layer on top of the ZOOM-C code supplied as part of
33 Index Data's YAZ Toolkit. Because ZOOM-C is also the underlying code
34 that implements ZOOM bindings in C++, Visual Basic, Scheme, Ruby, .NET
35 (including C#) and other languages, this Perl module works compatibly
36 with those other implementations. (Of course, the point of a public
37 API such as ZOOM is that all implementations should be compatible
38 anyway; but knowing that the same code is running is reassuring.)
40 The ZOOM module provides two enumerations (C<ZOOM::Error> and
41 C<ZOOM::Event>), two utility functions C<diag_str()> and C<event()> in
42 the C<ZOOM> package itself, and eight classes:
52 Of these, the Query class is abstract, and has two concrete
57 Many useful ZOOM applications can be built using only the Connection,
58 ResultSet, Record and Exception classes, as in the example
61 A typical application will begin by creating an Connection object,
62 then using that to execute searches that yield ResultSet objects, then
63 fetching records from the result-sets to yield Record objects. If an
64 error occurs, an Exception object is thrown and can be dealt with.
66 More sophisticated applications might also browse the server's indexes
67 to create a ScanSet, from which indexed terms may be retrieved; others
68 might send ``Extended Services'' Packages to the server, to achieve
69 non-standard tasks such as database creation and record update.
70 Searching using a query syntax other than PQF can be done using an
71 query object of one of the Query subclasses. Finally, sets of options
72 may be manipulated independently of the objects they are associated
73 with using an Options object.
75 In general, method calls throw an exception if anything goes wrong, so
76 you don't need to test for success after each call. See the section
77 below on the Exception class for details.
79 =head1 UTILITY FUNCTIONS
81 =head2 ZOOM::diag_str()
83 $msg = ZOOM::diag_str(ZOOM::Error::INVALID_QUERY);
85 Returns a human-readable English-language string corresponding to the
86 error code that is its own parameter. This works for any error-code
88 C<ZOOM::Exception::code()>,
89 C<ZOOM::Connection::error_x()>
91 C<ZOOM::Connection::errcode()>,
92 irrespective of whether it is a member of the C<ZOOM::Error>
93 enumeration or drawn from the BIB-1 diagnostic set.
98 Lark's vomit. Do not read this section.
100 $which = ZOOM::event([ $conn1, $conn2, $conn3 ]);
102 Used only in complex asynchronous applications, this function takes a
103 reference to a list of Connection objects, waits until an event
104 occurs on any one of them, and returns an integer indicating which of
105 the connections it occurred on. The return value is a 1-based index
106 into the list; 0 is returned if no event occurs within the longest
107 timeout specified by the C<timeout> options of all the connections.
110 This function is not yet implemented.
114 The eight ZOOM classes are described here in ``sensible order'':
115 first, the four commonly used classes, in the he order that they will
116 tend to be used in most programs (Connection, ResultSet, Record,
117 Exception); then the four more esoteric classes in descending order of
118 how often they are needed.
120 With the exception of the Options class, which is an extension to the
121 ZOOM model, the introduction to each class includes a link to the
122 relevant section of the ZOOM Abstract API.
124 =head2 ZOOM::Connection
126 $conn = new ZOOM::Connection("indexdata.dk:210/gils");
127 print("server is '", $conn->option("serverImplementationName"), "'\n");
128 $conn->option(preferredRecordSyntax => "usmarc");
129 $rs = $conn->search_pqf('@attr 1=4 mineral');
130 $ss = $conn->scan('@attr 1=1003 a');
131 if ($conn->errcode() != 0) {
132 die("somthing went wrong: " . $conn->errmsg())
136 This class represents a connection to an information retrieval server,
137 using an IR protocol such as ANSI/NISO Z39.50, SRW (the
138 Search/Retrieve Webservice), SRU (the Search/Retrieve URL) or
139 OpenSearch. Not all of these protocols require a low-level connection
140 to be maintained, but the Connection object nevertheless provides a
141 location for the necessary cache of configuration and state
142 information, as well as a uniform API to the connection-oriented
143 facilities (searching, index browsing, etc.), provided by these
146 See the description of the C<Connection> class in the ZOOM Abstract
148 http://zoom.z3950.org/api/zoom-current.html#3.2
154 $conn = new ZOOM::Connection("indexdata.dk", 210);
155 $conn = new ZOOM::Connection("indexdata.dk:210/gils");
156 $conn = new ZOOM::Connection("tcp:indexdata.dk:210/gils");
157 $conn = new ZOOM::Connection("http:indexdata.dk:210/gils");
159 Creates a new Connection object, and immediately connects it to the
160 specified server. If you want to make a new Connection object but
161 delay forging the connection, use the C<create()> and C<connect()>
164 This constructor can be called with two arguments or a single
165 argument. In the former case, the arguments are the name and port
166 number of the Z39.50 server to connect to; in the latter case, the
167 single argument is a YAZ service-specifier string of the form
173 [I<scheme>:]I<host>[:I<port>][/I<databaseName>]
177 In which the I<host> and I<port> parts are as in the two-argument
178 form, the I<databaseName> if provided specifies the name of the
179 database to be used in subsequent searches on this connection, and the
180 optional I<scheme> (default C<tcp>) indicates what protocol should be
181 used. At present, the following schemes are supported:
191 Z39.50 connection encrypted using SSL (Secure Sockets Layer). Not
192 many servers support this, but Index Data's Zebra is one that does.
196 Z39.50 connection on a Unix-domain (local) socket, in which case the
197 I<hostname> portion of the string is instead used as a filename in the
202 SRW connection using SOAP over HTTP.
206 Support for SRU will follow in the fullness of time.
208 If an error occurs, an exception is thrown. This may indicate a
209 networking problem (e.g. the host is not found or unreachable), or a
210 protocol-level problem (e.g. a Z39.50 server rejected the Init
213 =head4 create() / connect()
215 $options = new ZOOM::Options();
216 $options->option(implementationName => "my client");
217 $conn = create ZOOM::Connection($options)
218 $conn->connect($host, 0);
220 The usual Connection constructor, C<new()> brings a new object into
221 existence and forges the connection to the server all in one
222 operation, which is often what you want. For applications that need
223 more control, however, these two method separate the two steps,
224 allowing additional steps in between such as the setting of options.
226 C<create()> creates and returns a new Connection object, which is
227 I<not> connected to any server. It may be passed an options block, of
228 type C<ZOOM::Options> (see below), into which options may be set
229 before or after the creation of the Connection. The connection to the
230 server may then be forged by the C<connect()> method, the arguments of
231 which are the same as those of the C<new()> constructor.
233 =head4 error_x() / errcode() / errmsg() / addinfo() / diagset()
235 ($errcode, $errmsg, $addinfo, $diagset) = $conn->error_x();
236 $errcode = $conn->errcode();
237 $errmsg = $conn->errmsg();
238 $addinfo = $conn->addinfo();
239 $diagset = $conn->diagset();
241 These methods may be used to obtain information about the last error
242 to have occurred on a connection - although typically they will not
243 been used, as the same information is available through the
244 C<ZOOM::Exception> that is thrown when the error occurs. The
250 methods each return one element of the diagnostic, and
252 returns all four at once.
254 See the C<ZOOM::Exception> for the interpretation of these elements.
256 =head4 option() / option_binary()
258 print("server is '", $conn->option("serverImplementationName"), "'\n");
259 $conn->option(preferredRecordSyntax => "usmarc");
260 $conn->option_binary(iconBlob => "foo\0bar");
261 die if length($conn->option_binary("iconBlob") != 7);
263 Objects of the Connection, ResultSet, ScanSet and Package classes
264 carry with them a set of named options which affect their behaviour in
265 certain ways. See the ZOOM-C options documentation for details:
267 Connection options are listed at
268 http://indexdata.com/yaz/doc/zoom.tkl#zoom.connections
270 These options are set and fetched using the C<option()> method, which
271 may be called with either one or two arguments. In the two-argument
272 form, the option named by the first argument is set to the value of
273 the second argument, and its old value is returned. In the
274 one-argument form, the value of the specified option is returned.
276 For historical reasons, option values are not binary-clean, so that a
277 value containing a NUL byte will be returned in truncated form. The
278 C<option_binary()> method behaves identically to C<option()> except
279 that it is binary-clean, so that values containing NUL bytes are set
280 and returned correctly.
282 =head4 search() / search_pqf()
284 $rs = $conn->search(new ZOOM::Query::CQL('title=dinosaur'));
285 # The next two lines are equivalent
286 $rs = $conn->search(new ZOOM::Query::PQF('@attr 1=4 dinosaur'));
287 $rs = $conn->search_pqf('@attr 1=4 dinosaur');
289 The principal purpose of a search-and-retrieve protocol is searching
290 (and, er, retrieval), so the principal method used on a Connection
291 object is C<search()>. It accepts a single argument, a C<ZOOM::Query>
292 object (or, more precisely, an object of a subclass of this class);
293 and it creates and returns a new ResultSet object representing the set
294 of records resulting from the search.
296 Since queries using PQF (Prefix Query Format) are so common, we make
297 them a special case by providing a C<search_prefix()> method. This is
298 identical to C<search()> except that it accepts a string containing
299 the query rather than an object, thereby obviating the need to create
300 a C<ZOOM::Query::PQF> object. See the documentation of that class for
301 information about PQF.
303 =head4 scan() / scan1()
305 ### Code sample needed here!
307 Many Z39.50 servers allow you to browse their indexes to find terms to
308 search for. This is done using the C<scan> method, which creates and
309 returns a new ScanSet object representing the set of terms resulting
312 C<scan()> takes a single argument, but it has to work hard: it
313 specifies both what index to scan for terms, and where in the index to
314 start scanning. What's more, the specification of what index to scan
315 includes multiple facets, such as what database fields it's an index
316 of (author, subject, title, etc.) and whether to scan for whole fields
317 or single words (e.g. the title ``I<The Empire Strikes Back>'', or the
318 four words ``Back'', ``Empire'', ``Strikes'' and ``The'', interleaved
319 with words from other titles in the same index.
321 All of this is done by using a single term from the PQF query as the
322 C<scan()> argument. (At present, only PQF is supported, although
323 there is no reason in principle why CQL and other query syntaxes
324 should not be supported in future). The attributes associated with
325 the term indicate which index is to be used, and the term itself
326 indicates the point in the index at which to start the scan. For
327 example, if the argument is C<@attr 1=4 fish>, then
333 This is the BIB-1 attribute with type 1 (meaning access-point, which
334 specifies an index), and type 4 (which means ``title''). So the scan
335 is in the title index.
339 Start the scan from the lexicographically earliest term that is equal
340 to or falls after ``fish''.
344 The argument C<@attr 1=4 @attr 6=3 fish> would behave similarly; but
345 the BIB-1 attribute 6=3 mean completeness=``complete field'', so the
346 scan would be for complete titles rather than for words occurring in
349 This takes a bit of getting used to.
351 The behaviour is C<scan()> is affected by the following options, which
352 may be set on the Connection through which the scan is done:
356 =item number [default: 10]
358 Indicates how many terms should be returned in the ScanSet. The
359 number actually returned may be less, if the start-point is near the
360 end of the index, but will not be greater.
362 =item position [default: 1]
364 A 1-based index specifying where in the returned list of terms the
365 seed-term should appear. By default it should be the first term
366 returned, but C<position> may be set, for example, to zero (requesting
367 the next terms I<after> the seed-term), or to the same value as
368 C<number> (requesting the index terms I<before> the seed term).
370 =item stepSize [default: 0]
372 An integer indicating how many indexed terms are to be skipped between
373 each one returned in the ScanSet. By default, no terms are skipped,
374 but overriding this can be useful to get a high-level overview of the
377 The C<scan1()> method is the same as C<scan()> except that it takes a
378 Query object as its argument instead of a PQF string. This means
379 that it can be used to scan using a CQL term, so long as the
380 underlying ZOOM-C library supports this.
386 $p = $conn->package();
387 $o = new ZOOM::Options();
388 $o->option(databaseName => "newdb");
389 $p = $conn->package($o);
391 Creates and returns a new C<ZOOM::Package>, to be used in invoking an
392 Extended Service. An options block may optionally be passed in. See
393 the C<ZOOM::Package> documentation.
397 if ($conn->last_event() == ZOOM::Event::CONNECT) {
398 print "Connected!\n";
401 Returns a C<ZOOM::Event> enumerated value indicating the type of the
402 last event that occurred on the connection. This is used only in
403 complex asynchronous applications - see the section below on
404 C<ZOOM::Event> for more information.
407 This method has not been tested.
413 Destroys a Connection object, tearing down any low-level connection
414 associated with it and freeing its resources. It is an error to reuse
415 a Connection that has been C<destroy()>ed.
417 =head2 ZOOM::ResultSet
419 $rs = $conn->search_pqf('@attr 1=4 mineral');
422 $rec = $rs->record($i-1);
423 print $rec->render();
426 A ResultSet object represents the set of zero or more records
427 resulting from a search, and is the means whereby these records can be
428 retrieved. A ResultSet object may maintain client side cache or some,
429 less, none, all or more of the server's records: in general, this is
430 supposed to an implementaton detail of no interest to a typical
431 application, although more sophisticated applications do have
432 facilities for messing with the cache. Most applications will only
433 need the C<size()>, C<record()> and C<sort()> methods.
435 There is no C<new()> method nor any other explicit constructor. The
436 only way to create a new ResultSet is by using C<search()> (or
437 C<search_prefix()>) on a Connection.
439 See the description of the C<Result Set> class in the ZOOM Abstract
441 http://zoom.z3950.org/api/zoom-current.html#3.4
447 $rs->option(elementSetName => "f");
449 Allows options to be set into, and read from, a ResultSet, just like
450 the Connection class's C<option()> method. There is no
451 C<option_binary()> method for ResultSet objects.
453 ResultSet options are listed at
454 http://indexdata.com/yaz/doc/zoom.resultsets.tkl
458 print "Found ", $rs->size(), " records\n";
460 Returns the number of records in the result set.
462 =head4 record() / record_immediate()
464 $rec = $rs->record(0);
465 $rec2 = $rs->record_immediate(0);
466 $rec3 = $rs->record_immediate(1)
467 or print "second record wasn't in cache\n";
469 The C<record()> method returns a C<ZOOM::Record> object representing
470 a record from result-set, whose position is indicated by the argument
471 passed in. This is a zero-based index, so that legitimate values
472 range from zero to C<$rs->size()-1>.
474 The C<record_immediate()> API is identical, but it never invokes a
475 network operation, merely returning the record from the ResultSet's
476 cache if it's already there, or an undefined value otherwise. So if
477 you use this method, B<you must always check the return value>.
481 $rs->records(0, 10, 0);
483 print $rs->record_immediate($i)->render();
486 @nextseven = $rs->records(10, 7, 1);
488 The C<record_immediate()> method only fetches records from the cache,
489 whereas C<record()> fetches them from the server if they have not
490 already been cached; but the ZOOM module has to guess what the most
491 efficient strategy for this is. It might fetch each record, alone
492 when asked for: that's optimal in an application that's only
493 interested in the top hit from each search, but pessimal for one that
494 wants to display a whole list of results. Conversely, the software's
495 strategy might be always to ask for blocks of a twenty records:
496 that's great for assembling long lists of things, but wasteful when
497 only one record is wanted. The problem is that the ZOOM module can't
498 tell, when you call C<$rs->record()>, what your intention is.
500 But you can tell it. The C<records()> method fetches a sequence of
501 records, all in one go. It takes three arguments: the first is the
502 zero-based index of the first record in the sequence, the second is
503 the number of records to fetch, and the third is a boolean indication
504 of whether or not to return the retrieved records as well as adding
505 them to the cache. (You can always pass 1 for this if you like, and
506 Perl will discard the unused return value, but there is a small
507 efficiency gain to be had by passing 0.)
509 Once the records have been retrieved from the server
510 (i.e. C<records()> has completed without throwing an exception), they
511 can be fetched much more efficiently using C<record()> - or
512 C<record_immediate()>, which is then guaranteed to succeed.
518 Resets the ResultSet's record cache, so that subsequent invocations of
519 C<record_immediate()> will fail. I struggle to imagine a real
520 scenario where you'd want to do this.
524 if ($rs->sort("yaz", "1=4 >i 1=21 >s") < 0) {
528 Sorts the ResultSet in place (discarding any cached records, as they
529 will in general be sorted into a different position). There are two
530 arguments: the first is a string indicating the type of the
531 sort-specification, and the second is the specification itself.
533 The C<sort()> method returns 0 on success, or -1 if the
534 sort-specification is invalid.
536 At present, the only supported sort-specification type is C<yaz>.
537 Such a specification consists of a space-separated sequence of keys,
538 each of which itself consists of two space-separated words (so that
539 the total number of words in the sort-specification is even). The two
540 words making up each key are a field and a set of flags. The field
541 can take one of two forms: if it contains an C<=> sign, then it is a
542 BIB-1 I<type>=I<value> pair specifying which field to sort
543 (e.g. C<1=4> for a title sort); otherwise it is sent for the server to
544 interpret as best it can. The word of flags is made up from one or
545 more of the following: C<s> for case sensitive, C<i> for case
546 insensitive; C<<> for ascending order and C<E<gt>> for descending
549 For example, the sort-specification in the code-fragment above will
550 sort the records in C<$rs> case-insensitively in descending order of
551 title, with records having equivalent titles sorted case-sensitively
552 in ascending order of subject. (The BIB-1 access points 4 and 21
553 represent title and subject respectively.)
559 Destroys a ResultSet object, freeing its resources. It is an error to
560 reuse a ResultSet that has been C<destroy()>ed.
564 $rec = $rs->record($i);
565 print $rec->render();
567 $marc = new_from_usmarc MARC::Record($raw);
568 print "Record title is: ", $marc->title(), "\n";
570 A Record object represents a record that has been retrived from the
573 There is no C<new()> method nor any other explicit constructor. The
574 only way to create a new Record is by using C<record()> (or
575 C<record_immediate()>, or C<records()>) on a ResultSet.
577 In general, records are ``owned'' by their result-sets that they were
578 retrieved from, so they do not have to be explicitly memory-managed:
579 they are deallocated (and therefore can no longer be used) when the
580 result-set is destroyed.
582 See the description of the C<Record> class in the ZOOM Abstract
584 http://zoom.z3950.org/api/zoom-current.html#3.5
592 Returns a human-readable representation of the record. Beyond that,
593 no promises are made: careful programs should not make assumptions
594 about the format of the returned string.
596 This method is useful mostly for debugging.
602 $marc = new_from_usmarc MARC::Record($raw);
604 Returns an opaque blob of data that is the raw form of the record.
605 Exactly what this is, and what you can do with it, varies depending on
606 the record-syntax. For example, XML records will be returned as,
607 well, XML; MARC records will be returned as ISO 2709-encoded blocks
608 that can be decoded by software such as the fine C<Marc::Record>
609 module; GRS-1 record will be ... gosh, what an interesting question.
610 But no-one uses GRS-1 any more, do they?
612 =head4 clone() / destroy()
614 $rec = $rs->record($i);
615 $newrec = $rec->clone();
617 print $newrec->render();
620 Usually, it's convenient that Record objects are owned by their
621 ResultSets and go away when the ResultSet is destroyed; but
622 occasionally you need a Record to outlive its parent and destroy it
623 later, explicitly. To do this, C<clone()> the record, keep the new
624 Record object that is returned, and C<destroy()> it when it's no
625 longer needed. This is B<only> situation in which a Record needs to
628 =head2 ZOOM::Exception
630 In general, method calls throw an exception (of class
631 C<ZOOM::Exception>) if anything goes wrong, so you don't need to test
632 for success after each call. Exceptions are caught by enclosing the
633 main code in an C<eval{}> block and checking C<$@> on exit from that
634 block, as in the code-sample above.
636 There are a small number of exceptions to this rule: the three
637 record-fetching methods in the C<ZOOM::ResultSet> class,
639 C<record_immediate()>,
642 can all return undefined values for legitimate reasons, under
643 circumstances that do not merit throwing an exception. For this
644 reason, the return values of these methods should be checked. See the
645 individual methods' documentation for details.
647 An exception carries the following pieces of information:
653 A numeric code that specifies the type of error. This can be checked
654 for equality with known values, so that intelligent applications can
655 take appropriate action.
659 A human-readable message corresponding with the code. This can be
660 shown to users, but its value should not be tested, as it could vary
661 in different versions or under different locales.
663 =item additional information [optional]
665 A string containing information specific to the error-code. For
666 example, when the error-code is the BIB-1 diagnostic 109 ("Database
667 unavailable"), the additional information is the name of the database
668 that the application tried to use. For some error-codes, there is no
669 additional information at all; for some others, the additional
670 information is undefined and may just be an human-readable string.
672 =item diagnostic set [optional]
674 A short string specifying the diagnostic set from which the error-code
675 was drawn: for example, C<ZOOM> for a ZOOM-specific error such as
676 C<ZOOM::Error::MEMORY> ("out of memory"), and C<BIB-1> for a Z39.50
677 error-code drawn from the BIB-1 diagnostic set.
681 In theory, the error-code should be interpreted in the context of the
682 diagnostic set from which it is drawn; in practice, nearly all errors
683 are from either the ZOOM or BIB-1 diagnostic sets, and the codes in
684 those sets have been chosen so as not to overlap, so the diagnostic
685 set can usually be ignored.
687 See the description of the C<Exception> class in the ZOOM Abstract
689 http://zoom.z3950.org/api/zoom-current.html#3.7
695 die new ZOOM::Exception($errcode, $errmsg, $addinfo, $diagset);
697 Creates and returns a new Exception object with the specified
698 error-code, error-message, additional information and diagnostic set.
699 Applications will not in general need to use this, but may find it
700 useful to simulate ZOOM exceptions. As is usual with Perl, exceptions
701 are thrown using C<die()>.
703 =head4 code() / message() / addinfo() / diagset()
705 print "Error ", $@->code(), ": ", $@->message(), "\n";
706 print "(addinfo '", $@->addinfo(), "', set '", $@->diagset(), "')\n";
708 These methods, of no arguments, return the exception's error-code,
709 error-message, additional information and diagnostic set respectively.
715 Returns a human-readable rendition of an exception. The C<"">
716 operator is overloaded on the Exception class, so that an Exception
717 used in a string context is automatically rendered. Among other
718 consequences, this has the useful result that a ZOOM application that
719 died due to an uncaught exception will emit an informative message
724 $ss = $conn->scan('@attr 1=1003 a');
726 ($term, $occ) = $ss->term($n-1);
727 $rs = $conn->search_pqf('@attr 1=1003 "' . $term . "'");
728 assert($rs->size() == $occ);
730 A ScanSet represents a set of candidate search-terms returned from an
731 index scan. Its sole purpose is to provide access to those term, to
732 the corresponding display terms, and to the occurrence-counts of the
735 There is no C<new()> method nor any other explicit constructor. The
736 only way to create a new ScanSet is by using C<scan()> on a
739 See the description of the C<Scan Set> class in the ZOOM Abstract
741 http://zoom.z3950.org/api/zoom-current.html#3.6
747 print "Found ", $ss->size(), " terms\n";
749 Returns the number of terms in the scan set. In general, this will be
750 the scan-set size requested by the C<number> option in the Connection
751 on which the scan was performed [default 10], but it may be fewer if
752 the scan is close to the end of the index.
754 =head4 term() / display_term()
756 $ss = $conn->scan('@attr 1=1004 whatever');
757 ($term, $occurrences) = $ss->term(0);
758 ($displayTerm, $occurrences2) = $ss->display_term(0);
759 assert($occurrences == $occurrences2);
760 if (user_likes_the_look_of($displayTerm)) {
761 $rs = $conn->search_pqf('@attr 1=4 "' . $term . '"');
762 assert($rs->size() == $occurrences);
765 These methods return the scanned terms themselves. C<term()> returns
766 the term is a form suitable for submitting as part of a query, whereas
767 C<display_term()> returns it in a form suitable for displaying to a
768 user. Both versions also return the number of occurrences of the term
769 in the index, i.e. the number of hits that will be found if the term
770 is subsequently used in a query.
772 In most cases, the term and display term will be identical; however,
773 they may be different in cases where punctuation or case is
774 normalised, or where identifiers rather than the original document
779 print "scan status is ", $ss->option("scanStatus");
781 Allows options to be set into, and read from, a ScanSet, just like
782 the Connection class's C<option()> method. There is no
783 C<option_binary()> method for ScanSet objects.
785 ScanSet options are also described, though not particularly
787 http://indexdata.com/yaz/doc/zoom.scan.tkl
793 Destroys a ScanSet object, freeing its resources. It is an error to
794 reuse a ScanSet that has been C<destroy()>ed.
798 $p = $conn->package();
799 $p->option(action => "specialUpdate");
800 $p->option(recordIdOpaque => 145);
801 $p->option(record => content_of("/tmp/record.xml"));
805 This class represents an Extended Services Package: an instruction to
806 the server to do something not covered by the core parts of the Z39.50
807 standard (or the equivalent in SRW or SRU). Since the core protocols
808 are read-only, such requests are often used to make changes to the
809 database, such as in the record update example above.
811 Requesting an extended service is a four-step process: first, create a
812 package associated with the connection to the relevant database;
813 second, set options on the package to instruct the server on what to
814 do; third, send the package (which may result in an exception being
815 thrown if the server cannot execute the requested operations; and
816 finally, destroy the package.
818 Package options are listed at
819 http://indexdata.com/yaz/doc/zoom.ext.html
821 The particular options that have meaning are determined by the
822 top-level operation string specified as the argument to C<send()>.
823 For example, when the operation is C<update> (the most commonly used
824 extended service), the C<action> option may be set to any of
826 (add a new record, failing if that record already exists),
828 (delete a record, failing if it is not in the database).
830 (replace a record, failing if an old version is not already present)
833 (add a record, replacing any existing version that may be present).
835 For update, the C<record> option should be set to the full text of the
836 XML record to added, deleted or replaced. Depending on how the server
837 is configured, it may extract the record's unique ID from the text
838 (i.e. from a known element such as the C<001> field of a MARCXML
839 record), or it may require the unique ID to passed in explicitly using
840 the C<recordIdOpaque> option.
842 Extended services packages are B<not currently described> in the ZOOM
844 http://zoom.z3950.org/api/zoom-current.html
845 They will be added in a forthcoming version, and will function much
846 as those implemented in this module.
852 $p->option(recordIdOpaque => "46696f6e61");
854 Allows options to be set into, and read from, a Package, just like
855 the Connection class's C<option()> method. There is no
856 C<option_binary()> method for Package objects.
858 Package options are listed at
859 http://indexdata.com/yaz/doc/zoom.ext.tkl
863 $p->send("createdb");
865 Sends a package to the server associated with the Connection that
866 created it. Problems are reported by throwing an exception. The
867 single parameter indicates the operation that the server is being
868 requested to perform, and controls the interpretation of the package's
869 options. Valid operations include:
875 Request a copy of a nominated object, e.g. place an ILL request.
879 Create a new database, the name of which is specified by the
880 C<databaseName> option.
884 Drop an existing database, the name of which is specified by the
885 C<databaseName> option.
889 Commit changes made to the database within a transaction.
893 Modify the contents of the database by adding, deleting or replacing
894 records (as described above in the overview of the C<ZOOM::Package>
899 I have no idea what this does.
903 Although the module is capable of I<making> all these requests, not
904 all servers are capable of I<executing> them. Refusal is indicated by
905 throwing an exception. Problems may also be caused by lack of
906 privileges; so C<send()> must be used with caution, and is perhaps
907 best wrapped in a clause that checks for execptions, like so:
909 eval { $p->send("create") };
910 if ($@ && $@->isa("ZOOM::Exception")) {
911 print "Oops! ", $@->message(), "\n";
919 Destroys a Package object, freeing its resources. It is an error to
920 reuse a Package that has been C<destroy()>ed.
924 $q = new ZOOM::Query::CQL("creator=pike and subject=unix");
925 $q->sortby("1=4 >i 1=21 >s");
926 $rs = $conn->search($q);
929 C<ZOOM::Query> is a virtual base class from which various concrete
930 subclasses can be derived. Different subclasses implement different
931 types of query. The sole purpose of a Query object is to be used in a
932 C<search()> on a Connection; because PQF is such a common special
933 case, the shortcut Connection method C<search_pqf()> is provided.
935 The following Query subclasses are provided, both of the providing the
936 same set of methods described below:
940 =item ZOOM::Query::PQF
942 Implements Prefix Query Format (PQF), also sometimes known as Prefix
943 Query Notation (PQN). This esoteric but rigorous and expressive
944 format is described in the YAZ Manual at
945 http://indexdata.com/yaz/doc/tools.tkl#PQF
947 =item ZOOM::Query::CQL
949 Implements the Common Query Language (CQL) of SRU, the Search/Retrieve
950 URL. CQL is a much friendlier notation than PQF, using a simple infix
951 notation. The queries are passed ``as is'' to the server rather than
952 being compiled into a Z39.50 Type-1 query, so only CQL-compliant
953 servers can support such querier. CQL is described at
954 http://www.loc.gov/standards/sru/cql/
955 and in a slight out-of-date but nevertheless useful tutorial at
956 http://zing.z3950.org/cql/intro.html
960 See the description of the C<Query> class in the ZOOM Abstract
962 http://zoom.z3950.org/api/zoom-current.html#3.3
968 $q = new ZOOM::Query::CQL('title=dinosaur'));
969 $q = new ZOOM::Query::PQF('@attr 1=4 dinosaur'));
971 Creates a new query object, compiling the query passed as its argument
972 according to the rules of the particular query-type being
973 instantiated. If compilation fails, an exception is thrown.
974 Otherwise, the query may be passed to the C<Connection> method
979 $q->sortby("1=4 >i 1=21 >s");
981 Sets a sort specification into the query, so that when a C<search()>
982 is run on the query, the result is automatically sorted. The sort
983 specification language is the same as the C<yaz> sort-specification
984 type of the C<ResultSet> method C<sort()>, described above.
986 B<It ought to be possible to sort by CQL query, too, but at present
987 limitations in the underlying ZOOM-C library make this impossible.>
993 Destroys a Query object, freeing its resources. It is an error to
994 reuse a Query that has been C<destroy()>ed.
998 $o1 = new ZOOM::Options();
999 $o1->option(user => "alf");
1000 $o2 = new ZOOM::Options();
1001 $o2->option(password => "fruit");
1002 $opts = new ZOOM::Options($o1, $o2);
1003 $conn = create ZOOM::Connection($opts);
1004 $conn->connect($host); # Uses the specified username and password
1006 Several classes of ZOOM objects carry their own sets of options, which
1007 can be manipulated using their C<option()> method. Sometimes,
1008 however, it's useful to deal with the option sets directly, and the
1009 C<ZOOM::Options> class exists to enable this approach.
1011 Option sets are B<not currently described> in the ZOOM
1013 http://zoom.z3950.org/api/zoom-current.html
1014 They are an extension to that specification.
1020 $o1 = new ZOOM::Options();
1021 $o1and2 = new ZOOM::Options($o1);
1022 $o3 = new ZOOM::Options();
1023 $o1and3and4 = new ZOOM::Options($o1, $o3);
1025 Creates and returns a new option set. One or two (but no more)
1026 existing option sets may be passed as arguments, in which case they
1027 become ``parents'' of the new set, which thereby ``inherits'' their
1028 options, the values of the first parent overriding those of the second
1029 when both have a value for the same key. An option set that inherits
1030 from a parent that has its own parents also inherits the grandparent's
1033 =head4 option() / option_binary()
1035 $o->option(preferredRecordSyntax => "usmarc");
1036 $o->option_binary(iconBlob => "foo\0bar");
1037 die if length($o->option_binary("iconBlob") != 7);
1039 These methods are used to get and set options within a set, and behave
1040 the same way as the same-named C<Connection> methods - see above. As
1041 with the C<Connection> methods, values passed to and retrieved using
1042 C<option()> are interpreted as NUL-terminated, while those passed to
1043 and retrieved from C<option_binary()> are binary-clean.
1047 $o->option(x => "T");
1048 $o->option(y => "F");
1049 assert($o->bool("x", 1));
1050 assert(!$o->bool("y", 1));
1051 assert($o->bool("z", 1));
1053 The first argument is a key, and the second is a default value.
1054 Returns the value associated with the specified key as a boolean, or
1055 the default value if the key has not been set. The values C<T> (upper
1056 case) and C<1> are considered true; all other values (including C<t>
1057 (lower case) and non-zero integers other than one) are considered
1060 This method is provided in ZOOM-C because in a statically typed
1061 language it's convenient to have the result returned as an
1062 easy-to-test type. In a dynamically typed language such as Perl, this
1063 problem doesn't arise, so C<bool()> is nearly useless; but it is made
1064 available in case applications need to duplicate the idiosyncratic
1065 interpretation of truth and falsehood and ZOOM-C uses.
1069 $o->option(x => "012");
1070 assert($o->int("x", 20) == 12);
1071 assert($o->int("y", 20) == 20);
1073 Returns the value associated with the specified key as an integer, or
1074 the default value if the key has not been set. See the description of
1075 C<bool()> for why you almost certainly don't want to use this.
1079 $o->set_int(x => "29");
1081 Sets the value of the specified option as an integer. Of course, Perl
1082 happily converts strings to integers on its own, so you can just use
1083 C<option()> for this, but C<set_int()> is guaranteed to use the same
1084 string-to-integer conversion as ZOOM-C does, which might occasionally
1085 be useful. Though I can't imagine how.
1087 =head4 set_callback()
1091 return "$udata-$key-$udata";
1093 $o->set_callback(\&cb, "xyz");
1094 assert($o->option("foo") eq "xyz-foo-xyz");
1096 This method allows a callback function to be installed in an option
1097 set, so that the values of options can be calculated algorithmically
1098 rather than, as usual, looked up in a table. Along with the callback
1099 function itself, an additional datum is provided: when an option is
1100 subsequently looked up, this datum is passed to the callback function
1101 along with the key; and its return value is returned to the caller as
1102 the value of the option.
1105 Although it ought to be possible to specify callback function using
1106 the C<\&name> syntax above, or a literal C<sub { code }> code
1107 reference, the complexities of the Perl-internal memory management
1108 system mean that the function must currently be specified as a string
1109 containing the fully-qualified name, e.g. C<"main::cb">.>
1112 The current implementation of the this method leaks memory, not only
1113 when the callback is installed, but on every occasion that it is
1114 consulted to look up an option value.
1120 Destroys an Options object, freeing its resources. It is an error to
1121 reuse an Options object that has been C<destroy()>ed.
1125 The ZOOM module provides two enumerations that list possible return
1126 values from particular functions. They are described in the following
1131 if ($@->code() == ZOOM::Error::QUERY_PQF) {
1132 return "your query was not accepted";
1135 This class provides a set of manifest constants representing some of
1136 the possible error codes that can be raised by the ZOOM module. The
1137 methods that return error-codes are
1138 C<ZOOM::Exception::code()>,
1139 C<ZOOM::Connection::error_x()>
1141 C<ZOOM::Connection::errcode()>.
1143 The C<ZOOM::Error> class provides the constants
1153 C<UNSUPPORTED_PROTOCOL>,
1154 C<UNSUPPORTED_QUERY>,
1164 each of which specifies a client-side error. These codes constitute
1165 the C<ZOOM> diagnostic set.
1167 Since errors may also be diagnosed by the server, and returned to the
1168 client, error codes may also take values from the BIB-1 diagnostic set
1169 of Z39.50, listed at the Z39.50 Maintenance Agency's web-site at
1170 http://www.loc.gov/z3950/agency/defns/bib1diag.html
1172 All error-codes, whether client-side from the C<ZOOM::Error>
1173 enumeration or server-side from the BIB-1 diagnostic set, can be
1174 translated into human-readable messages by passing them to the
1175 C<ZOOM::diag_str()> utility function.
1179 if ($conn->last_event() == ZOOM::Event::CONNECT) {
1180 print "Connected!\n";
1183 In applications that need it - mostly complex multiplexing
1184 applications - The C<ZOOM::Connection::last_event()> method is used to
1185 return an indication of the last event that occurred on a particular
1186 connection. It always returns a value drawn from this enumeration,
1187 that is, one of C<NONE>, C<CONNECT>, C<SEND_DATA>, C<RECV_DATA>,
1188 C<TIMEOUT>, C<UNKNOWN>, C<SEND_APDU>, C<RECV_APDU>, C<RECV_RECORD> or
1191 You almost certainly don't need to know about this. Frankly, I'm not
1192 sure how to use it myself.
1196 The ZOOM abstract API,
1197 http://zoom.z3950.org/api/zoom-current.html
1199 The C<Net::Z3950::ZOOM> module, included in the same distribution as this one.
1201 The C<Net::Z3950> module, which this one supersedes.
1202 http://perl.z3950.org/
1204 The documentation for the ZOOM-C module of the YAZ Toolkit, which this
1205 module is built on. Specifically, its lists of options are useful.
1206 http://indexdata.com/yaz/doc/zoom.tkl
1208 The BIB-1 diagnostic set of Z39.50,
1209 http://www.loc.gov/z3950/agency/defns/bib1diag.html
1213 Mike Taylor, E<lt>mike@indexdata.comE<gt>
1215 =head1 COPYRIGHT AND LICENCE
1217 Copyright (C) 2005 by Index Data.
1219 This library is free software; you can redistribute it and/or modify
1220 it under the same terms as Perl itself, either Perl version 5.8.4 or,
1221 at your option, any later version of Perl 5 you may have available.