1 # $Id: ZOOM.pod,v 1.33 2006-04-11 16:40:08 mike Exp $
8 ZOOM - Perl extension implementing the ZOOM API for Information Retrieval
14 $conn = new ZOOM::Connection($host, $port,
15 databaseName => "mydb");
16 $conn->option(preferredRecordSyntax => "usmarc");
17 $rs = $conn->search_pqf('@attr 1=4 dinosaur');
19 print $rs->record(0)->render();
22 print "Error ", $@->code(), ": ", $@->message(), "\n";
27 This module provides a nice, Perlish implementation of the ZOOM
28 Abstract API described and documented at http://zoom.z3950.org/api/
30 the ZOOM module is implemented as a set of thin classes on top of the
31 non-OO functions provided by this distribution's C<Net::Z3950::ZOOM>
33 turn is a thin layer on top of the ZOOM-C code supplied as part of
34 Index Data's YAZ Toolkit. Because ZOOM-C is also the underlying code
35 that implements ZOOM bindings in C++, Visual Basic, Scheme, Ruby, .NET
36 (including C#) and other languages, this Perl module works compatibly
37 with those other implementations. (Of course, the point of a public
38 API such as ZOOM is that all implementations should be compatible
39 anyway; but knowing that the same code is running is reassuring.)
41 The ZOOM module provides two enumerations (C<ZOOM::Error> and
42 C<ZOOM::Event>), two utility functions C<diag_str()> and C<event()> in
43 the C<ZOOM> package itself, and eight classes:
53 Of these, the Query class is abstract, and has three concrete
58 C<ZOOM::Query::CQL2RPN>.
59 Finally, it also provides a
61 module which supplies a useful general-purpose logging facility.
62 Many useful ZOOM applications can be built using only the Connection,
63 ResultSet, Record and Exception classes, as in the example
66 A typical application will begin by creating an Connection object,
67 then using that to execute searches that yield ResultSet objects, then
68 fetching records from the result-sets to yield Record objects. If an
69 error occurs, an Exception object is thrown and can be dealt with.
71 More sophisticated applications might also browse the server's indexes
72 to create a ScanSet, from which indexed terms may be retrieved; others
73 might send ``Extended Services'' Packages to the server, to achieve
74 non-standard tasks such as database creation and record update.
75 Searching using a query syntax other than PQF can be done using an
76 query object of one of the Query subclasses. Finally, sets of options
77 may be manipulated independently of the objects they are associated
78 with using an Options object.
80 In general, method calls throw an exception if anything goes wrong, so
81 you don't need to test for success after each call. See the section
82 below on the Exception class for details.
84 =head1 UTILITY FUNCTIONS
86 =head2 ZOOM::diag_str()
88 $msg = ZOOM::diag_str(ZOOM::Error::INVALID_QUERY);
90 Returns a human-readable English-language string corresponding to the
91 error code that is its own parameter. This works for any error-code
93 C<ZOOM::Exception::code()>,
94 C<ZOOM::Connection::error_x()>
96 C<ZOOM::Connection::errcode()>,
97 irrespective of whether it is a member of the C<ZOOM::Error>
98 enumeration or drawn from the BIB-1 diagnostic set.
102 $connsRef = [ $conn1, $conn2, $conn3 ];
103 $which = ZOOM::event($connsRef);
104 $ev = $connsRef->[$which-1]->last_event()
107 Used only in complex asynchronous applications, this function takes a
108 reference to a list of Connection objects, waits until an event
109 occurs on any one of them, and returns an integer indicating which of
110 the connections it occurred on. The return value is a 1-based index
111 into the list; 0 is returned if no event occurs within the longest
112 timeout specified by the C<timeout> options of all the connections.
114 See the section below on asynchronous applications.
118 The eight ZOOM classes are described here in ``sensible order'':
119 first, the four commonly used classes, in the he order that they will
120 tend to be used in most programs (Connection, ResultSet, Record,
121 Exception); then the four more esoteric classes in descending order of
122 how often they are needed.
124 With the exception of the Options class, which is an extension to the
125 ZOOM model, the introduction to each class includes a link to the
126 relevant section of the ZOOM Abstract API.
128 =head2 ZOOM::Connection
130 $conn = new ZOOM::Connection("indexdata.dk:210/gils");
131 print("server is '", $conn->option("serverImplementationName"), "'\n");
132 $conn->option(preferredRecordSyntax => "usmarc");
133 $rs = $conn->search_pqf('@attr 1=4 mineral');
134 $ss = $conn->scan('@attr 1=1003 a');
135 if ($conn->errcode() != 0) {
136 die("somthing went wrong: " . $conn->errmsg())
140 This class represents a connection to an information retrieval server,
141 using an IR protocol such as ANSI/NISO Z39.50, SRW (the
142 Search/Retrieve Webservice), SRU (the Search/Retrieve URL) or
143 OpenSearch. Not all of these protocols require a low-level connection
144 to be maintained, but the Connection object nevertheless provides a
145 location for the necessary cache of configuration and state
146 information, as well as a uniform API to the connection-oriented
147 facilities (searching, index browsing, etc.), provided by these
150 See the description of the C<Connection> class in the ZOOM Abstract
152 http://zoom.z3950.org/api/zoom-current.html#3.2
158 $conn = new ZOOM::Connection("indexdata.dk", 210);
159 $conn = new ZOOM::Connection("indexdata.dk:210/gils");
160 $conn = new ZOOM::Connection("tcp:indexdata.dk:210/gils");
161 $conn = new ZOOM::Connection("http:indexdata.dk:210/gils");
162 $conn = new ZOOM::Connection("indexdata.dk", 210,
163 databaseName => "mydb",
164 preferredRecordSyntax => "marc");
166 Creates a new Connection object, and immediately connects it to the
167 specified server. If you want to make a new Connection object but
168 delay forging the connection, use the C<create()> and C<connect()>
171 This constructor can be called with two arguments or a single
172 argument. In the former case, the arguments are the name and port
173 number of the Z39.50 server to connect to; in the latter case, the
174 single argument is a YAZ service-specifier string of the form
176 When the two-option form is used (which may be done using a vacuous
177 second argument of zero), any number of additional argument pairs may
178 be provided, which are interpreted as key-value pairs to be set as
179 options after the Connection object is created but before it is
180 connected to the server. This is a convenient way to set options,
181 including those that must be set before connecting such as
182 authentication tokens.
188 [I<scheme>:]I<host>[:I<port>][/I<databaseName>]
192 In which the I<host> and I<port> parts are as in the two-argument
193 form, the I<databaseName> if provided specifies the name of the
194 database to be used in subsequent searches on this connection, and the
195 optional I<scheme> (default C<tcp>) indicates what protocol should be
196 used. At present, the following schemes are supported:
206 Z39.50 connection encrypted using SSL (Secure Sockets Layer). Not
207 many servers support this, but Index Data's Zebra is one that does.
211 Z39.50 connection on a Unix-domain (local) socket, in which case the
212 I<hostname> portion of the string is instead used as a filename in the
217 SRW connection using SOAP over HTTP.
221 Support for SRU will follow in the fullness of time.
223 If an error occurs, an exception is thrown. This may indicate a
224 networking problem (e.g. the host is not found or unreachable), or a
225 protocol-level problem (e.g. a Z39.50 server rejected the Init
228 =head4 create() / connect()
230 $options = new ZOOM::Options();
231 $options->option(implementationName => "my client");
232 $conn = create ZOOM::Connection($options)
233 $conn->connect($host, 0);
235 The usual Connection constructor, C<new()> brings a new object into
236 existence and forges the connection to the server all in one
237 operation, which is often what you want. For applications that need
238 more control, however, these two method separate the two steps,
239 allowing additional steps in between such as the setting of options.
241 C<create()> creates and returns a new Connection object, which is
242 I<not> connected to any server. It may be passed an options block, of
243 type C<ZOOM::Options> (see below), into which options may be set
244 before or after the creation of the Connection. The connection to the
245 server may then be forged by the C<connect()> method, the arguments of
246 which are the same as those of the C<new()> constructor.
248 =head4 error_x() / errcode() / errmsg() / addinfo() / diagset()
250 ($errcode, $errmsg, $addinfo, $diagset) = $conn->error_x();
251 $errcode = $conn->errcode();
252 $errmsg = $conn->errmsg();
253 $addinfo = $conn->addinfo();
254 $diagset = $conn->diagset();
256 These methods may be used to obtain information about the last error
257 to have occurred on a connection - although typically they will not
258 been used, as the same information is available through the
259 C<ZOOM::Exception> that is thrown when the error occurs. The
265 methods each return one element of the diagnostic, and
267 returns all four at once.
269 See the C<ZOOM::Exception> for the interpretation of these elements.
271 =head4 option() / option_binary()
273 print("server is '", $conn->option("serverImplementationName"), "'\n");
274 $conn->option(preferredRecordSyntax => "usmarc");
275 $conn->option_binary(iconBlob => "foo\0bar");
276 die if length($conn->option_binary("iconBlob") != 7);
278 Objects of the Connection, ResultSet, ScanSet and Package classes
279 carry with them a set of named options which affect their behaviour in
280 certain ways. See the ZOOM-C options documentation for details:
282 Connection options are listed at
283 http://indexdata.com/yaz/doc/zoom.tkl#zoom.connections
285 These options are set and fetched using the C<option()> method, which
286 may be called with either one or two arguments. In the two-argument
287 form, the option named by the first argument is set to the value of
288 the second argument, and its old value is returned. In the
289 one-argument form, the value of the specified option is returned.
291 For historical reasons, option values are not binary-clean, so that a
292 value containing a NUL byte will be returned in truncated form. The
293 C<option_binary()> method behaves identically to C<option()> except
294 that it is binary-clean, so that values containing NUL bytes are set
295 and returned correctly.
297 =head4 search() / search_pqf()
299 $rs = $conn->search(new ZOOM::Query::CQL('title=dinosaur'));
300 # The next two lines are equivalent
301 $rs = $conn->search(new ZOOM::Query::PQF('@attr 1=4 dinosaur'));
302 $rs = $conn->search_pqf('@attr 1=4 dinosaur');
304 The principal purpose of a search-and-retrieve protocol is searching
305 (and, er, retrieval), so the principal method used on a Connection
306 object is C<search()>. It accepts a single argument, a C<ZOOM::Query>
307 object (or, more precisely, an object of a subclass of this class);
308 and it creates and returns a new ResultSet object representing the set
309 of records resulting from the search.
311 Since queries using PQF (Prefix Query Format) are so common, we make
312 them a special case by providing a C<search_pqf()> method. This is
313 identical to C<search()> except that it accepts a string containing
314 the query rather than an object, thereby obviating the need to create
315 a C<ZOOM::Query::PQF> object. See the documentation of that class for
316 information about PQF.
318 =head4 scan() / scan_pqf()
320 $rs = $conn->scan(new ZOOM::Query::CQL('title=dinosaur'));
321 # The next two lines are equivalent
322 $rs = $conn->scan(new ZOOM::Query::PQF('@attr 1=4 dinosaur'));
323 $rs = $conn->scan_pqf('@attr 1=4 dinosaur');
325 Many Z39.50 servers allow you to browse their indexes to find terms to
326 search for. This is done using the C<scan> method, which creates and
327 returns a new ScanSet object representing the set of terms resulting
330 C<scan()> takes a single argument, but it has to work hard: it
331 specifies both what index to scan for terms, and where in the index to
332 start scanning. What's more, the specification of what index to scan
333 includes multiple facets, such as what database fields it's an index
334 of (author, subject, title, etc.) and whether to scan for whole fields
335 or single words (e.g. the title ``I<The Empire Strikes Back>'', or the
336 four words ``Back'', ``Empire'', ``Strikes'' and ``The'', interleaved
337 with words from other titles in the same index.
339 All of this is done by using a Query object representing a query of a
340 single term as the C<scan()> argument. The attributes associated with
341 the term indicate which index is to be used, and the term itself
342 indicates the point in the index at which to start the scan. For
343 example, if the argument is the query C<@attr 1=4 fish>, then
349 This is the BIB-1 attribute with type 1 (meaning access-point, which
350 specifies an index), and type 4 (which means ``title''). So the scan
351 is in the title index.
355 Start the scan from the lexicographically earliest term that is equal
356 to or falls after ``fish''.
360 The argument C<@attr 1=4 @attr 6=3 fish> would behave similarly; but
361 the BIB-1 attribute 6=3 mean completeness=``complete field'', so the
362 scan would be for complete titles rather than for words occurring in
365 This takes a bit of getting used to.
367 The behaviour is C<scan()> is affected by the following options, which
368 may be set on the Connection through which the scan is done:
372 =item number [default: 10]
374 Indicates how many terms should be returned in the ScanSet. The
375 number actually returned may be less, if the start-point is near the
376 end of the index, but will not be greater.
378 =item position [default: 1]
380 A 1-based index specifying where in the returned list of terms the
381 seed-term should appear. By default it should be the first term
382 returned, but C<position> may be set, for example, to zero (requesting
383 the next terms I<after> the seed-term), or to the same value as
384 C<number> (requesting the index terms I<before> the seed term).
386 =item stepSize [default: 0]
388 An integer indicating how many indexed terms are to be skipped between
389 each one returned in the ScanSet. By default, no terms are skipped,
390 but overriding this can be useful to get a high-level overview of the
393 Since scans using PQF (Prefix Query Format) are so common, we make
394 them a special case by providing a C<scan_pqf()> method. This is
395 identical to C<scan()> except that it accepts a string containing the
396 query rather than an object, thereby obviating the need to create a
397 C<ZOOM::Query::PQF> object.
403 $p = $conn->package();
404 $o = new ZOOM::Options();
405 $o->option(databaseName => "newdb");
406 $p = $conn->package($o);
408 Creates and returns a new C<ZOOM::Package>, to be used in invoking an
409 Extended Service. An options block may optionally be passed in. See
410 the C<ZOOM::Package> documentation.
414 if ($conn->last_event() == ZOOM::Event::CONNECT) {
415 print "Connected!\n";
418 Returns a C<ZOOM::Event> enumerated value indicating the type of the
419 last event that occurred on the connection. This is used only in
420 complex asynchronous applications - see the sections below on the
421 C<ZOOM::Event> enumeration and asynchronous applications.
427 Destroys a Connection object, tearing down any low-level connection
428 associated with it and freeing its resources. It is an error to reuse
429 a Connection that has been C<destroy()>ed.
431 =head2 ZOOM::ResultSet
433 $rs = $conn->search_pqf('@attr 1=4 mineral');
436 $rec = $rs->record($i-1);
437 print $rec->render();
440 A ResultSet object represents the set of zero or more records
441 resulting from a search, and is the means whereby these records can be
442 retrieved. A ResultSet object may maintain client side cache or some,
443 less, none, all or more of the server's records: in general, this is
444 supposed to an implementaton detail of no interest to a typical
445 application, although more sophisticated applications do have
446 facilities for messing with the cache. Most applications will only
447 need the C<size()>, C<record()> and C<sort()> methods.
449 There is no C<new()> method nor any other explicit constructor. The
450 only way to create a new ResultSet is by using C<search()> (or
451 C<search_pqf()>) on a Connection.
453 See the description of the C<Result Set> class in the ZOOM Abstract
455 http://zoom.z3950.org/api/zoom-current.html#3.4
461 $rs->option(elementSetName => "f");
463 Allows options to be set into, and read from, a ResultSet, just like
464 the Connection class's C<option()> method. There is no
465 C<option_binary()> method for ResultSet objects.
467 ResultSet options are listed at
468 http://indexdata.com/yaz/doc/zoom.resultsets.tkl
472 print "Found ", $rs->size(), " records\n";
474 Returns the number of records in the result set.
476 =head4 record() / record_immediate()
478 $rec = $rs->record(0);
479 $rec2 = $rs->record_immediate(0);
480 $rec3 = $rs->record_immediate(1)
481 or print "second record wasn't in cache\n";
483 The C<record()> method returns a C<ZOOM::Record> object representing
484 a record from result-set, whose position is indicated by the argument
485 passed in. This is a zero-based index, so that legitimate values
486 range from zero to C<$rs->size()-1>.
488 The C<record_immediate()> API is identical, but it never invokes a
489 network operation, merely returning the record from the ResultSet's
490 cache if it's already there, or an undefined value otherwise. So if
491 you use this method, B<you must always check the return value>.
495 $rs->records(0, 10, 0);
497 print $rs->record_immediate($i)->render();
500 @nextseven = $rs->records(10, 7, 1);
502 The C<record_immediate()> method only fetches records from the cache,
503 whereas C<record()> fetches them from the server if they have not
504 already been cached; but the ZOOM module has to guess what the most
505 efficient strategy for this is. It might fetch each record, alone
506 when asked for: that's optimal in an application that's only
507 interested in the top hit from each search, but pessimal for one that
508 wants to display a whole list of results. Conversely, the software's
509 strategy might be always to ask for blocks of a twenty records:
510 that's great for assembling long lists of things, but wasteful when
511 only one record is wanted. The problem is that the ZOOM module can't
512 tell, when you call C<$rs->record()>, what your intention is.
514 But you can tell it. The C<records()> method fetches a sequence of
515 records, all in one go. It takes three arguments: the first is the
516 zero-based index of the first record in the sequence, the second is
517 the number of records to fetch, and the third is a boolean indication
518 of whether or not to return the retrieved records as well as adding
519 them to the cache. (You can always pass 1 for this if you like, and
520 Perl will discard the unused return value, but there is a small
521 efficiency gain to be had by passing 0.)
523 Once the records have been retrieved from the server
524 (i.e. C<records()> has completed without throwing an exception), they
525 can be fetched much more efficiently using C<record()> - or
526 C<record_immediate()>, which is then guaranteed to succeed.
532 Resets the ResultSet's record cache, so that subsequent invocations of
533 C<record_immediate()> will fail. I struggle to imagine a real
534 scenario where you'd want to do this.
538 if ($rs->sort("yaz", "1=4 >i 1=21 >s") < 0) {
542 Sorts the ResultSet in place (discarding any cached records, as they
543 will in general be sorted into a different position). There are two
544 arguments: the first is a string indicating the type of the
545 sort-specification, and the second is the specification itself.
547 The C<sort()> method returns 0 on success, or -1 if the
548 sort-specification is invalid.
550 At present, the only supported sort-specification type is C<yaz>.
551 Such a specification consists of a space-separated sequence of keys,
552 each of which itself consists of two space-separated words (so that
553 the total number of words in the sort-specification is even). The two
554 words making up each key are a field and a set of flags. The field
555 can take one of two forms: if it contains an C<=> sign, then it is a
556 BIB-1 I<type>=I<value> pair specifying which field to sort
557 (e.g. C<1=4> for a title sort); otherwise it is sent for the server to
558 interpret as best it can. The word of flags is made up from one or
559 more of the following: C<s> for case sensitive, C<i> for case
560 insensitive; C<<> for ascending order and C<E<gt>> for descending
563 For example, the sort-specification in the code-fragment above will
564 sort the records in C<$rs> case-insensitively in descending order of
565 title, with records having equivalent titles sorted case-sensitively
566 in ascending order of subject. (The BIB-1 access points 4 and 21
567 represent title and subject respectively.)
573 Destroys a ResultSet object, freeing its resources. It is an error to
574 reuse a ResultSet that has been C<destroy()>ed.
578 $rec = $rs->record($i);
579 print $rec->render();
581 $marc = new_from_usmarc MARC::Record($raw);
582 print "Record title is: ", $marc->title(), "\n";
584 A Record object represents a record that has been retrived from the
587 There is no C<new()> method nor any other explicit constructor. The
588 only way to create a new Record is by using C<record()> (or
589 C<record_immediate()>, or C<records()>) on a ResultSet.
591 In general, records are ``owned'' by their result-sets that they were
592 retrieved from, so they do not have to be explicitly memory-managed:
593 they are deallocated (and therefore can no longer be used) when the
594 result-set is destroyed.
596 See the description of the C<Record> class in the ZOOM Abstract
598 http://zoom.z3950.org/api/zoom-current.html#3.5
604 print $rec->render();
605 print $rec->render("charset=latin1,utf8");
607 Returns a human-readable representation of the record. Beyond that,
608 no promises are made: careful programs should not make assumptions
609 about the format of the returned string.
611 If the optional argument is provided, then it is interpreted as in the
612 C<get()> method (q.v.)
614 This method is useful mostly for debugging.
620 $marc = new_from_usmarc MARC::Record($raw);
621 $trans = $rec->render("charset=latin1,utf8");
623 Returns an opaque blob of data that is the raw form of the record.
624 Exactly what this is, and what you can do with it, varies depending on
625 the record-syntax. For example, XML records will be returned as,
626 well, XML; MARC records will be returned as ISO 2709-encoded blocks
627 that can be decoded by software such as the fine C<Marc::Record>
628 module; GRS-1 record will be ... gosh, what an interesting question.
629 But no-one uses GRS-1 any more, do they?
631 If the optional argument is provided, then it is interpreted as in the
632 C<get()> method (q.v.)
636 $raw = $rec->get("raw");
637 $rendered = $rec->get("render");
638 $trans = $rec->get("render;charset=latin1,utf8");
639 $trans = $rec->get("render", "charset=latin1,utf8");
641 This is the underlying method used by C<render()> and C<raw()>, and
642 which in turn delegates to the C<ZOOM_record_get()> function of the
643 underlying ZOOM-C library. Most applications will find it more
644 natural to work with C<render()> and C<raw()>.
646 C<get()> may be called with either one or two arguments. The
647 two-argument form is syntactic sugar: the two arguments are simply
648 joined with a semi-colon to make a single argument, so the third and
649 fourth example invocations above are equivalent. The second argument
650 (or portion of the first argument following the semicolon) is used in
651 the C<type> argument of C<ZOOM_record_get()>, as described in
652 http://www.indexdata.com/yaz/doc/zoom.records.tkl
653 This is useful primarily for invoking the character-set transformation
654 - in the examples above, from ISO Latin-1 to UTF-8 Unicode.
656 =head4 clone() / destroy()
658 $rec = $rs->record($i);
659 $newrec = $rec->clone();
661 print $newrec->render();
664 Usually, it's convenient that Record objects are owned by their
665 ResultSets and go away when the ResultSet is destroyed; but
666 occasionally you need a Record to outlive its parent and destroy it
667 later, explicitly. To do this, C<clone()> the record, keep the new
668 Record object that is returned, and C<destroy()> it when it's no
669 longer needed. This is B<only> situation in which a Record needs to
672 =head2 ZOOM::Exception
674 In general, method calls throw an exception (of class
675 C<ZOOM::Exception>) if anything goes wrong, so you don't need to test
676 for success after each call. Exceptions are caught by enclosing the
677 main code in an C<eval{}> block and checking C<$@> on exit from that
678 block, as in the code-sample above.
680 There are a small number of exceptions to this rule: the three
681 record-fetching methods in the C<ZOOM::ResultSet> class,
683 C<record_immediate()>,
686 can all return undefined values for legitimate reasons, under
687 circumstances that do not merit throwing an exception. For this
688 reason, the return values of these methods should be checked. See the
689 individual methods' documentation for details.
691 An exception carries the following pieces of information:
697 A numeric code that specifies the type of error. This can be checked
698 for equality with known values, so that intelligent applications can
699 take appropriate action.
703 A human-readable message corresponding with the code. This can be
704 shown to users, but its value should not be tested, as it could vary
705 in different versions or under different locales.
707 =item additional information [optional]
709 A string containing information specific to the error-code. For
710 example, when the error-code is the BIB-1 diagnostic 109 ("Database
711 unavailable"), the additional information is the name of the database
712 that the application tried to use. For some error-codes, there is no
713 additional information at all; for some others, the additional
714 information is undefined and may just be an human-readable string.
716 =item diagnostic set [optional]
718 A short string specifying the diagnostic set from which the error-code
719 was drawn: for example, C<ZOOM> for a ZOOM-specific error such as
720 C<ZOOM::Error::MEMORY> ("out of memory"), and C<BIB-1> for a Z39.50
721 error-code drawn from the BIB-1 diagnostic set.
725 In theory, the error-code should be interpreted in the context of the
726 diagnostic set from which it is drawn; in practice, nearly all errors
727 are from either the ZOOM or BIB-1 diagnostic sets, and the codes in
728 those sets have been chosen so as not to overlap, so the diagnostic
729 set can usually be ignored.
731 See the description of the C<Exception> class in the ZOOM Abstract
733 http://zoom.z3950.org/api/zoom-current.html#3.7
739 die new ZOOM::Exception($errcode, $errmsg, $addinfo, $diagset);
741 Creates and returns a new Exception object with the specified
742 error-code, error-message, additional information and diagnostic set.
743 Applications will not in general need to use this, but may find it
744 useful to simulate ZOOM exceptions. As is usual with Perl, exceptions
745 are thrown using C<die()>.
747 =head4 code() / message() / addinfo() / diagset()
749 print "Error ", $@->code(), ": ", $@->message(), "\n";
750 print "(addinfo '", $@->addinfo(), "', set '", $@->diagset(), "')\n";
752 These methods, of no arguments, return the exception's error-code,
753 error-message, additional information and diagnostic set respectively.
759 Returns a human-readable rendition of an exception. The C<"">
760 operator is overloaded on the Exception class, so that an Exception
761 used in a string context is automatically rendered. Among other
762 consequences, this has the useful result that a ZOOM application that
763 died due to an uncaught exception will emit an informative message
768 $ss = $conn->scan('@attr 1=1003 a');
770 ($term, $occ) = $ss->term($n-1);
771 $rs = $conn->search_pqf('@attr 1=1003 "' . $term . "'");
772 assert($rs->size() == $occ);
774 A ScanSet represents a set of candidate search-terms returned from an
775 index scan. Its sole purpose is to provide access to those term, to
776 the corresponding display terms, and to the occurrence-counts of the
779 There is no C<new()> method nor any other explicit constructor. The
780 only way to create a new ScanSet is by using C<scan()> on a
783 See the description of the C<Scan Set> class in the ZOOM Abstract
785 http://zoom.z3950.org/api/zoom-current.html#3.6
791 print "Found ", $ss->size(), " terms\n";
793 Returns the number of terms in the scan set. In general, this will be
794 the scan-set size requested by the C<number> option in the Connection
795 on which the scan was performed [default 10], but it may be fewer if
796 the scan is close to the end of the index.
798 =head4 term() / display_term()
800 $ss = $conn->scan('@attr 1=1004 whatever');
801 ($term, $occurrences) = $ss->term(0);
802 ($displayTerm, $occurrences2) = $ss->display_term(0);
803 assert($occurrences == $occurrences2);
804 if (user_likes_the_look_of($displayTerm)) {
805 $rs = $conn->search_pqf('@attr 1=4 "' . $term . '"');
806 assert($rs->size() == $occurrences);
809 These methods return the scanned terms themselves. C<term()> returns
810 the term is a form suitable for submitting as part of a query, whereas
811 C<display_term()> returns it in a form suitable for displaying to a
812 user. Both versions also return the number of occurrences of the term
813 in the index, i.e. the number of hits that will be found if the term
814 is subsequently used in a query.
816 In most cases, the term and display term will be identical; however,
817 they may be different in cases where punctuation or case is
818 normalised, or where identifiers rather than the original document
823 print "scan status is ", $ss->option("scanStatus");
825 Allows options to be set into, and read from, a ScanSet, just like
826 the Connection class's C<option()> method. There is no
827 C<option_binary()> method for ScanSet objects.
829 ScanSet options are also described, though not particularly
831 http://indexdata.com/yaz/doc/zoom.scan.tkl
837 Destroys a ScanSet object, freeing its resources. It is an error to
838 reuse a ScanSet that has been C<destroy()>ed.
842 $p = $conn->package();
843 $p->option(action => "specialUpdate");
844 $p->option(recordIdOpaque => 145);
845 $p->option(record => content_of("/tmp/record.xml"));
849 This class represents an Extended Services Package: an instruction to
850 the server to do something not covered by the core parts of the Z39.50
851 standard (or the equivalent in SRW or SRU). Since the core protocols
852 are read-only, such requests are often used to make changes to the
853 database, such as in the record update example above.
855 Requesting an extended service is a four-step process: first, create a
856 package associated with the connection to the relevant database;
857 second, set options on the package to instruct the server on what to
858 do; third, send the package (which may result in an exception being
859 thrown if the server cannot execute the requested operations; and
860 finally, destroy the package.
862 Package options are listed at
863 http://indexdata.com/yaz/doc/zoom.ext.tkl
865 The particular options that have meaning are determined by the
866 top-level operation string specified as the argument to C<send()>.
867 For example, when the operation is C<update> (the most commonly used
868 extended service), the C<action> option may be set to any of
870 (add a new record, failing if that record already exists),
872 (delete a record, failing if it is not in the database).
874 (replace a record, failing if an old version is not already present)
877 (add a record, replacing any existing version that may be present).
879 For update, the C<record> option should be set to the full text of the
880 XML record to added, deleted or replaced. Depending on how the server
881 is configured, it may extract the record's unique ID from the text
882 (i.e. from a known element such as the C<001> field of a MARCXML
883 record), or it may require the unique ID to passed in explicitly using
884 the C<recordIdOpaque> option.
886 Extended services packages are B<not currently described> in the ZOOM
888 http://zoom.z3950.org/api/zoom-current.html
889 They will be added in a forthcoming version, and will function much
890 as those implemented in this module.
896 $p->option(recordIdOpaque => "46696f6e61");
898 Allows options to be set into, and read from, a Package, just like
899 the Connection class's C<option()> method. There is no
900 C<option_binary()> method for Package objects.
902 Package options are listed at
903 http://indexdata.com/yaz/doc/zoom.ext.tkl
909 Sends a package to the server associated with the Connection that
910 created it. Problems are reported by throwing an exception. The
911 single parameter indicates the operation that the server is being
912 requested to perform, and controls the interpretation of the package's
913 options. Valid operations include:
919 Request a copy of a nominated object, e.g. place an ILL request.
923 Create a new database, the name of which is specified by the
924 C<databaseName> option.
928 Drop an existing database, the name of which is specified by the
929 C<databaseName> option.
933 Commit changes made to the database within a transaction.
937 Modify the contents of the database by adding, deleting or replacing
938 records (as described above in the overview of the C<ZOOM::Package>
943 I have no idea what this does.
947 Although the module is capable of I<making> all these requests, not
948 all servers are capable of I<executing> them. Refusal is indicated by
949 throwing an exception. Problems may also be caused by lack of
950 privileges; so C<send()> must be used with caution, and is perhaps
951 best wrapped in a clause that checks for execptions, like so:
953 eval { $p->send("create") };
954 if ($@ && $@->isa("ZOOM::Exception")) {
955 print "Oops! ", $@->message(), "\n";
963 Destroys a Package object, freeing its resources. It is an error to
964 reuse a Package that has been C<destroy()>ed.
968 $q = new ZOOM::Query::CQL("creator=pike and subject=unix");
969 $q->sortby("1=4 >i 1=21 >s");
970 $rs = $conn->search($q);
973 C<ZOOM::Query> is a virtual base class from which various concrete
974 subclasses can be derived. Different subclasses implement different
975 types of query. The sole purpose of a Query object is to be used in a
976 C<search()> on a Connection; because PQF is such a common special
977 case, the shortcut Connection method C<search_pqf()> is provided.
979 The following Query subclasses are provided, each providing the
980 same set of methods described below:
984 =item ZOOM::Query::PQF
986 Implements Prefix Query Format (PQF), also sometimes known as Prefix
987 Query Notation (PQN). This esoteric but rigorous and expressive
988 format is described in the YAZ Manual at
989 http://indexdata.com/yaz/doc/tools.tkl#PQF
991 =item ZOOM::Query::CQL
993 Implements the Common Query Language (CQL) of SRU, the Search/Retrieve
994 URL. CQL is a much friendlier notation than PQF, using a simple infix
995 notation. The queries are passed ``as is'' to the server rather than
996 being compiled into a Z39.50 Type-1 query, so only CQL-compliant
997 servers can support such querier. CQL is described at
998 http://www.loc.gov/standards/sru/cql/
999 and in a slight out-of-date but nevertheless useful tutorial at
1000 http://zing.z3950.org/cql/intro.html
1002 =item ZOOM::Query::CQL2RPN
1004 Implements CQL by compiling it on the client-side into a Z39.50
1005 Type-1 (RPN) query, and sending that. This provides essentially the
1006 same functionality as C<ZOOM::Query::CQL>, but it will work against
1007 any standard Z39.50 server rather than only against the small subset
1008 that support CQL natively. The drawback is that, because the
1009 compilation is done on the client side, a configuration file is
1010 required to direct the mapping of CQL constructs such as index names,
1011 relations and modifiers into Type-1 query attributes. An example CQL
1012 configuration file is included in the ZOOM-Perl distribution, in the
1013 file C<samples/cql/pqf.properties>
1017 See the description of the C<Query> class in the ZOOM Abstract
1019 http://zoom.z3950.org/api/zoom-current.html#3.3
1025 $q = new ZOOM::Query::CQL('title=dinosaur');
1026 $q = new ZOOM::Query::PQF('@attr 1=4 dinosaur');
1028 Creates a new query object, compiling the query passed as its argument
1029 according to the rules of the particular query-type being
1030 instantiated. If compilation fails, an exception is thrown.
1031 Otherwise, the query may be passed to the C<Connection> method
1034 $conn->option(cqlfile => "samples/cql/pqf.properties");
1035 $q = new ZOOM::Query::CQL2RPN('title=dinosaur', $conn);
1037 Note that for the C<ZOOM::Query::CQL2RPN> subclass, the Connection
1038 must also be passed into the constructor. This is used for two
1039 purposes: first, its C<cqlfile> option is used to find the CQL
1040 configuration file that directs the translations into RPN; and second,
1041 if compilation fails, then diagnostic information is cached in the
1042 Connection and be retrieved using C<$conn-E<gt>errcode()> and related
1047 $q->sortby("1=4 >i 1=21 >s");
1049 Sets a sort specification into the query, so that when a C<search()>
1050 is run on the query, the result is automatically sorted. The sort
1051 specification language is the same as the C<yaz> sort-specification
1052 type of the C<ResultSet> method C<sort()>, described above.
1058 Destroys a Query object, freeing its resources. It is an error to
1059 reuse a Query that has been C<destroy()>ed.
1061 =head2 ZOOM::Options
1063 $o1 = new ZOOM::Options();
1064 $o1->option(user => "alf");
1065 $o2 = new ZOOM::Options();
1066 $o2->option(password => "fruit");
1067 $opts = new ZOOM::Options($o1, $o2);
1068 $conn = create ZOOM::Connection($opts);
1069 $conn->connect($host); # Uses the specified username and password
1071 Several classes of ZOOM objects carry their own sets of options, which
1072 can be manipulated using their C<option()> method. Sometimes,
1073 however, it's useful to deal with the option sets directly, and the
1074 C<ZOOM::Options> class exists to enable this approach.
1076 Option sets are B<not currently described> in the ZOOM
1078 http://zoom.z3950.org/api/zoom-current.html
1079 They are an extension to that specification.
1085 $o1 = new ZOOM::Options();
1086 $o1and2 = new ZOOM::Options($o1);
1087 $o3 = new ZOOM::Options();
1088 $o1and3and4 = new ZOOM::Options($o1, $o3);
1090 Creates and returns a new option set. One or two (but no more)
1091 existing option sets may be passed as arguments, in which case they
1092 become ``parents'' of the new set, which thereby ``inherits'' their
1093 options, the values of the first parent overriding those of the second
1094 when both have a value for the same key. An option set that inherits
1095 from a parent that has its own parents also inherits the grandparent's
1098 =head4 option() / option_binary()
1100 $o->option(preferredRecordSyntax => "usmarc");
1101 $o->option_binary(iconBlob => "foo\0bar");
1102 die if length($o->option_binary("iconBlob") != 7);
1104 These methods are used to get and set options within a set, and behave
1105 the same way as the same-named C<Connection> methods - see above. As
1106 with the C<Connection> methods, values passed to and retrieved using
1107 C<option()> are interpreted as NUL-terminated, while those passed to
1108 and retrieved from C<option_binary()> are binary-clean.
1112 $o->option(x => "T");
1113 $o->option(y => "F");
1114 assert($o->bool("x", 1));
1115 assert(!$o->bool("y", 1));
1116 assert($o->bool("z", 1));
1118 The first argument is a key, and the second is a default value.
1119 Returns the value associated with the specified key as a boolean, or
1120 the default value if the key has not been set. The values C<T> (upper
1121 case) and C<1> are considered true; all other values (including C<t>
1122 (lower case) and non-zero integers other than one) are considered
1125 This method is provided in ZOOM-C because in a statically typed
1126 language it's convenient to have the result returned as an
1127 easy-to-test type. In a dynamically typed language such as Perl, this
1128 problem doesn't arise, so C<bool()> is nearly useless; but it is made
1129 available in case applications need to duplicate the idiosyncratic
1130 interpretation of truth and falsehood and ZOOM-C uses.
1134 $o->option(x => "012");
1135 assert($o->int("x", 20) == 12);
1136 assert($o->int("y", 20) == 20);
1138 Returns the value associated with the specified key as an integer, or
1139 the default value if the key has not been set. See the description of
1140 C<bool()> for why you almost certainly don't want to use this.
1144 $o->set_int(x => "29");
1146 Sets the value of the specified option as an integer. Of course, Perl
1147 happily converts strings to integers on its own, so you can just use
1148 C<option()> for this, but C<set_int()> is guaranteed to use the same
1149 string-to-integer conversion as ZOOM-C does, which might occasionally
1150 be useful. Though I can't imagine how.
1152 =head4 set_callback()
1156 return "$udata-$key-$udata";
1158 $o->set_callback(\&cb, "xyz");
1159 assert($o->option("foo") eq "xyz-foo-xyz");
1161 This method allows a callback function to be installed in an option
1162 set, so that the values of options can be calculated algorithmically
1163 rather than, as usual, looked up in a table. Along with the callback
1164 function itself, an additional datum is provided: when an option is
1165 subsequently looked up, this datum is passed to the callback function
1166 along with the key; and its return value is returned to the caller as
1167 the value of the option.
1170 Although it ought to be possible to specify callback function using
1171 the C<\&name> syntax above, or a literal C<sub { code }> code
1172 reference, the complexities of the Perl-internal memory management
1173 system mean that the function must currently be specified as a string
1174 containing the fully-qualified name, e.g. C<"main::cb">.>
1177 The current implementation of the this method leaks memory, not only
1178 when the callback is installed, but on every occasion that it is
1179 consulted to look up an option value.
1185 Destroys an Options object, freeing its resources. It is an error to
1186 reuse an Options object that has been C<destroy()>ed.
1190 The ZOOM module provides two enumerations that list possible return
1191 values from particular functions. They are described in the following
1196 if ($@->code() == ZOOM::Error::QUERY_PQF) {
1197 return "your query was not accepted";
1200 This class provides a set of manifest constants representing some of
1201 the possible error codes that can be raised by the ZOOM module. The
1202 methods that return error-codes are
1203 C<ZOOM::Exception::code()>,
1204 C<ZOOM::Connection::error_x()>
1206 C<ZOOM::Connection::errcode()>.
1208 The C<ZOOM::Error> class provides the constants
1218 C<UNSUPPORTED_PROTOCOL>,
1219 C<UNSUPPORTED_QUERY>,
1230 each of which specifies a client-side error. These codes constitute
1231 the C<ZOOM> diagnostic set.
1233 Since errors may also be diagnosed by the server, and returned to the
1234 client, error codes may also take values from the BIB-1 diagnostic set
1235 of Z39.50, listed at the Z39.50 Maintenance Agency's web-site at
1236 http://www.loc.gov/z3950/agency/defns/bib1diag.html
1238 All error-codes, whether client-side from the C<ZOOM::Error>
1239 enumeration or server-side from the BIB-1 diagnostic set, can be
1240 translated into human-readable messages by passing them to the
1241 C<ZOOM::diag_str()> utility function.
1245 if ($conn->last_event() == ZOOM::Event::CONNECT) {
1246 print "Connected!\n";
1249 In applications that need it - mostly complex multiplexing
1250 applications - The C<ZOOM::Connection::last_event()> method is used to
1251 return an indication of the last event that occurred on a particular
1252 connection. It always returns a value drawn from this enumeration,
1253 that is, one of C<NONE>, C<CONNECT>, C<SEND_DATA>, C<RECV_DATA>,
1254 C<TIMEOUT>, C<UNKNOWN>, C<SEND_APDU>, C<RECV_APDU>, C<RECV_RECORD>,
1255 C<RECV_SEARCH> or C<ZEND>.
1257 See the section below on asynchronous applications.
1261 ZOOM::Log::init_level(ZOOM::Log::mask_str("zoom,myapp,-warn"));
1262 ZOOM::Log::log("myapp", "starting up with pid ", $$);
1264 Logging facilities are provided by a set of functions in the
1265 C<ZOOM::Log> module. Note that C<ZOOM::Log> is not a class, and it
1266 is not possible to create C<ZOOM::Log> objects: the API is imperative,
1267 reflecting that of the underlying YAZ logging facilities. Although
1268 there are nine logging functions altogether, you can ignore nearly
1269 all of them: most applications that use logging will begin by calling
1270 C<mask_str()> and C<init_level()> once each, as above, and will then
1271 repeatedly call C<log()>.
1275 $level = ZOOM::Log::mask_str("zoom,myapp,-warn");
1277 Returns an integer corresponding to the log-level specified by the
1278 parameter. This is a string of zero or more comma-separated
1279 module-names, each indicating an individual module to be either added
1280 to the default log-level or removed from it (for those components
1281 prefixed by a minus-sign). The names may be those of either standard
1282 YAZ-logging modules such as C<fatal>, C<debug> and C<warn>, or custom
1283 modules such as C<myapp> in the example above. The module C<zoom>
1284 requests logging from the ZOOM module itself, which may be helpful for
1287 Note that calling this function does not in any way change the logging
1288 state: it merely returns a value. To change the state, this value
1289 must be passed to C<init_level()>.
1291 =head2 module_level()
1293 $level = ZOOM::Log::module_level("zoom");
1294 ZOOM::Log::log($level, "all systems clear: thrusters invogriated");
1296 Returns the integer corresponding to the single log-level specified as
1297 the parameter, or zero if that level has not been registered by a
1298 prior call to C<mask_str()>. Since C<log()> accepts either a numeric
1299 log-level or a string, there is no reason to call this function; but,
1300 what the heck, maybe you enjoy that kind of thing. Who are we to
1305 ZOOM::Log::init_level($level);
1307 Initialises the log-level to the specified integer, which is a bitmask
1308 of values, typically as returned from C<mask_str()>. All subsequent
1309 calls to C<log()> made with a log-level that matches one of the bits
1310 in this mask will result in a log-message being emitted. All logging
1311 can be turned off by calling C<init_level(0)>.
1313 =head2 init_prefix()
1315 ZOOM::Log::init_prefix($0);
1317 Initialises a prefix string to be included in all log-messages.
1321 ZOOM::Log::init_file("/tmp/myapp.log");
1323 Initialises the output file to be used for logging: subsequent
1324 log-messages are written to the nominated file. If this function is
1325 not called, log-messages are written to the standard error stream.
1329 ZOOM::Log::init($level, $0, "/tmp/myapp.log");
1331 Initialises the log-level, the logging prefix and the logging output
1332 file in a single operation.
1334 =head2 time_format()
1336 ZOOM::Log::time_format("%Y-%m-%d %H:%M:%S");
1338 Sets the format in which log-messages' timestamps are emitted, by
1339 means of a format-string like that used in the C function
1340 C<strftime()>. The example above emits year, month, day, hours,
1341 minutes and seconds in big-endian order, such that timestamps can be
1342 sorted lexicographically.
1344 =head2 init_max_size()
1346 (This doesn't seem to work, so I won't bother describing it.)
1350 ZOOM::Log::log(8192, "reducing to warp-factor $wf");
1351 ZOOM::Log::log("myapp", "starting up with pid ", $$);
1353 Provided that the first argument, log-level, is among the modules
1354 previously established by C<init_level()>, this function emits a
1355 log-message made up of a timestamp, the prefix supplied to
1356 C<init_prefix()>, if any, and the concatenation of all arguments after
1357 the first. The message is written to the standard output stream, or
1358 to the file previous specified by C<init_file()> if this has been
1361 The log-level argument may be either a numeric value, as returned from
1362 C<module_level()>, or a string containing the module name.
1364 =head1 ASYNCHRONOUS APPLICATIONS
1366 Although asynchronous applications are conceptually complex, the ZOOM
1367 support for them is provided through a very simple interface,
1368 consisting of one option (C<async>), one function (C<ZOOM::event()>),
1369 one Connection method (C<last_event()> and an enumeration
1372 The approach is as follows:
1376 =item Initialisation
1378 Create several connections to the various servers, each of them having
1379 the option C<async> set, and with whatever additional options are
1380 required - e.g. the piggyback retrieval record-count can be set so
1381 that records will be returned in search responses.
1385 Send searches to the connections, request records, etc.
1387 =item Event harvesting
1389 Repeatedly call C<ZOOM::event()> to discover what responses are being
1390 received from the servers. Each time this function returns, it
1391 indicates which of the connections has fired; this connection can then
1392 be interrogated with the C<last_event()> method to discover what event
1393 has occurred, and the return value - an element of the C<ZOOM::Event>
1394 enumeration - can be tested to determine what to do next. For
1395 example, the C<ZEND> event indicates that no further operations are
1396 outstanding on the connection, so any fetched records can now be
1397 immediately obtained.
1401 Here is a very short program (omitting all error-checking!) which
1402 demonstrates this process. It parallel-searches two servers (or more
1403 of you add them the list), displaying the first record in the
1404 result-set of each server as soon as it becomes available.
1407 @servers = ('z3950.loc.gov:7090/Voyager',
1408 'bagel.indexdata.com:210/gils');
1409 for ($i = 0; $i < @servers; $i++) {
1410 $z[$i] = new ZOOM::Connection($servers[$i], 0,
1411 async => 1, # asynchronous mode
1412 count => 1, # piggyback retrieval count
1413 preferredRecordSyntax => "usmarc");
1414 $r[$i] = $z[$i]->search_pqf("mineral");
1416 while (($i = ZOOM::event(\@z)) != 0) {
1417 $ev = $z[$i-1]->last_event();
1418 print("connection ", $i-1, ": ", ZOOM::event_str($ev), "\n");
1419 if ($ev == ZOOM::Event::ZEND) {
1420 $size = $r[$i-1]->size();
1421 print "connection ", $i-1, ": $size hits\n";
1422 print $r[$i-1]->record(0)->render()
1429 The ZOOM abstract API,
1430 http://zoom.z3950.org/api/zoom-current.html
1432 The C<Net::Z3950::ZOOM> module, included in the same distribution as this one.
1434 The C<Net::Z3950> module, which this one supersedes.
1435 http://perl.z3950.org/
1437 The documentation for the ZOOM-C module of the YAZ Toolkit, which this
1438 module is built on. Specifically, its lists of options are useful.
1439 http://indexdata.com/yaz/doc/zoom.tkl
1441 The BIB-1 diagnostic set of Z39.50,
1442 http://www.loc.gov/z3950/agency/defns/bib1diag.html
1446 Mike Taylor, E<lt>mike@indexdata.comE<gt>
1448 =head1 COPYRIGHT AND LICENCE
1450 Copyright (C) 2005 by Index Data.
1452 This library is free software; you can redistribute it and/or modify
1453 it under the same terms as Perl itself, either Perl version 5.8.4 or,
1454 at your option, any later version of Perl 5 you may have available.