1 # $Id: ZOOM.pod,v 1.43 2007-05-09 12:03:52 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>), three utility functions C<diag_str()>, C<event_str()>
43 and C<event()> in the C<ZOOM> package itself, and eight classes:
53 Of these, the Query class is abstract, and has four concrete
57 C<ZOOM::Query::CQL2RPN>
59 C<ZOOM::Query::CCL2RPN>.
60 Finally, it also provides a
62 module which supplies a useful general-purpose logging facility.
63 Many useful ZOOM applications can be built using only the Connection,
64 ResultSet, Record and Exception classes, as in the example
67 A typical application will begin by creating an Connection object,
68 then using that to execute searches that yield ResultSet objects, then
69 fetching records from the result-sets to yield Record objects. If an
70 error occurs, an Exception object is thrown and can be dealt with.
72 More sophisticated applications might also browse the server's indexes
73 to create a ScanSet, from which indexed terms may be retrieved; others
74 might send ``Extended Services'' Packages to the server, to achieve
75 non-standard tasks such as database creation and record update.
76 Searching using a query syntax other than PQF can be done using an
77 query object of one of the Query subclasses. Finally, sets of options
78 may be manipulated independently of the objects they are associated
79 with using an Options object.
81 In general, method calls throw an exception if anything goes wrong, so
82 you don't need to test for success after each call. See the section
83 below on the Exception class for details.
85 =head1 UTILITY FUNCTIONS
87 =head2 ZOOM::diag_str()
89 $msg = ZOOM::diag_str(ZOOM::Error::INVALID_QUERY);
91 Returns a human-readable English-language string corresponding to the
92 error code that is its own parameter. This works for any error-code
94 C<ZOOM::Exception::code()>,
95 C<ZOOM::Connection::error_x()>
97 C<ZOOM::Connection::errcode()>,
98 irrespective of whether it is a member of the C<ZOOM::Error>
99 enumeration or drawn from the BIB-1 diagnostic set.
101 =head2 ZOOM::event_str()
103 $msg = ZOOM::event_str(ZOOM::Event::RECV_APDU);
105 Returns a human-readable English-language string corresponding to the
106 event code that is its own parameter. This works for any value of the
107 C<ZOOM::Event> enumeration.
111 $connsRef = [ $conn1, $conn2, $conn3 ];
112 $which = ZOOM::event($connsRef);
113 $ev = $connsRef->[$which-1]->last_event()
116 Used only in complex asynchronous applications, this function takes a
117 reference to a list of Connection objects, waits until an event
118 occurs on any one of them, and returns an integer indicating which of
119 the connections it occurred on. The return value is a 1-based index
120 into the list; 0 is returned if no event occurs within the longest
121 timeout specified by the C<timeout> options of all the connections.
123 See the section below on asynchronous applications.
127 The eight ZOOM classes are described here in ``sensible order'':
128 first, the four commonly used classes, in the he order that they will
129 tend to be used in most programs (Connection, ResultSet, Record,
130 Exception); then the four more esoteric classes in descending order of
131 how often they are needed.
133 With the exception of the Options class, which is an extension to the
134 ZOOM model, the introduction to each class includes a link to the
135 relevant section of the ZOOM Abstract API.
137 =head2 ZOOM::Connection
139 $conn = new ZOOM::Connection("indexdata.dk:210/gils");
140 print("server is '", $conn->option("serverImplementationName"), "'\n");
141 $conn->option(preferredRecordSyntax => "usmarc");
142 $rs = $conn->search_pqf('@attr 1=4 mineral');
143 $ss = $conn->scan('@attr 1=1003 a');
144 if ($conn->errcode() != 0) {
145 die("somthing went wrong: " . $conn->errmsg())
149 This class represents a connection to an information retrieval server,
150 using an IR protocol such as ANSI/NISO Z39.50, SRW (the
151 Search/Retrieve Webservice), SRU (the Search/Retrieve URL) or
152 OpenSearch. Not all of these protocols require a low-level connection
153 to be maintained, but the Connection object nevertheless provides a
154 location for the necessary cache of configuration and state
155 information, as well as a uniform API to the connection-oriented
156 facilities (searching, index browsing, etc.), provided by these
159 See the description of the C<Connection> class in the ZOOM Abstract
161 http://zoom.z3950.org/api/zoom-current.html#3.2
167 $conn = new ZOOM::Connection("indexdata.dk", 210);
168 $conn = new ZOOM::Connection("indexdata.dk:210/gils");
169 $conn = new ZOOM::Connection("tcp:indexdata.dk:210/gils");
170 $conn = new ZOOM::Connection("http:indexdata.dk:210/gils");
171 $conn = new ZOOM::Connection("indexdata.dk", 210,
172 databaseName => "mydb",
173 preferredRecordSyntax => "marc");
175 Creates a new Connection object, and immediately connects it to the
176 specified server. If you want to make a new Connection object but
177 delay forging the connection, use the C<create()> and C<connect()>
180 This constructor can be called with two arguments or a single
181 argument. In the former case, the arguments are the name and port
182 number of the Z39.50 server to connect to; in the latter case, the
183 single argument is a YAZ service-specifier string of the form
185 When the two-option form is used (which may be done using a vacuous
186 second argument of zero), any number of additional argument pairs may
187 be provided, which are interpreted as key-value pairs to be set as
188 options after the Connection object is created but before it is
189 connected to the server. This is a convenient way to set options,
190 including those that must be set before connecting such as
191 authentication tokens.
193 The server-name string is of the form:
199 [I<scheme>:]I<host>[:I<port>][/I<databaseName>]
203 In which the I<host> and I<port> parts are as in the two-argument
204 form, the I<databaseName> if provided specifies the name of the
205 database to be used in subsequent searches on this connection, and the
206 optional I<scheme> (default C<tcp>) indicates what protocol should be
207 used. At present, the following schemes are supported:
217 Z39.50 connection encrypted using SSL (Secure Sockets Layer). Not
218 many servers support this, but Index Data's Zebra is one that does.
222 Z39.50 connection on a Unix-domain (local) socket, in which case the
223 I<hostname> portion of the string is instead used as a filename in the
228 SRU connection over HTTP.
232 If the C<http> scheme is used, the particular SRU flavour to be used
233 may be specified by the C<sru> option, which takes the following
240 SRU over SOAP (i.e. what used to be called SRW).
245 "SRU Classic" (i.e. SRU over HTTP GET).
253 If an error occurs, an exception is thrown. This may indicate a
254 networking problem (e.g. the host is not found or unreachable), or a
255 protocol-level problem (e.g. a Z39.50 server rejected the Init
258 =head4 create() / connect()
260 $options = new ZOOM::Options();
261 $options->option(implementationName => "my client");
262 $options->option(implementationId => 12345);
263 $conn = create ZOOM::Connection($options)
265 $conn = create ZOOM::Connection(implementationName => "my client",
266 implementationId => 12345);
268 $conn->connect($host, 0);
270 The usual Connection constructor, C<new()> brings a new object into
271 existence and forges the connection to the server all in one
272 operation, which is often what you want. For applications that need
273 more control, however, these two methods separate the two steps,
274 allowing additional steps in between such as the setting of options.
276 C<create()> creates and returns a new Connection object, which is
277 I<not> connected to any server. It may be passed an options block, of
278 type C<ZOOM::Options> (see below), into which options may be set
279 before or after the creation of the Connection. Alternatively and
280 equivalently, C<create()> may be passed a list of key-value option
281 pairs directly. The connection to the server may then be forged by
282 the C<connect()> method, the arguments of which are the same as those
283 of the C<new()> constructor.
285 =head4 error_x() / errcode() / errmsg() / addinfo() / diagset()
287 ($errcode, $errmsg, $addinfo, $diagset) = $conn->error_x();
288 $errcode = $conn->errcode();
289 $errmsg = $conn->errmsg();
290 $addinfo = $conn->addinfo();
291 $diagset = $conn->diagset();
293 These methods may be used to obtain information about the last error
294 to have occurred on a connection - although typically they will not
295 been used, as the same information is available through the
296 C<ZOOM::Exception> that is thrown when the error occurs. The
302 methods each return one element of the diagnostic, and
304 returns all four at once.
306 See the C<ZOOM::Exception> for the interpretation of these elements.
310 die $conn->exception();
312 C<exception()> returns the same information as C<error_x()> in the
313 form of a C<ZOOM::Exception> object which may be thrown or rendered.
314 If no error occurred on the connection, then C<exception()> returns an
321 Checks whether an error is pending on the connection, and throw a
322 C<ZOOM::Exception> object if so. Since errors are thrown as they
323 occur for synchronous connections, there is no need ever to call this
324 except in asynchronous applications.
326 =head4 option() / option_binary()
328 print("server is '", $conn->option("serverImplementationName"), "'\n");
329 $conn->option(preferredRecordSyntax => "usmarc");
330 $conn->option_binary(iconBlob => "foo\0bar");
331 die if length($conn->option_binary("iconBlob") != 7);
333 Objects of the Connection, ResultSet, ScanSet and Package classes
334 carry with them a set of named options which affect their behaviour in
335 certain ways. See the ZOOM-C options documentation for details:
337 Connection options are listed at
338 http://indexdata.com/yaz/doc/zoom.tkl#zoom.connections
340 These options are set and fetched using the C<option()> method, which
341 may be called with either one or two arguments. In the two-argument
342 form, the option named by the first argument is set to the value of
343 the second argument, and its old value is returned. In the
344 one-argument form, the value of the specified option is returned.
346 For historical reasons, option values are not binary-clean, so that a
347 value containing a NUL byte will be returned in truncated form. The
348 C<option_binary()> method behaves identically to C<option()> except
349 that it is binary-clean, so that values containing NUL bytes are set
350 and returned correctly.
352 =head4 search() / search_pqf()
354 $rs = $conn->search(new ZOOM::Query::CQL('title=dinosaur'));
355 # The next two lines are equivalent
356 $rs = $conn->search(new ZOOM::Query::PQF('@attr 1=4 dinosaur'));
357 $rs = $conn->search_pqf('@attr 1=4 dinosaur');
359 The principal purpose of a search-and-retrieve protocol is searching
360 (and, er, retrieval), so the principal method used on a Connection
361 object is C<search()>. It accepts a single argument, a C<ZOOM::Query>
362 object (or, more precisely, an object of a subclass of this class);
363 and it creates and returns a new ResultSet object representing the set
364 of records resulting from the search.
366 Since queries using PQF (Prefix Query Format) are so common, we make
367 them a special case by providing a C<search_pqf()> method. This is
368 identical to C<search()> except that it accepts a string containing
369 the query rather than an object, thereby obviating the need to create
370 a C<ZOOM::Query::PQF> object. See the documentation of that class for
371 information about PQF.
373 =head4 scan() / scan_pqf()
375 $rs = $conn->scan(new ZOOM::Query::CQL('title=dinosaur'));
376 # The next two lines are equivalent
377 $rs = $conn->scan(new ZOOM::Query::PQF('@attr 1=4 dinosaur'));
378 $rs = $conn->scan_pqf('@attr 1=4 dinosaur');
380 Many Z39.50 servers allow you to browse their indexes to find terms to
381 search for. This is done using the C<scan> method, which creates and
382 returns a new ScanSet object representing the set of terms resulting
385 C<scan()> takes a single argument, but it has to work hard: it
386 specifies both what index to scan for terms, and where in the index to
387 start scanning. What's more, the specification of what index to scan
388 includes multiple facets, such as what database fields it's an index
389 of (author, subject, title, etc.) and whether to scan for whole fields
390 or single words (e.g. the title ``I<The Empire Strikes Back>'', or the
391 four words ``Back'', ``Empire'', ``Strikes'' and ``The'', interleaved
392 with words from other titles in the same index.
394 All of this is done by using a Query object representing a query of a
395 single term as the C<scan()> argument. The attributes associated with
396 the term indicate which index is to be used, and the term itself
397 indicates the point in the index at which to start the scan. For
398 example, if the argument is the query C<@attr 1=4 fish>, then
404 This is the BIB-1 attribute with type 1 (meaning access-point, which
405 specifies an index), and type 4 (which means ``title''). So the scan
406 is in the title index.
410 Start the scan from the lexicographically earliest term that is equal
411 to or falls after ``fish''.
415 The argument C<@attr 1=4 @attr 6=3 fish> would behave similarly; but
416 the BIB-1 attribute 6=3 mean completeness=``complete field'', so the
417 scan would be for complete titles rather than for words occurring in
420 This takes a bit of getting used to.
422 The behaviour is C<scan()> is affected by the following options, which
423 may be set on the Connection through which the scan is done:
427 =item number [default: 10]
429 Indicates how many terms should be returned in the ScanSet. The
430 number actually returned may be less, if the start-point is near the
431 end of the index, but will not be greater.
433 =item position [default: 1]
435 A 1-based index specifying where in the returned list of terms the
436 seed-term should appear. By default it should be the first term
437 returned, but C<position> may be set, for example, to zero (requesting
438 the next terms I<after> the seed-term), or to the same value as
439 C<number> (requesting the index terms I<before> the seed term).
441 =item stepSize [default: 0]
443 An integer indicating how many indexed terms are to be skipped between
444 each one returned in the ScanSet. By default, no terms are skipped,
445 but overriding this can be useful to get a high-level overview of the
448 Since scans using PQF (Prefix Query Format) are so common, we make
449 them a special case by providing a C<scan_pqf()> method. This is
450 identical to C<scan()> except that it accepts a string containing the
451 query rather than an object, thereby obviating the need to create a
452 C<ZOOM::Query::PQF> object.
458 $p = $conn->package();
459 $o = new ZOOM::Options();
460 $o->option(databaseName => "newdb");
461 $p = $conn->package($o);
463 Creates and returns a new C<ZOOM::Package>, to be used in invoking an
464 Extended Service. An options block may optionally be passed in. See
465 the C<ZOOM::Package> documentation.
469 if ($conn->last_event() == ZOOM::Event::CONNECT) {
470 print "Connected!\n";
473 Returns a C<ZOOM::Event> enumerated value indicating the type of the
474 last event that occurred on the connection. This is used only in
475 complex asynchronous applications - see the sections below on the
476 C<ZOOM::Event> enumeration and asynchronous applications.
482 Destroys a Connection object, tearing down any low-level connection
483 associated with it and freeing its resources. It is an error to reuse
484 a Connection that has been C<destroy()>ed.
486 =head2 ZOOM::ResultSet
488 $rs = $conn->search_pqf('@attr 1=4 mineral');
491 $rec = $rs->record($i-1);
492 print $rec->render();
495 A ResultSet object represents the set of zero or more records
496 resulting from a search, and is the means whereby these records can be
497 retrieved. A ResultSet object may maintain client side cache or some,
498 less, none, all or more of the server's records: in general, this is
499 supposed to an implementaton detail of no interest to a typical
500 application, although more sophisticated applications do have
501 facilities for messing with the cache. Most applications will only
502 need the C<size()>, C<record()> and C<sort()> methods.
504 There is no C<new()> method nor any other explicit constructor. The
505 only way to create a new ResultSet is by using C<search()> (or
506 C<search_pqf()>) on a Connection.
508 See the description of the C<Result Set> class in the ZOOM Abstract
510 http://zoom.z3950.org/api/zoom-current.html#3.4
516 $rs->option(elementSetName => "f");
518 Allows options to be set into, and read from, a ResultSet, just like
519 the Connection class's C<option()> method. There is no
520 C<option_binary()> method for ResultSet objects.
522 ResultSet options are listed at
523 http://indexdata.com/yaz/doc/zoom.resultsets.tkl
527 print "Found ", $rs->size(), " records\n";
529 Returns the number of records in the result set.
531 =head4 record() / record_immediate()
533 $rec = $rs->record(0);
534 $rec2 = $rs->record_immediate(0);
535 $rec3 = $rs->record_immediate(1)
536 or print "second record wasn't in cache\n";
538 The C<record()> method returns a C<ZOOM::Record> object representing
539 a record from result-set, whose position is indicated by the argument
540 passed in. This is a zero-based index, so that legitimate values
541 range from zero to C<$rs->size()-1>.
543 The C<record_immediate()> API is identical, but it never invokes a
544 network operation, merely returning the record from the ResultSet's
545 cache if it's already there, or an undefined value otherwise. So if
546 you use this method, B<you must always check the return value>.
550 $rs->records(0, 10, 0);
552 print $rs->record_immediate($i)->render();
555 @nextseven = $rs->records(10, 7, 1);
557 The C<record_immediate()> method only fetches records from the cache,
558 whereas C<record()> fetches them from the server if they have not
559 already been cached; but the ZOOM module has to guess what the most
560 efficient strategy for this is. It might fetch each record, alone
561 when asked for: that's optimal in an application that's only
562 interested in the top hit from each search, but pessimal for one that
563 wants to display a whole list of results. Conversely, the software's
564 strategy might be always to ask for blocks of a twenty records:
565 that's great for assembling long lists of things, but wasteful when
566 only one record is wanted. The problem is that the ZOOM module can't
567 tell, when you call C<$rs->record()>, what your intention is.
569 But you can tell it. The C<records()> method fetches a sequence of
570 records, all in one go. It takes three arguments: the first is the
571 zero-based index of the first record in the sequence, the second is
572 the number of records to fetch, and the third is a boolean indication
573 of whether or not to return the retrieved records as well as adding
574 them to the cache. (You can always pass 1 for this if you like, and
575 Perl will discard the unused return value, but there is a small
576 efficiency gain to be had by passing 0.)
578 Once the records have been retrieved from the server
579 (i.e. C<records()> has completed without throwing an exception), they
580 can be fetched much more efficiently using C<record()> - or
581 C<record_immediate()>, which is then guaranteed to succeed.
587 Resets the ResultSet's record cache, so that subsequent invocations of
588 C<record_immediate()> will fail. I struggle to imagine a real
589 scenario where you'd want to do this.
593 if ($rs->sort("yaz", "1=4 >i 1=21 >s") < 0) {
597 Sorts the ResultSet in place (discarding any cached records, as they
598 will in general be sorted into a different position). There are two
599 arguments: the first is a string indicating the type of the
600 sort-specification, and the second is the specification itself.
602 The C<sort()> method returns 0 on success, or -1 if the
603 sort-specification is invalid.
605 At present, the only supported sort-specification type is C<yaz>.
606 Such a specification consists of a space-separated sequence of keys,
607 each of which itself consists of two space-separated words (so that
608 the total number of words in the sort-specification is even). The two
609 words making up each key are a field and a set of flags. The field
610 can take one of two forms: if it contains an C<=> sign, then it is a
611 BIB-1 I<type>=I<value> pair specifying which field to sort
612 (e.g. C<1=4> for a title sort); otherwise it is sent for the server to
613 interpret as best it can. The word of flags is made up from one or
614 more of the following: C<s> for case sensitive, C<i> for case
615 insensitive; C<<> for ascending order and C<E<gt>> for descending
618 For example, the sort-specification in the code-fragment above will
619 sort the records in C<$rs> case-insensitively in descending order of
620 title, with records having equivalent titles sorted case-sensitively
621 in ascending order of subject. (The BIB-1 access points 4 and 21
622 represent title and subject respectively.)
628 Destroys a ResultSet object, freeing its resources. It is an error to
629 reuse a ResultSet that has been C<destroy()>ed.
633 $rec = $rs->record($i);
634 print $rec->render();
636 $marc = new_from_usmarc MARC::Record($raw);
637 print "Record title is: ", $marc->title(), "\n";
639 A Record object represents a record that has been retrived from the
642 There is no C<new()> method nor any other explicit constructor. The
643 only way to create a new Record is by using C<record()> (or
644 C<record_immediate()>, or C<records()>) on a ResultSet.
646 In general, records are ``owned'' by their result-sets that they were
647 retrieved from, so they do not have to be explicitly memory-managed:
648 they are deallocated (and therefore can no longer be used) when the
649 result-set is destroyed.
651 See the description of the C<Record> class in the ZOOM Abstract
653 http://zoom.z3950.org/api/zoom-current.html#3.5
657 =head4 error() / exception()
660 my($code, $msg, $addinfo, $dset) = $rec->error();
661 print "error $code, $msg ($addinfo) from $dset set\n";
662 die $rec->exception();
665 These functions test for surrogate diagnostics associated with a
666 record: that is, errors pertaining to a particular record rather than
667 to the fetch-some-records operation as a whole. (The latter are known
668 in Z39.50 as non-surrogate diagnostics, and are reported as exceptions
669 thrown by searches.) If a particular record can't be obtained - for
670 example, because it is not available in the requested record syntax -
671 then the record object obtained from the result-set, when interrogated
672 with these functions, will report the error.
674 C<error()> returns the error-code, a human-readable message,
675 additional information and the name of the diagnostic set that the
676 error is from. When called in a scalar context, it just returns the
677 error-code. Since error 0 means "no error", it can be used as a
678 boolean has-there-been-an-error indicator.
680 C<exception()> returns the same information in the form of a
681 C<ZOOM::Exception> object which may be thrown or rendered. If no
682 error occurred on the record, then C<exception()> returns an undefined
687 print $rec->render();
688 print $rec->render("charset=latin1,utf8");
690 Returns a human-readable representation of the record. Beyond that,
691 no promises are made: careful programs should not make assumptions
692 about the format of the returned string.
694 If the optional argument is provided, then it is interpreted as in the
695 C<get()> method (q.v.)
697 This method is useful mostly for debugging.
703 $marc = new_from_usmarc MARC::Record($raw);
704 $trans = $rec->render("charset=latin1,utf8");
706 Returns an opaque blob of data that is the raw form of the record.
707 Exactly what this is, and what you can do with it, varies depending on
708 the record-syntax. For example, XML records will be returned as,
709 well, XML; MARC records will be returned as ISO 2709-encoded blocks
710 that can be decoded by software such as the fine C<Marc::Record>
711 module; GRS-1 record will be ... gosh, what an interesting question.
712 But no-one uses GRS-1 any more, do they?
714 If the optional argument is provided, then it is interpreted as in the
715 C<get()> method (q.v.)
719 $raw = $rec->get("raw");
720 $rendered = $rec->get("render");
721 $trans = $rec->get("render;charset=latin1,utf8");
722 $trans = $rec->get("render", "charset=latin1,utf8");
724 This is the underlying method used by C<render()> and C<raw()>, and
725 which in turn delegates to the C<ZOOM_record_get()> function of the
726 underlying ZOOM-C library. Most applications will find it more
727 natural to work with C<render()> and C<raw()>.
729 C<get()> may be called with either one or two arguments. The
730 two-argument form is syntactic sugar: the two arguments are simply
731 joined with a semi-colon to make a single argument, so the third and
732 fourth example invocations above are equivalent. The second argument
733 (or portion of the first argument following the semicolon) is used in
734 the C<type> argument of C<ZOOM_record_get()>, as described in
735 http://www.indexdata.com/yaz/doc/zoom.records.tkl
736 This is useful primarily for invoking the character-set transformation
737 - in the examples above, from ISO Latin-1 to UTF-8 Unicode.
739 =head4 clone() / destroy()
741 $rec = $rs->record($i);
742 $newrec = $rec->clone();
744 print $newrec->render();
747 Usually, it's convenient that Record objects are owned by their
748 ResultSets and go away when the ResultSet is destroyed; but
749 occasionally you need a Record to outlive its parent and destroy it
750 later, explicitly. To do this, C<clone()> the record, keep the new
751 Record object that is returned, and C<destroy()> it when it's no
752 longer needed. This is B<only> situation in which a Record needs to
755 =head2 ZOOM::Exception
757 In general, method calls throw an exception (of class
758 C<ZOOM::Exception>) if anything goes wrong, so you don't need to test
759 for success after each call. Exceptions are caught by enclosing the
760 main code in an C<eval{}> block and checking C<$@> on exit from that
761 block, as in the code-sample above.
763 There are a small number of exceptions to this rule: the three
764 record-fetching methods in the C<ZOOM::ResultSet> class,
766 C<record_immediate()>,
769 can all return undefined values for legitimate reasons, under
770 circumstances that do not merit throwing an exception. For this
771 reason, the return values of these methods should be checked. See the
772 individual methods' documentation for details.
774 An exception carries the following pieces of information:
780 A numeric code that specifies the type of error. This can be checked
781 for equality with known values, so that intelligent applications can
782 take appropriate action.
786 A human-readable message corresponding with the code. This can be
787 shown to users, but its value should not be tested, as it could vary
788 in different versions or under different locales.
790 =item additional information [optional]
792 A string containing information specific to the error-code. For
793 example, when the error-code is the BIB-1 diagnostic 109 ("Database
794 unavailable"), the additional information is the name of the database
795 that the application tried to use. For some error-codes, there is no
796 additional information at all; for some others, the additional
797 information is undefined and may just be an human-readable string.
799 =item diagnostic set [optional]
801 A short string specifying the diagnostic set from which the error-code
802 was drawn: for example, C<ZOOM> for a ZOOM-specific error such as
803 C<ZOOM::Error::MEMORY> ("out of memory"), and C<BIB-1> for a Z39.50
804 error-code drawn from the BIB-1 diagnostic set.
808 In theory, the error-code should be interpreted in the context of the
809 diagnostic set from which it is drawn; in practice, nearly all errors
810 are from either the ZOOM or BIB-1 diagnostic sets, and the codes in
811 those sets have been chosen so as not to overlap, so the diagnostic
812 set can usually be ignored.
814 See the description of the C<Exception> class in the ZOOM Abstract
816 http://zoom.z3950.org/api/zoom-current.html#3.7
822 die new ZOOM::Exception($errcode, $errmsg, $addinfo, $diagset);
824 Creates and returns a new Exception object with the specified
825 error-code, error-message, additional information and diagnostic set.
826 Applications will not in general need to use this, but may find it
827 useful to simulate ZOOM exceptions. As is usual with Perl, exceptions
828 are thrown using C<die()>.
830 =head4 code() / message() / addinfo() / diagset()
832 print "Error ", $@->code(), ": ", $@->message(), "\n";
833 print "(addinfo '", $@->addinfo(), "', set '", $@->diagset(), "')\n";
835 These methods, of no arguments, return the exception's error-code,
836 error-message, additional information and diagnostic set respectively.
842 Returns a human-readable rendition of an exception. The C<"">
843 operator is overloaded on the Exception class, so that an Exception
844 used in a string context is automatically rendered. Among other
845 consequences, this has the useful result that a ZOOM application that
846 died due to an uncaught exception will emit an informative message
851 $ss = $conn->scan('@attr 1=1003 a');
853 ($term, $occ) = $ss->term($n-1);
854 $rs = $conn->search_pqf('@attr 1=1003 "' . $term . "'");
855 assert($rs->size() == $occ);
857 A ScanSet represents a set of candidate search-terms returned from an
858 index scan. Its sole purpose is to provide access to those term, to
859 the corresponding display terms, and to the occurrence-counts of the
862 There is no C<new()> method nor any other explicit constructor. The
863 only way to create a new ScanSet is by using C<scan()> on a
866 See the description of the C<Scan Set> class in the ZOOM Abstract
868 http://zoom.z3950.org/api/zoom-current.html#3.6
874 print "Found ", $ss->size(), " terms\n";
876 Returns the number of terms in the scan set. In general, this will be
877 the scan-set size requested by the C<number> option in the Connection
878 on which the scan was performed [default 10], but it may be fewer if
879 the scan is close to the end of the index.
881 =head4 term() / display_term()
883 $ss = $conn->scan('@attr 1=1004 whatever');
884 ($term, $occurrences) = $ss->term(0);
885 ($displayTerm, $occurrences2) = $ss->display_term(0);
886 assert($occurrences == $occurrences2);
887 if (user_likes_the_look_of($displayTerm)) {
888 $rs = $conn->search_pqf('@attr 1=4 "' . $term . '"');
889 assert($rs->size() == $occurrences);
892 These methods return the scanned terms themselves. C<term()> returns
893 the term is a form suitable for submitting as part of a query, whereas
894 C<display_term()> returns it in a form suitable for displaying to a
895 user. Both versions also return the number of occurrences of the term
896 in the index, i.e. the number of hits that will be found if the term
897 is subsequently used in a query.
899 In most cases, the term and display term will be identical; however,
900 they may be different in cases where punctuation or case is
901 normalised, or where identifiers rather than the original document
906 print "scan status is ", $ss->option("scanStatus");
908 Allows options to be set into, and read from, a ScanSet, just like
909 the Connection class's C<option()> method. There is no
910 C<option_binary()> method for ScanSet objects.
912 ScanSet options are also described, though not particularly
914 http://indexdata.com/yaz/doc/zoom.scan.tkl
920 Destroys a ScanSet object, freeing its resources. It is an error to
921 reuse a ScanSet that has been C<destroy()>ed.
925 $p = $conn->package();
926 $p->option(action => "specialUpdate");
927 $p->option(recordIdOpaque => 145);
928 $p->option(record => content_of("/tmp/record.xml"));
932 This class represents an Extended Services Package: an instruction to
933 the server to do something not covered by the core parts of the Z39.50
934 standard (or the equivalent in SRW or SRU). Since the core protocols
935 are read-only, such requests are often used to make changes to the
936 database, such as in the record update example above.
938 Requesting an extended service is a four-step process: first, create a
939 package associated with the connection to the relevant database;
940 second, set options on the package to instruct the server on what to
941 do; third, send the package (which may result in an exception being
942 thrown if the server cannot execute the requested operations; and
943 finally, destroy the package.
945 Package options are listed at
946 http://indexdata.com/yaz/doc/zoom.ext.tkl
948 The particular options that have meaning are determined by the
949 top-level operation string specified as the argument to C<send()>.
950 For example, when the operation is C<update> (the most commonly used
951 extended service), the C<action> option may be set to any of
953 (add a new record, failing if that record already exists),
955 (delete a record, failing if it is not in the database).
957 (replace a record, failing if an old version is not already present)
960 (add a record, replacing any existing version that may be present).
962 For update, the C<record> option should be set to the full text of the
963 XML record to added, deleted or replaced. Depending on how the server
964 is configured, it may extract the record's unique ID from the text
965 (i.e. from a known element such as the C<001> field of a MARCXML
966 record), or it may require the unique ID to passed in explicitly using
967 the C<recordIdOpaque> option.
969 Extended services packages are B<not currently described> in the ZOOM
971 http://zoom.z3950.org/api/zoom-current.html
972 They will be added in a forthcoming version, and will function much
973 as those implemented in this module.
979 $p->option(recordIdOpaque => "46696f6e61");
981 Allows options to be set into, and read from, a Package, just like
982 the Connection class's C<option()> method. There is no
983 C<option_binary()> method for Package objects.
985 Package options are listed at
986 http://indexdata.com/yaz/doc/zoom.ext.tkl
992 Sends a package to the server associated with the Connection that
993 created it. Problems are reported by throwing an exception. The
994 single parameter indicates the operation that the server is being
995 requested to perform, and controls the interpretation of the package's
996 options. Valid operations include:
1002 Request a copy of a nominated object, e.g. place an ILL request.
1006 Create a new database, the name of which is specified by the
1007 C<databaseName> option.
1011 Drop an existing database, the name of which is specified by the
1012 C<databaseName> option.
1016 Commit changes made to the database within a transaction.
1020 Modify the contents of the database by adding, deleting or replacing
1021 records (as described above in the overview of the C<ZOOM::Package>
1026 I have no idea what this does.
1030 Although the module is capable of I<making> all these requests, not
1031 all servers are capable of I<executing> them. Refusal is indicated by
1032 throwing an exception. Problems may also be caused by lack of
1033 privileges; so C<send()> must be used with caution, and is perhaps
1034 best wrapped in a clause that checks for execptions, like so:
1036 eval { $p->send("create") };
1037 if ($@ && $@->isa("ZOOM::Exception")) {
1038 print "Oops! ", $@->message(), "\n";
1046 Destroys a Package object, freeing its resources. It is an error to
1047 reuse a Package that has been C<destroy()>ed.
1051 $q = new ZOOM::Query::CQL("creator=pike and subject=unix");
1052 $q->sortby("1=4 >i 1=21 >s");
1053 $rs = $conn->search($q);
1056 C<ZOOM::Query> is a virtual base class from which various concrete
1057 subclasses can be derived. Different subclasses implement different
1058 types of query. The sole purpose of a Query object is to be used in a
1059 C<search()> on a Connection; because PQF is such a common special
1060 case, the shortcut Connection method C<search_pqf()> is provided.
1062 The following Query subclasses are provided, each providing the
1063 same set of methods described below:
1067 =item ZOOM::Query::PQF
1069 Implements Prefix Query Format (PQF), also sometimes known as Prefix
1070 Query Notation (PQN). This esoteric but rigorous and expressive
1071 format is described in the YAZ Manual at
1072 http://indexdata.com/yaz/doc/tools.tkl#PQF
1074 =item ZOOM::Query::CQL
1076 Implements the Common Query Language (CQL) of SRU, the Search/Retrieve
1077 URL. CQL is a much friendlier notation than PQF, using a simple infix
1078 notation. The queries are passed ``as is'' to the server rather than
1079 being compiled into a Z39.50 Type-1 query, so only CQL-compliant
1080 servers can support such querier. CQL is described at
1081 http://www.loc.gov/standards/sru/cql/
1082 and in a slight out-of-date but nevertheless useful tutorial at
1083 http://zing.z3950.org/cql/intro.html
1085 =item ZOOM::Query::CQL2RPN
1087 Implements CQL by compiling it on the client-side into a Z39.50
1088 Type-1 (RPN) query, and sending that. This provides essentially the
1089 same functionality as C<ZOOM::Query::CQL>, but it will work against
1090 any standard Z39.50 server rather than only against the small subset
1091 that support CQL natively. The drawback is that, because the
1092 compilation is done on the client side, a configuration file is
1093 required to direct the mapping of CQL constructs such as index names,
1094 relations and modifiers into Type-1 query attributes. An example CQL
1095 configuration file is included in the ZOOM-Perl distribution, in the
1096 file C<samples/cql/pqf.properties>
1098 =item ZOOM::Query::CCL2RPN
1100 Implements CCL by compiling it on the client-side into a Z39.50 Type-1
1101 (RPN) query, and sending that. Because the compilation is done on the
1102 client side, a configuration file is required to direct the mapping of
1103 CCL constructs such as index names and boolean operators into Type-1
1104 query attributes. An example CCL configuration file is included in
1105 the ZOOM-Perl distribution, in the file C<samples/ccl/default.bib>
1107 CCL is syntactically very similar to CQL, but much looser. While CQL
1108 is an entirely precise language in which each possible query has
1109 rigorously defined semantics, and is thus suitable for transfer as
1110 part of a protocol, CCL is best deployed as a human-facing UI
1115 See the description of the C<Query> class in the ZOOM Abstract
1117 http://zoom.z3950.org/api/zoom-current.html#3.3
1123 $q = new ZOOM::Query::CQL('title=dinosaur');
1124 $q = new ZOOM::Query::PQF('@attr 1=4 dinosaur');
1126 Creates a new query object, compiling the query passed as its argument
1127 according to the rules of the particular query-type being
1128 instantiated. If compilation fails, an exception is thrown.
1129 Otherwise, the query may be passed to the C<Connection> method
1132 $conn->option(cqlfile => "samples/cql/pqf.properties");
1133 $q = new ZOOM::Query::CQL2RPN('title=dinosaur', $conn);
1135 Note that for the C<ZOOM::Query::CQL2RPN> subclass, the Connection
1136 must also be passed into the constructor. This is used for two
1137 purposes: first, its C<cqlfile> option is used to find the CQL
1138 configuration file that directs the translations into RPN; and second,
1139 if compilation fails, then diagnostic information is cached in the
1140 Connection and be retrieved using C<$conn-E<gt>errcode()> and related
1143 $conn->option(cclfile => "samples/ccl/default.bib");
1145 $conn->option(cclqual => "ti u=4 s=pw\nab u=62 s=pw");
1146 $q = new ZOOM::Query::CCL2RPN('ti=dinosaur', $conn);
1148 For the C<ZOOM::Query::CCL2RPN> subclass, too, the Connection must be
1149 passed into the constructor, for the same reasons as when client-side
1150 CQL compilation is used. The C<cclqual> option, if defined, gives a
1151 CCL qualification specification inline; otherwise, the contents of the
1152 file named by the C<cclfile> option are used.
1156 $q->sortby("1=4 >i 1=21 >s");
1158 Sets a sort specification into the query, so that when a C<search()>
1159 is run on the query, the result is automatically sorted. The sort
1160 specification language is the same as the C<yaz> sort-specification
1161 type of the C<ResultSet> method C<sort()>, described above.
1167 Destroys a Query object, freeing its resources. It is an error to
1168 reuse a Query that has been C<destroy()>ed.
1170 =head2 ZOOM::Options
1172 $o1 = new ZOOM::Options();
1173 $o1->option(user => "alf");
1174 $o2 = new ZOOM::Options();
1175 $o2->option(password => "fruit");
1176 $opts = new ZOOM::Options($o1, $o2);
1177 $conn = create ZOOM::Connection($opts);
1178 $conn->connect($host); # Uses the specified username and password
1180 Several classes of ZOOM objects carry their own sets of options, which
1181 can be manipulated using their C<option()> method. Sometimes,
1182 however, it's useful to deal with the option sets directly, and the
1183 C<ZOOM::Options> class exists to enable this approach.
1185 Option sets are B<not currently described> in the ZOOM
1187 http://zoom.z3950.org/api/zoom-current.html
1188 They are an extension to that specification.
1194 $o1 = new ZOOM::Options();
1195 $o1and2 = new ZOOM::Options($o1);
1196 $o3 = new ZOOM::Options();
1197 $o1and3and4 = new ZOOM::Options($o1, $o3);
1199 Creates and returns a new option set. One or two (but no more)
1200 existing option sets may be passed as arguments, in which case they
1201 become ``parents'' of the new set, which thereby ``inherits'' their
1202 options, the values of the first parent overriding those of the second
1203 when both have a value for the same key. An option set that inherits
1204 from a parent that has its own parents also inherits the grandparent's
1207 =head4 option() / option_binary()
1209 $o->option(preferredRecordSyntax => "usmarc");
1210 $o->option_binary(iconBlob => "foo\0bar");
1211 die if length($o->option_binary("iconBlob") != 7);
1213 These methods are used to get and set options within a set, and behave
1214 the same way as the same-named C<Connection> methods - see above. As
1215 with the C<Connection> methods, values passed to and retrieved using
1216 C<option()> are interpreted as NUL-terminated, while those passed to
1217 and retrieved from C<option_binary()> are binary-clean.
1221 $o->option(x => "T");
1222 $o->option(y => "F");
1223 assert($o->bool("x", 1));
1224 assert(!$o->bool("y", 1));
1225 assert($o->bool("z", 1));
1227 The first argument is a key, and the second is a default value.
1228 Returns the value associated with the specified key as a boolean, or
1229 the default value if the key has not been set. The values C<T> (upper
1230 case) and C<1> are considered true; all other values (including C<t>
1231 (lower case) and non-zero integers other than one) are considered
1234 This method is provided in ZOOM-C because in a statically typed
1235 language it's convenient to have the result returned as an
1236 easy-to-test type. In a dynamically typed language such as Perl, this
1237 problem doesn't arise, so C<bool()> is nearly useless; but it is made
1238 available in case applications need to duplicate the idiosyncratic
1239 interpretation of truth and falsehood and ZOOM-C uses.
1243 $o->option(x => "012");
1244 assert($o->int("x", 20) == 12);
1245 assert($o->int("y", 20) == 20);
1247 Returns the value associated with the specified key as an integer, or
1248 the default value if the key has not been set. See the description of
1249 C<bool()> for why you almost certainly don't want to use this.
1253 $o->set_int(x => "29");
1255 Sets the value of the specified option as an integer. Of course, Perl
1256 happily converts strings to integers on its own, so you can just use
1257 C<option()> for this, but C<set_int()> is guaranteed to use the same
1258 string-to-integer conversion as ZOOM-C does, which might occasionally
1259 be useful. Though I can't imagine how.
1261 =head4 set_callback()
1265 return "$udata-$key-$udata";
1267 $o->set_callback(\&cb, "xyz");
1268 assert($o->option("foo") eq "xyz-foo-xyz");
1270 This method allows a callback function to be installed in an option
1271 set, so that the values of options can be calculated algorithmically
1272 rather than, as usual, looked up in a table. Along with the callback
1273 function itself, an additional datum is provided: when an option is
1274 subsequently looked up, this datum is passed to the callback function
1275 along with the key; and its return value is returned to the caller as
1276 the value of the option.
1279 Although it ought to be possible to specify callback function using
1280 the C<\&name> syntax above, or a literal C<sub { code }> code
1281 reference, the complexities of the Perl-internal memory management
1282 system mean that the function must currently be specified as a string
1283 containing the fully-qualified name, e.g. C<"main::cb">.>
1286 The current implementation of the this method leaks memory, not only
1287 when the callback is installed, but on every occasion that it is
1288 consulted to look up an option value.
1294 Destroys an Options object, freeing its resources. It is an error to
1295 reuse an Options object that has been C<destroy()>ed.
1299 The ZOOM module provides two enumerations that list possible return
1300 values from particular functions. They are described in the following
1305 if ($@->code() == ZOOM::Error::QUERY_PQF) {
1306 return "your query was not accepted";
1309 This class provides a set of manifest constants representing some of
1310 the possible error codes that can be raised by the ZOOM module. The
1311 methods that return error-codes are
1312 C<ZOOM::Exception::code()>,
1313 C<ZOOM::Connection::error_x()>
1315 C<ZOOM::Connection::errcode()>.
1317 The C<ZOOM::Error> class provides the constants
1327 C<UNSUPPORTED_PROTOCOL>,
1328 C<UNSUPPORTED_QUERY>,
1343 each of which specifies a client-side error. These codes constitute
1344 the C<ZOOM> diagnostic set.
1346 Since errors may also be diagnosed by the server, and returned to the
1347 client, error codes may also take values from the BIB-1 diagnostic set
1348 of Z39.50, listed at the Z39.50 Maintenance Agency's web-site at
1349 http://www.loc.gov/z3950/agency/defns/bib1diag.html
1351 All error-codes, whether client-side from the C<ZOOM::Error>
1352 enumeration or server-side from the BIB-1 diagnostic set, can be
1353 translated into human-readable messages by passing them to the
1354 C<ZOOM::diag_str()> utility function.
1358 if ($conn->last_event() == ZOOM::Event::CONNECT) {
1359 print "Connected!\n";
1362 In applications that need it - mostly complex multiplexing
1363 applications - The C<ZOOM::Connection::last_event()> method is used to
1364 return an indication of the last event that occurred on a particular
1365 connection. It always returns a value drawn from this enumeration,
1366 that is, one of C<NONE>, C<CONNECT>, C<SEND_DATA>, C<RECV_DATA>,
1367 C<TIMEOUT>, C<UNKNOWN>, C<SEND_APDU>, C<RECV_APDU>, C<RECV_RECORD>,
1368 C<RECV_SEARCH> or C<ZEND>.
1370 See the section below on asynchronous applications.
1374 ZOOM::Log::init_level(ZOOM::Log::mask_str("zoom,myapp,-warn"));
1375 ZOOM::Log::log("myapp", "starting up with pid ", $$);
1377 Logging facilities are provided by a set of functions in the
1378 C<ZOOM::Log> module. Note that C<ZOOM::Log> is not a class, and it
1379 is not possible to create C<ZOOM::Log> objects: the API is imperative,
1380 reflecting that of the underlying YAZ logging facilities. Although
1381 there are nine logging functions altogether, you can ignore nearly
1382 all of them: most applications that use logging will begin by calling
1383 C<mask_str()> and C<init_level()> once each, as above, and will then
1384 repeatedly call C<log()>.
1388 $level = ZOOM::Log::mask_str("zoom,myapp,-warn");
1390 Returns an integer corresponding to the log-level specified by the
1391 parameter. This is a string of zero or more comma-separated
1392 module-names, each indicating an individual module to be either added
1393 to the default log-level or removed from it (for those components
1394 prefixed by a minus-sign). The names may be those of either standard
1395 YAZ-logging modules such as C<fatal>, C<debug> and C<warn>, or custom
1396 modules such as C<myapp> in the example above. The module C<zoom>
1397 requests logging from the ZOOM module itself, which may be helpful for
1400 Note that calling this function does not in any way change the logging
1401 state: it merely returns a value. To change the state, this value
1402 must be passed to C<init_level()>.
1404 =head2 module_level()
1406 $level = ZOOM::Log::module_level("zoom");
1407 ZOOM::Log::log($level, "all systems clear: thrusters invogriated");
1409 Returns the integer corresponding to the single log-level specified as
1410 the parameter, or zero if that level has not been registered by a
1411 prior call to C<mask_str()>. Since C<log()> accepts either a numeric
1412 log-level or a string, there is no reason to call this function; but,
1413 what the heck, maybe you enjoy that kind of thing. Who are we to
1418 ZOOM::Log::init_level($level);
1420 Initialises the log-level to the specified integer, which is a bitmask
1421 of values, typically as returned from C<mask_str()>. All subsequent
1422 calls to C<log()> made with a log-level that matches one of the bits
1423 in this mask will result in a log-message being emitted. All logging
1424 can be turned off by calling C<init_level(0)>.
1426 =head2 init_prefix()
1428 ZOOM::Log::init_prefix($0);
1430 Initialises a prefix string to be included in all log-messages.
1434 ZOOM::Log::init_file("/tmp/myapp.log");
1436 Initialises the output file to be used for logging: subsequent
1437 log-messages are written to the nominated file. If this function is
1438 not called, log-messages are written to the standard error stream.
1442 ZOOM::Log::init($level, $0, "/tmp/myapp.log");
1444 Initialises the log-level, the logging prefix and the logging output
1445 file in a single operation.
1447 =head2 time_format()
1449 ZOOM::Log::time_format("%Y-%m-%d %H:%M:%S");
1451 Sets the format in which log-messages' timestamps are emitted, by
1452 means of a format-string like that used in the C function
1453 C<strftime()>. The example above emits year, month, day, hours,
1454 minutes and seconds in big-endian order, such that timestamps can be
1455 sorted lexicographically.
1457 =head2 init_max_size()
1459 (This doesn't seem to work, so I won't bother describing it.)
1463 ZOOM::Log::log(8192, "reducing to warp-factor $wf");
1464 ZOOM::Log::log("myapp", "starting up with pid ", $$);
1466 Provided that the first argument, log-level, is among the modules
1467 previously established by C<init_level()>, this function emits a
1468 log-message made up of a timestamp, the prefix supplied to
1469 C<init_prefix()>, if any, and the concatenation of all arguments after
1470 the first. The message is written to the standard output stream, or
1471 to the file previous specified by C<init_file()> if this has been
1474 The log-level argument may be either a numeric value, as returned from
1475 C<module_level()>, or a string containing the module name.
1477 =head1 ASYNCHRONOUS APPLICATIONS
1479 Although asynchronous applications are conceptually complex, the ZOOM
1480 support for them is provided through a very simple interface,
1481 consisting of one option (C<async>), one function (C<ZOOM::event()>),
1482 one Connection method (C<last_event()> and an enumeration
1485 The approach is as follows:
1489 =item Initialisation
1491 Create several connections to the various servers, each of them having
1492 the option C<async> set, and with whatever additional options are
1493 required - e.g. the piggyback retrieval record-count can be set so
1494 that records will be returned in search responses.
1498 Send searches to the connections, request records, etc.
1500 =item Event harvesting
1502 Repeatedly call C<ZOOM::event()> to discover what responses are being
1503 received from the servers. Each time this function returns, it
1504 indicates which of the connections has fired; this connection can then
1505 be interrogated with the C<last_event()> method to discover what event
1506 has occurred, and the return value - an element of the C<ZOOM::Event>
1507 enumeration - can be tested to determine what to do next. For
1508 example, the C<ZEND> event indicates that no further operations are
1509 outstanding on the connection, so any fetched records can now be
1510 immediately obtained.
1514 Here is a very short program (omitting all error-checking!) which
1515 demonstrates this process. It parallel-searches three servers (or more
1516 of you add them the list), displaying the first record in the
1517 result-set of each server as soon as it becomes available.
1520 @servers = ('z3950.loc.gov:7090/Voyager',
1521 'z3950.indexdata.com:210/gils',
1522 'agricola.nal.usda.gov:7190/Voyager');
1523 for ($i = 0; $i < @servers; $i++) {
1524 $z[$i] = new ZOOM::Connection($servers[$i], 0,
1525 async => 1, # asynchronous mode
1526 count => 1, # piggyback retrieval count
1527 preferredRecordSyntax => "usmarc");
1528 $r[$i] = $z[$i]->search_pqf("mineral");
1530 while (($i = ZOOM::event(\@z)) != 0) {
1531 $ev = $z[$i-1]->last_event();
1532 print("connection ", $i-1, ": ", ZOOM::event_str($ev), "\n");
1533 if ($ev == ZOOM::Event::ZEND) {
1534 $size = $r[$i-1]->size();
1535 print "connection ", $i-1, ": $size hits\n";
1536 print $r[$i-1]->record(0)->render()
1543 The ZOOM abstract API,
1544 http://zoom.z3950.org/api/zoom-current.html
1546 The C<Net::Z3950::ZOOM> module, included in the same distribution as this one.
1548 The C<Net::Z3950> module, which this one supersedes.
1549 http://perl.z3950.org/
1551 The documentation for the ZOOM-C module of the YAZ Toolkit, which this
1552 module is built on. Specifically, its lists of options are useful.
1553 http://indexdata.com/yaz/doc/zoom.tkl
1555 The BIB-1 diagnostic set of Z39.50,
1556 http://www.loc.gov/z3950/agency/defns/bib1diag.html
1560 Mike Taylor, E<lt>mike@indexdata.comE<gt>
1562 =head1 COPYRIGHT AND LICENCE
1564 Copyright (C) 2005 by Index Data.
1566 This library is free software; you can redistribute it and/or modify
1567 it under the same terms as Perl itself, either Perl version 5.8.4 or,
1568 at your option, any later version of Perl 5 you may have available.