1 <!-- $Id: zoom.xml,v 1.36 2003-11-25 09:55:20 mike Exp $ -->
2 <chapter id="zoom"><title>ZOOM</title>
4 &zoom; is an acronym for 'Z39.50 Object-Orientation Model' and is
5 an initiative started by Mike Taylor (Mike is from the UK, which
6 explains the peculiar name of the model). The goal of &zoom; is to
7 provide a common Z39.50 client API not bound to a particular
8 programming language or toolkit.
13 A recent addition to &yaz; is SRW support. You can now make
14 SRW ZOOM connections by specifying scheme <literal>http://</literal>
15 for the hostname for a connection.
20 The lack of a simple Z39.50 client API for &yaz; has become more
21 and more apparent over time. So when the first &zoom; specification
23 an implementation for &yaz; was quickly developed. For the first time, it is
24 now as easy (or easier!) to develop clients than servers with &yaz;. This
25 chapter describes the &zoom; C binding. Before going further, please
26 reconsider whether C is the right programming language for the job.
27 There are other language bindings available for &yaz;, and still
29 are in active development. See the
30 <ulink url="http://zoom.z3950.org/">ZOOM web-site</ulink> for
35 In order to fully understand this chapter you should read and
36 try the example programs <literal>zoomtst1.c</literal>,
37 <literal>zoomtst2.c</literal>, .. in the <literal>zoom</literal>
42 The C language misses features found in object oriented languages
43 such as C++, Java, etc. For example, you'll have to manually,
44 destroy all objects you create, even though you may think of them as
45 temporary. Most objects has a <literal>_create</literal> - and a
46 <literal>_destroy</literal> variant.
47 All objects are in fact pointers to internal stuff, but you don't see
48 that because of typedefs. All destroy methods should gracefully ignore a
49 <literal>NULL</literal> pointer.
52 In each of the sections below you'll find a sub section called
53 protocol behavior, that describes how the API maps to the Z39.50
56 <sect1 id="zoom.connections"><title>Connections</title>
58 <para>The Connection object is a session with a target.
61 #include <yaz/zoom.h>
63 ZOOM_connection ZOOM_connection_new (const char *host, int portnum);
65 ZOOM_connection ZOOM_connection_create (ZOOM_options options);
67 void ZOOM_connection_connect(ZOOM_connection c, const char *host,
69 void ZOOM_connection_destroy (ZOOM_connection c);
72 Connection objects are created with either function
73 <function>ZOOM_connection_new</function> or
74 <function>ZOOM_connection_create</function>.
75 The former creates and automatically attempts to establish a network
76 connection with the target. The latter doesn't establish
77 a connection immediately, thus allowing you to specify options
78 before establishing network connection using the function
79 <function>ZOOM_connection_connect</function>.
80 If the port number, <literal>portnum</literal>, is zero, the
81 <literal>host</literal> is consulted for a port specification.
82 If no port is given, 210 is used. A colon denotes the beginning of
83 a port number in the host string. If the host string includes a
84 slash, the following part specifies a database for the connection.
87 You can prefix the host with a scheme followed by colon. The
88 default scheme is <literal>tcp</literal> (Z39.50 protocol).
89 The scheme <literal>http</literal> selects SRW over HTTP.
92 Connection objects should be destroyed using the function
93 <function>ZOOM_connection_destroy</function>.
96 void ZOOM_connection_option_set (ZOOM_connection c,
100 const char *ZOOM_connection_option_get (ZOOM_connection c,
104 The <function>ZOOM_connection_option_set</function> allows you to
105 set an option given by <parameter>key</parameter> to the value
106 <parameter>value</parameter> for the connection.
107 Function <function>ZOOM_connection_option_get</function> returns
108 the value for an option given by <parameter>key</parameter>.
110 <table frame="top"><title>ZOOM Connection Options</title>
112 <colspec colwidth="4*" colname="name"></colspec>
113 <colspec colwidth="7*" colname="description"></colspec>
114 <colspec colwidth="3*" colname="default"></colspec>
117 <entry>Option</entry>
118 <entry>Description</entry>
119 <entry>Default</entry>
124 implementationName</entry><entry>Name of Your client
125 </entry><entry>none</entry></row>
127 user</entry><entry>Authentication user name
128 </entry><entry>none</entry></row>
130 group</entry><entry>Authentication group name
131 </entry><entry>none</entry></row>
133 pass</entry><entry>Authentication password
134 </entry><entry>none</entry></row>
136 host</entry><entry>Target host. This setting is "read-only".
137 It's automatically set internally when connecting to a target.
138 </entry><entry>none</entry></row>
140 proxy</entry><entry>Proxy host
141 </entry><entry>none</entry></row>
143 async</entry><entry>If true (1) the connection operates in
144 asynchronous operation which means that all calls are non-blocking
146 <link linkend="zoom.events"><function>ZOOM_event</function></link>.
147 </entry><entry>0</entry></row>
149 maximumRecordSize</entry><entry> Maximum size of single record.
150 </entry><entry>1 MB</entry></row>
152 preferredMessageSize</entry><entry> Maximum size of multiple records.
153 </entry><entry>1 MB</entry></row>
155 lang</entry><entry> Language for negotiation.
156 </entry><entry>none</entry></row>
158 charset</entry><entry> Character set for negotiation.
159 </entry><entry>none</entry></row>
161 serverImplementationId</entry><entry>
162 Implementation ID of server. (The old targetImplementationId
163 option is also supported for the benefit of old applications.)
164 </entry><entry>none</entry></row>
166 targetImplementationName</entry><entry>
167 Implementation Name of server. (The old
168 targetImplementationName option is also supported for the
169 benefit of old applications.)
170 </entry><entry>none</entry></row>
172 serverImplementationVersion</entry><entry>
173 Implementation Version of server. (the old
174 targetImplementationVersion option is also supported for the
175 benefit of old applications.)
176 </entry><entry>none</entry></row>
178 databaseName</entry><entry>One or more database names
179 separated by character plus (<literal>+</literal>), which to
180 be used by subsequent search requests on this Connection.
181 </entry><entry>Default</entry></row>
183 piggyback</entry><entry>True (1) if piggyback should be
184 used in searches; false (0) if not.
185 </entry><entry>1</entry></row>
187 smallSetUpperBound</entry><entry>If hits is less than or equal to this
188 value, then target will return all records using small element set name
189 </entry><entry>0</entry></row>
191 largeSetLowerBound</entry><entry>If hits is greater than this
192 value, the target will return no records.
193 </entry><entry>1</entry></row>
195 mediumSetPresentNumber</entry><entry>This value represents
196 the number of records to be returned as part of a search when when
197 hits is less than or equal to large set lower bound and if hits
198 is greater than small set upper bound.
199 </entry><entry>0</entry></row>
201 smallSetElementSetName</entry><entry>
202 The element set name to be used for small result sets.
203 </entry><entry>none</entry></row>
205 mediumSetElementSetName</entry><entry>
206 The element set name to be for medium-sized result sets.
207 </entry><entry>none</entry></row>
212 If either option <literal>lang</literal> or <literal>charset</literal>
214 <ulink url="http://lcweb.loc.gov/z3950/agency/defns/charneg-3.html">
215 Character Set and Language Negotiation</ulink> is in effect.
218 int ZOOM_connection_error (ZOOM_connection c, const char **cp,
219 const char **addinfo);
220 int ZOOM_connection_error_x (ZOOM_connection c, const char **cp,
221 const char **addinfo, const char **dset);
224 Function <function>ZOOM_connection_error</function> checks for
225 errors for the last operation(s) performed. The function returns
226 zero if no errors occurred; non-zero otherwise indicating the error.
227 Pointers <parameter>cp</parameter> and <parameter>addinfo</parameter>
228 holds messages for the error and additional-info if passed as
229 non-<literal>NULL</literal>. Function
230 <function>ZOOM_connection_error_x</function> is an extended version
231 of <function>ZOOM_connection_error</function> that is capable of
232 returning name of diagnostic set in <parameter>dset</parameter>.
234 <sect2><title>Z39.50 Protocol behavior</title>
236 The calls <function>ZOOM_connection_new</function> and
237 <function>ZOOM_connection_connect</function> establishes a TCP/IP
238 connection and sends an Initialize Request to the target if
239 possible. In addition, the calls waits for an Initialize Response
240 from the target and the result is inspected (OK or rejected).
243 If <literal>proxy</literal> is set then the client will establish
244 a TCP/IP connection with the peer as specified by the
245 <literal>proxy</literal> host and the hostname as part of the
246 connect calls will be set as part of the Initialize Request.
247 The proxy server will then "forward" the PDU's transparently
248 to the target behind the proxy.
251 For the authentication parameters, if option <literal>user</literal>
252 is set and both options <literal>group</literal> and
253 <literal>pass</literal> are unset, then Open style
254 authentication is used (Version 2/3) in which case the username
255 is usually followed by a slash, then by a password.
256 If either <literal>group</literal>
257 or <literal>pass</literal> is set then idPass authentication
258 (Version 3 only) is used. If none of the options are set, no
259 authentication parameters are set as part of the Initialize Request
263 When option <literal>async</literal> is 1, it really means that
264 all network operations are postponed (and queued) until the
265 function <literal>ZOOM_event</literal> is invoked. When doing so
266 it doesn't make sense to check for errors after
267 <literal>ZOOM_connection_new</literal> is called since that
268 operation "connecting - and init" is still incomplete and the
269 API cannot tell the outcome (yet).
272 <sect2><title>SRW Protocol behavior</title>
274 The SRW protocol doesn't feature an Inititialize Request, so
275 the connection phase merely establishes a TCP/IP connection
276 with the SOAP service.
278 <para>Most of the ZOOM connection options do not
279 affect SRW and they are ignored. However, future versions
280 of &yaz; might honor <literal>implementationName</literal> and
281 put that as part of User-Agent header for HTTP requests.
284 The <literal>charset</literal> is used in the Content-Type header
289 <sect1 id="zoom.query"><title>Queries</title>
291 Query objects represents queries.
294 ZOOM_query ZOOM_query_create(void);
296 void ZOOM_query_destroy(ZOOM_query q);
298 int ZOOM_query_prefix(ZOOM_query q, const char *str);
300 int ZOOM_query_cql(ZOOM_query s, const char *str);
302 int ZOOM_query_sortby(ZOOM_query q, const char *criteria);
305 Create query objects using <function>ZOOM_query_create</function>
306 and destroy them by calling <function>ZOOM_query_destroy</function>.
307 RPN-queries can be specified in <link linkend="PQF">PQF</link>
308 notation by using the
309 function <function>ZOOM_query_prefix</function>.
310 The <function>ZOOM_query_cql</function> specifies a CQL
311 query to be sent to the server/target.
312 More query types will be added in future versions of &yaz;, such as
313 <link linkend="CCL">CCL</link> to RPN-mapping, native CCL query,
314 etc. In addition to a search, a sort criteria may be set. Function
315 <function>ZOOM_query_sortby</function> specifies a
316 sort criteria using the same string notation for sort as offered by
317 the <link linkend="sortspec">YAZ client</link>.
319 <sect2><title>Protocol behavior</title>
321 The query object is just an interface for the member Query
322 in the SearchRequest. The sortby-function is an interface to the
323 sortSequence member of the SortRequest.
327 <sect1 id="zoom.resultsets"><title>Result sets</title>
329 The result set object is a container for records returned from
333 ZOOM_resultset ZOOM_connection_search(ZOOM_connection,
336 ZOOM_resultset ZOOM_connection_search_pqf(ZOOM_connection c,
339 void ZOOM_resultset_destroy(ZOOM_resultset r);
342 Function <function>ZOOM_connection_search</function> creates
343 a result set given a connection and query.
344 Destroy a result set by calling
345 <function>ZOOM_resultset_destroy</function>.
346 Simple clients may using PQF only may use function
347 <function>ZOOM_connection_search_pqf</function> in which case
348 creating query objects is not necessary.
351 void ZOOM_resultset_option_set (ZOOM_resultset r,
355 const char *ZOOM_resultset_option_get (ZOOM_resultset r,
358 size_t ZOOM_resultset_size (ZOOM_resultset r);
361 Functions <function>ZOOM_resultset_options_set</function> and
362 <function>ZOOM_resultset_get</function> sets and gets an option
363 for a result set similar to <function>ZOOM_connection_option_get</function>
364 and <function>ZOOM_connection_option_set</function>.
367 The number of hits also called result-count is returned by
368 function <function>ZOOM_resultset_size</function>.
370 <table frame="top"><title>ZOOM Result set Options</title>
372 <colspec colwidth="4*" colname="name"></colspec>
373 <colspec colwidth="7*" colname="description"></colspec>
374 <colspec colwidth="2*" colname="default"></colspec>
377 <entry>Option</entry>
378 <entry>Description</entry>
379 <entry>Default</entry>
384 start</entry><entry>Offset of first record to be
385 retrieved from target. First record has offset 0 unlike the
386 protocol specifications where first record has position 1.
387 </entry><entry>0</entry></row>
389 count</entry><entry>Number of records to be retrieved.
390 </entry><entry>0</entry></row>
392 presentChunk</entry><entry>The number of records to be
393 requested from the server in each chunk (present requst). The
394 value 0 means to request all the records in a single chunk.
395 (The old <literal>step</literal>
396 option is also supported for the benefit of old applications.)
397 </entry><entry>0</entry></row>
399 elementSetName</entry><entry>Element-Set name of records.
400 Most targets should honor element set name <literal>B</literal>
401 and <literal>F</literal> for brief and full respectively.
402 </entry><entry>none</entry></row>
404 preferredRecordSyntax</entry><entry>Preferred Syntax, such as
405 <literal>USMARC</literal>, <literal>SUTRS</literal>, etc.
406 </entry><entry>none</entry></row>
408 schema</entry><entry>Schema for retrieval, such as
409 <literal>Gils-schema</literal>, <literal>Geo-schema</literal>, etc.
410 </entry><entry>none</entry></row>
412 setname</entry><entry>Name of Result Set (Result Set ID).
413 If this option isn't set, the ZOOM module will automatically
414 allocate a result set name.
415 </entry><entry>default</entry></row>
420 <title>Z39.50 Protocol behavior</title>
422 The creation of a result set involves at least a SearchRequest
423 - SearchResponse protocol handshake. Following that, if a sort
424 criteria was specified as part of the query, a SortRequest -
425 SortResponse handshake takes place. Note that it is necessary to
426 perform sorting before any retrieval takes place, so no records will
427 be returned from the target as part of the SearchResponse because these
428 would be unsorted. Hence, piggyback is disabled when sort criteria
429 are set. Following Search - and a possible sort - Retrieval takes
430 place - as one or more Present Requests/Response pairs being
434 The API allows for two different modes for retrieval. A high level
435 mode which is somewhat more powerful and a low level one.
436 The low level is enabled when searching on a Connection object
437 for which the settings
438 <literal>smallSetUpperBound</literal>,
439 <literal>mediumSetPresentNumber</literal> and
440 <literal>largeSetLowerBound</literal> are set. The low level mode
441 thus allows you to precisely set how records are returned as part
442 of a search response as offered by the Z39.50 protocol.
443 Since the client may be retrieving records as part of the
444 search response, this mode doesn't work well if sorting is used.
447 The high-level mode allows you to fetch a range of records from
448 the result set with a given start offset. When you use this mode
449 the client will automatically use piggyback if that is possible
450 with the target and perform one or more present requests as needed.
451 Even if the target returns fewer records as part of a present response
452 because of a record size limit, etc. the client will repeat sending
453 present requests. As an example, if option <literal>start</literal>
454 is 0 (default) and <literal>count</literal> is 4, and
455 <literal>piggyback</literal> is 1 (default) and no sorting criteria
456 is specified, then the client will attempt to retrieve the 4
457 records as part the search response (using piggyback). On the other
458 hand, if either <literal>start</literal> is positive or if
459 a sorting criteria is set, or if <literal>piggyback</literal>
460 is 0, then the client will not perform piggyback but send Present
464 If either of the options <literal>mediumSetElementSetName</literal> and
465 <literal>smallSetElementSetName</literal> are unset, the value
466 of option <literal>elementSetName</literal> is used for piggyback
467 searches. This means that for the high-level mode you only have
468 to specify one elementSetName option rather than three.
472 <title>SRW Protocol behavior</title>
474 Current version of &yaz; does not take advantage of a result set id
475 returned by the SRW server. Future versions might do, however.
476 Since, the ZOOM driver does not save result set IDs any
477 present (retrieval) is transformed to a SRW SearchRetrieveRequest
478 with same query but, possibly, different offsets.
481 Option <literal>schema</literal> specifies SRW schema
482 for retrieval. However, options <literal>elementSetName</literal> and
483 <literal>preferredRecordSyntax</literal> are ignored.
486 Options <literal>start</literal> and <literal>count</literal>
487 are supported by SRW.
488 The remaining options
489 <literal>piggyback</literal>,
490 <literal>smallSetUpperBound</literal>,
491 <literal>largeSetLowerBound</literal>,
492 <literal>mediumSetPresentNumber</literal>,
493 <literal>mediumSetElementSetName</literal>,
494 <literal>smallSetElementSetName</literal> are
498 SRW supports CQL queries, <emphasis>not</emphasis> PQF.
499 If PQF is used, however, the PQF query is transferred anyway
500 using non-standard element <literal>pQuery</literal> in
501 SRW SearchRetrieveRequest.
504 Unfortunately, SRW does not define a database setting. Hence,
505 <literal>databaseName</literal> is unsupported and ignored.
506 However, the path part in host parameter for functions
507 <function>ZOOM_connecton_new</function> and
508 <function>ZOOM_connection_connect</function> acts as a
509 database (at least for the &yaz; SRW server).
513 <sect1 id="zoom.records"><title>Records</title>
515 A record object is a retrieval record on the client side -
516 created from result sets.
519 void ZOOM_resultset_records (ZOOM_resultset r,
521 size_t start, size_t count);
522 ZOOM_record ZOOM_resultset_record (ZOOM_resultset s, size_t pos);
524 const char *ZOOM_record_get (ZOOM_record rec, const char *type,
527 ZOOM_record ZOOM_record_clone (ZOOM_record rec);
529 void ZOOM_record_destroy (ZOOM_record rec);
532 References to temporary records are returned by functions
533 <function>ZOOM_resultset_records</function> or
534 <function>ZOOM_resultset_record</function>.
537 If a persistent reference to a record is desired
538 <function>ZOOM_record_clone</function> should be used.
539 It returns a record reference that should be destroyed
540 by a call to <function>ZOOM_record_destroy</function>.
543 A single record is returned by function
544 <function>ZOOM_resultset_record</function> that takes a
545 position as argument. First record has position zero.
546 If no record could be obtained <literal>NULL</literal> is returned.
549 Function <function>ZOOM_resultset_records</function> retrieves
550 a number of records from a result set. Parameter <literal>start</literal>
551 and <literal>count</literal> specifies the range of records to
552 be returned. Upon completion array
553 <literal>recs[0], ..recs[count-1]</literal>
554 holds record objects for the records. The array of records
555 <literal>recs</literal> should be allocated prior the call
556 <function>ZOOM_resultset_records</function>. Note that for those
557 records that couldn't be retrieved from the target
558 <literal>recs[ ..]</literal> is set to <literal>NULL</literal>.
560 <para id="zoom.record.get">
561 In order to extract information about a single record,
562 <function>ZOOM_record_get</function> is provided. The
563 function returns a pointer to certain record information. The
564 nature (type) of the pointer depends on the parameter,
565 <parameter>type</parameter>.
568 The <parameter>type</parameter> is a string of the format:
571 <replaceable>form</replaceable>[; charset=<replaceable>from</replaceable>[,<replaceable>to</replaceable>]]
574 where <replaceable>form</replaceable> specifies the format of the
575 returned record, <replaceable>from</replaceable>
576 specifies the character set of the record in its original form
577 (as returned by the server), <replaceable>to</replaceable> specifies
578 the output (returned)
579 character set encoding.
580 If charset is not given, then no character set conversion takes place.
581 If <replaceable>to</replaceable> is omitted UTF-8 is assumed.
584 In addition, for certain types, the length
585 <literal>len</literal> passed will be set to the size in bytes of
586 the returned information.
589 The following are the supported values for <replaceable>form</replaceable>.
591 <varlistentry><term><literal>database</literal></term>
592 <listitem><para>Database of record is returned
593 as a C null-terminated string. Return type
594 <literal>const char *</literal>.
597 <varlistentry><term><literal>syntax</literal></term>
598 <listitem><para>The transfer syntax of the record is returned
599 as a C null-terminated string containing the symbolic name of
600 the record syntax, e.g. <literal>Usmarc</literal>. Return type
602 <literal>const char *</literal>.
605 <varlistentry><term><literal>render</literal></term>
606 <listitem><para>The record is returned in a display friendly
607 format. Upon completion buffer is returned
608 (type <literal>const char *</literal>) and length is stored in
609 <literal>*len</literal>.
612 <varlistentry><term><literal>raw</literal></term>
613 <listitem><para>The record is returned in the internal
614 YAZ specific format. For GRS-1, Explain, and others, the
615 raw data is returned as type
616 <literal>Z_External *</literal> which is just the type for
617 the member <literal>retrievalRecord</literal> in
618 type <literal>NamePlusRecord</literal>.
619 For SUTRS and octet aligned record (including all MARCs) the
620 octet buffer is returned and the length of the buffer.
623 <varlistentry><term><literal>xml</literal></term>
624 <listitem><para>The record is returned in XML if possible.
625 SRW/SRU and Z39.50 records with transfer syntax XML are
626 returned verbatim. MARC records are returned in
627 <ulink url="http://www.loc.gov/standards/marcxml/">
630 (converted from ISO2709 to MARCXML by YAZ).
631 GRS-1 and OPAC records are not supported for this form.
632 Upon completion, the XML buffer is returned
633 (type <literal>const char *</literal>) and length is stored in
634 <literal>*len</literal>.
637 <varlistentry><term><literal>opac</literal></term>
638 <listitem><para>OPAC for record is returned in XML.
645 <ulink url="http://www.loc.gov/marc/">
649 <ulink url="http://www.loc.gov/marc/specifications/speccharmarc8.html">
652 character set encoding.
653 An application that wishes to display in Latin-1 would use
655 render; charset=marc8,iso-8859-1
658 <sect2><title>Z39.50 Protocol behavior</title>
660 The functions <function>ZOOM_resultset_record</function> and
661 <function>ZOOM_resultset_records</function> inspects the client-side
662 record cache. Records not found in cache are fetched using
664 The functions may block (and perform network I/O) - even though option
665 <literal>async</literal> is 1, because they return records objects.
666 (and there's no way to return records objects without retrieving them!).
669 There is a trick, however, in the usage of function
670 <function>ZOOM_resultset_records</function> that allows for
671 delayed retrieval (and makes it non-blocking). By using
672 a null pointer for <parameter>recs</parameter> you're indicating
673 you're not interested in getting records objects
674 <emphasis>now</emphasis>.
677 <sect2><title>SRW Protocol behavior</title>
679 The ZOOM driver for SRW treats records returned by a SRW server
680 as if they where Z39.50 records with transfer syntax XML and
681 no element set name or database name.
685 <sect1 id="zoom.scan"><title>Scan</title>
687 This section describes an interface for Scan. Scan is not an
688 official part of the ZOOM model yet. The result of a scan operation
689 is the <literal>ZOOM_scanset</literal> which is a set of terms
690 returned by a target.
694 The Scan interface is Z39.50 only. SRW version 1.0 does not
699 ZOOM_scanset ZOOM_connection_scan (ZOOM_connection c,
700 const char *startterm);
702 size_t ZOOM_scanset_size(ZOOM_scanset scan);
704 const char * ZOOM_scanset_term(ZOOM_scanset scan, size_t pos,
705 int *occ, size_t *len);
707 const char * ZOOM_scanset_display_term(ZOOM_scanset scan, size_t pos,
708 int *occ, size_t *len);
710 void ZOOM_scanset_destroy (ZOOM_scanset scan);
712 const char *ZOOM_scanset_option_get (ZOOM_scanset scan,
715 void ZOOM_scanset_option_set (ZOOM_scanset scan, const char *key,
719 The scan set is created by function
720 <function>ZOOM_connection_scan</function> which performs a scan
721 operation on the connection using the specified startterm.
722 If the operation was successful, the size of the scan set can be
723 retrieved by a call to <function>ZOOM_scanset_size</function>.
724 Like result sets, the items are numbered 0,..size-1.
725 To obtain information about a particular scan term, call function
726 <function>ZOOM_scanset_term</function>. This function takes
727 a scan set offset <literal>pos</literal> and returns a pointer
728 to a <emphasis>raw term</emphasis> or <literal>NULL</literal> if
730 If present, the <literal>occ</literal> and <literal>len</literal>
731 are set to the number of occurrences and the length
732 of the actual term respectively.
733 <function>ZOOM_scanset_display_term</function> is similar to
734 <function>ZOOM_scanset_term</function> except that it returns
735 the <emphasis>display term</emphasis> rather than the raw term.
736 In a few cases, the term is different from display term. Always
737 use the display term for display and the raw term for subsequent
738 scan operations (to get more terms, next scan result, etc).
741 A scan set may be freed by a call to function
742 <function>ZOOM_scanset_destroy</function>.
743 Functions <function>ZOOM_scanset_option_get</function> and
744 <function>ZOOM_scanset_option_set</function> retrieves and sets
745 an option respectively.
748 <table frame="top"><title>ZOOM Scan Set Options</title>
750 <colspec colwidth="4*" colname="name"></colspec>
751 <colspec colwidth="7*" colname="description"></colspec>
752 <colspec colwidth="2*" colname="default"></colspec>
755 <entry>Option</entry>
756 <entry>Description</entry>
757 <entry>Default</entry>
762 number</entry><entry>Number of Scan Terms requested in next scan.
763 After scan it holds the actual number of terms returned.
764 </entry><entry>10</entry></row>
766 position</entry><entry>Preferred Position of term in response
767 in next scan; actual position after completion of scan.
768 </entry><entry>1</entry></row>
770 stepSize</entry><entry>Step Size
771 </entry><entry>0</entry></row>
773 scanStatus</entry><entry>An integer indicating the Scan Status
775 </entry><entry>0</entry></row>
781 <sect1 id="zoom.options"><title>Options</title>
783 Most &zoom; objects provide a way to specify options to change behavior.
784 From an implementation point of view a set of options is just like
785 an associative array / hash array, etc.
788 ZOOM_options ZOOM_options_create (void);
790 ZOOM_options ZOOM_options_create_with_parent (ZOOM_options parent);
792 void ZOOM_options_destroy (ZOOM_options opt);
795 const char *ZOOM_options_get (ZOOM_options opt, const char *name);
797 void ZOOM_options_set (ZOOM_options opt, const char *name,
801 typedef const char *(*ZOOM_options_callback)
802 (void *handle, const char *name);
804 ZOOM_options_callback
805 ZOOM_options_set_callback (ZOOM_options opt,
806 ZOOM_options_callback c,
810 <sect1 id="zoom.events"><title>Events</title>
812 If you're developing non-blocking applications, you have to deal
816 int ZOOM_event (int no, ZOOM_connection *cs);
819 The <function>ZOOM_event</function> executes pending events for
820 a number of connections. Supply the number of connections in
821 <literal>no</literal> and an array of connections in
822 <literal>cs</literal> (<literal>cs[0] ... cs[no-1]</literal>).
823 A pending event could be a sending a search, receiving a response,
825 When an event has occurred for one of the connections, this function
826 returns a positive integer <literal>n</literal> denoting that an event
827 occurred for connection <literal>cs[n-1]</literal>.
828 When no events are pending for the connections, a value of zero is
830 To ensure that all outstanding requests are performed call this function
831 repeatedly until zero is returned.
836 <!-- Keep this comment at the end of the file
841 sgml-minimize-attributes:nil
842 sgml-always-quote-attributes:t
845 sgml-parent-document: "yaz.xml"
846 sgml-local-catalogs: nil
847 sgml-namecase-general:t