1 <!-- $Id: tools.xml,v 1.23 2003-05-22 16:57:28 mike Exp $ -->
2 <chapter id="tools"><title>Supporting Tools</title>
5 In support of the service API - primarily the ASN module, which
6 provides the pro-grammatic interface to the Z39.50 APDUs, &yaz; contains
7 a collection of tools that support the development of applications.
10 <sect1 id="tools.query"><title>Query Syntax Parsers</title>
13 Since the type-1 (RPN) query structure has no direct, useful string
14 representation, every origin application needs to provide some form of
15 mapping from a local query notation or representation to a
16 <token>Z_RPNQuery</token> structure. Some programmers will prefer to
17 construct the query manually, perhaps using
18 <function>odr_malloc()</function> to simplify memory management.
19 The &yaz; distribution includes two separate, query-generating tools
20 that may be of use to you.
23 <sect2 id="PQF"><title>Prefix Query Format</title>
26 Since RPN or reverse polish notation is really just a fancy way of
27 describing a suffix notation format (operator follows operands), it
28 would seem that the confusion is total when we now introduce a prefix
29 notation for RPN. The reason is one of simple laziness - it's somewhat
30 simpler to interpret a prefix format, and this utility was designed
31 for maximum simplicity, to provide a baseline representation for use
32 in simple test applications and scripting environments (like Tcl). The
33 demonstration client included with YAZ uses the PQF.
38 The PQF have been adopted by other parties developing Z39.50
39 software. It is often referred to as Prefix Query Notation
44 The PQF is defined by the pquery module in the YAZ library.
45 There are two sets of function that have similar behavior. First
46 set operates on a PQF parser handle, second set doesn't. First set
47 set of functions are more flexible than the second set. Second set
48 is obsolete and is only provided to ensure backwards compatibility.
51 First set of functions all operate on a PQF parser handle:
54 #include <yaz/pquery.h>
56 YAZ_PQF_Parser yaz_pqf_create (void);
58 void yaz_pqf_destroy (YAZ_PQF_Parser p);
60 Z_RPNQuery *yaz_pqf_parse (YAZ_PQF_Parser p, ODR o, const char *qbuf);
62 Z_AttributesPlusTerm *yaz_pqf_scan (YAZ_PQF_Parser p, ODR o,
63 Odr_oid **attributeSetId, const char *qbuf);
66 int yaz_pqf_error (YAZ_PQF_Parser p, const char **msg, size_t *off);
69 A PQF parser is created and destructed by functions
70 <function>yaz_pqf_create</function> and
71 <function>yaz_pqf_destroy</function> respectively.
72 Function <function>yaz_pqf_parse</function> parses query given
73 by string <literal>qbuf</literal>. If parsing was successful,
74 a Z39.50 RPN Query is returned which is created using ODR stream
75 <literal>o</literal>. If parsing failed, a NULL pointer is
77 Function <function>yaz_pqf_scan</function> takes a scan query in
78 <literal>qbuf</literal>. If parsing was successful, the function
79 returns attributes plus term pointer and modifies
80 <literal>attributeSetId</literal> to hold attribute set for the
81 scan request - both allocated using ODR stream <literal>o</literal>.
82 If parsing failed, yaz_pqf_scan returns a NULL pointer.
83 Error information for bad queries can be obtained by a call to
84 <function>yaz_pqf_error</function> which returns an error code and
85 modifies <literal>*msg</literal> to point to an error description,
86 and modifies <literal>*off</literal> to the offset within last
87 query were parsing failed.
90 The second set of functions are declared as follows:
93 #include <yaz/pquery.h>
95 Z_RPNQuery *p_query_rpn (ODR o, oid_proto proto, const char *qbuf);
97 Z_AttributesPlusTerm *p_query_scan (ODR o, oid_proto proto,
98 Odr_oid **attributeSetP, const char *qbuf);
100 int p_query_attset (const char *arg);
103 The function <function>p_query_rpn()</function> takes as arguments an
104 &odr; stream (see section <link linkend="odr">The ODR Module</link>)
105 to provide a memory source (the structure created is released on
106 the next call to <function>odr_reset()</function> on the stream), a
107 protocol identifier (one of the constants <token>PROTO_Z3950</token> and
108 <token>PROTO_SR</token>), an attribute set reference, and
109 finally a null-terminated string holding the query string.
112 If the parse went well, <function>p_query_rpn()</function> returns a
113 pointer to a <literal>Z_RPNQuery</literal> structure which can be
114 placed directly into a <literal>Z_SearchRequest</literal>.
115 If parsing failed, due to syntax error, a NULL pointer is returned.
118 The <literal>p_query_attset</literal> specifies which attribute set
119 to use if the query doesn't specify one by the
120 <literal>@attrset</literal> operator.
121 The <literal>p_query_attset</literal> returns 0 if the argument is a
122 valid attribute set specifier; otherwise the function returns -1.
126 The grammar of the PQF is as follows:
130 query ::= top-set query-struct.
132 top-set ::= [ '@attrset' string ]
134 query-struct ::= attr-spec | simple | complex | '@term' term-type
136 attr-spec ::= '@attr' [ string ] string query-struct
138 complex ::= operator query-struct query-struct.
140 operator ::= '@and' | '@or' | '@not' | '@prox' proximity.
142 simple ::= result-set | term.
144 result-set ::= '@set' string.
148 proximity ::= exclusion distance ordered relation which-code unit-code.
150 exclusion ::= '1' | '0' | 'void'.
152 distance ::= integer.
154 ordered ::= '1' | '0'.
156 relation ::= integer.
158 which-code ::= 'known' | 'private' | integer.
160 unit-code ::= integer.
162 term-type ::= 'general' | 'numeric' | 'string' | 'oid' | 'datetime' | 'null'.
166 You will note that the syntax above is a fairly faithful
167 representation of RPN, except for the Attribute, which has been
168 moved a step away from the term, allowing you to associate one or more
169 attributes with an entire query structure. The parser will
170 automatically apply the given attributes to each term as required.
174 The @attr operator is followed by an attribute specification
175 (<literal>attr-spec</literal> above). The specification consists
176 of optional an attribute set, an attribute type-value pair and
177 a sub query. The attribute type-value pair is packed in one string:
178 an attribute type, a dash, followed by an attribute value.
179 The type is always an integer but the value may be either an
180 integer or a string (if it doesn't start with a digit character).
184 Version 3 of the Z39.50 specification defines various encoding of terms.
185 Use <literal>@term </literal> <replaceable>type</replaceable>
186 <replaceable>string</replaceable>,
187 where type is one of: <literal>general</literal>,
188 <literal>numeric</literal> or <literal>string</literal>
189 (for InternationalString).
190 If no term type has been given, the <literal>general</literal> form
191 is used. This is the only encoding allowed in both versions 2 and 3
192 of the Z39.50 standard.
195 <sect3 id="PQF-prox">
196 <title>Using Proximity Operators with PQF</title>
199 This is an advanced topic, describing how to construct
200 queries that make very specific requirements on the
201 relative location of their operands.
202 You may wish to skip this section and go straight to
203 <link linkend="pqf-examples">the example PQF queries</link>.
208 Most Z39.50 servers do not support proximity searching, or
209 support only a small subset of the full functionality that
210 can be expressed using the PQF proximity operator. Be
211 aware that the ability to <emphasis>express</emphasis> a
212 query in PQF is no guarantee that any given server will
213 be able to <emphasis>execute</emphasis> it.
219 The proximity operator <literal>@prox</literal> is a special
220 and more restrictive version of the conjunction operator
221 <literal>@and</literal>. Its semantics are described in
222 section 3.7.2 (Proximity) of Z39.50 the standard itself, which
223 can be read on-line at
224 <ulink url="http://lcweb.loc.gov/z3950/agency/markup/09.html"/>
227 In PQF, the proximity operation is represented by a sequence
230 @prox <replaceable>exclusion</replaceable> <replaceable>distance</replaceable> <replaceable>ordered</replaceable> <replaceable>relation</replaceable> <replaceable>which-code</replaceable> <replaceable>unit-code</replaceable>
232 in which the meanings of the parameters are as described in in
233 the standard, and they can take the following values:
235 <listitem><formalpara><title>exclusion</title><para>
236 0 = false (i.e. the proximity condition specified by the
237 remaining parameters must be satisfied) or
238 1 = true (the proximity condition specified by the
239 remaining parameters must <emphasis>not</emphasis> be
241 </para></formalpara></listitem>
242 <listitem><formalpara><title>distance</title><para>
243 An integer specifying the difference between the locations
244 of the operands: e.g. two adjacent words would have
245 distance=1 since their locations differ by one unit.
246 </para></formalpara></listitem>
247 <listitem><formalpara><title>ordered</title><para>
248 1 = ordered (the operands must occur in the order the
249 query specifies them) or
250 0 = unordered (they may appear in either order).
251 </para></formalpara></listitem>
252 <listitem><formalpara><title>relation</title><para>
253 Recognised values are
257 4 (greaterThanOrEqual),
260 </para></formalpara></listitem>
261 <listitem><formalpara><title>which-code</title><para>
262 <literal>known</literal>
265 (the unit-code parameter is taken from the well-known list
266 of alternatives described in below) or
267 <literal>private</literal>
270 (the unit-code paramater has semantics specific to an
271 out-of-band agreement such as a profile).
272 </para></formalpara></listitem>
273 <listitem><formalpara><title>unit-code</title><para>
274 If the which-code parameter is <literal>known</literal>
275 then the recognised values are
287 If which-code is <literal>private</literal> then the
288 acceptable values are determined by the profile.
289 </para></formalpara></listitem>
291 (The numeric values of the relation and well-known unit-code
292 parameters are taken straight from
293 <ulink url="http://lcweb.loc.gov/z3950/agency/asn1.html#ProximityOperator"
294 >the ASN.1</ulink> of the proximity structure in the standard.)
298 <sect3 id="pqf-examples"><title>PQF queries</title>
300 <para>Queries using simple terms.
306 <para>Boolean operators.
308 @or "dylan" "zimmerman"
309 @and @or dylan zimmerman when
310 @and when @or dylan zimmerman
314 Reference to result sets.
321 Attributes for terms.
324 @attr 1=4 @attr 4=1 "self portrait"
325 @attr exp1 @attr 1=1 CategoryList
326 @attr gils 1=2008 Copenhagen
327 @attr 1=/book/title computer
333 @prox 0 3 1 2 k 2 dylan zimmerman
336 Here the parameters 0, 3, 1, 2, k and 2 represent exclusion,
337 distance, ordered, relation, which-code and unit-code, in that
341 exclusion = 0: the proximity condition must hold
344 distance = 3: the terms must be three units apart
347 ordered = 1: they must occur in the order they are specified
350 relation = 2: lessThanOrEqual (to the distance of 3 units)
353 which-code is ``known'', so the standard unit-codes are used
359 So the whole proximity query means that the words
360 <literal>dylan</literal> and <literal>zimmerman</literal> must
361 both occur in the record, in that order, differing in position
362 by three or fewer words (i.e. with two or fewer words between
363 them.) The query would find ``Bob Dylan, aka. Robert
364 Zimmerman'', but not ``Bob Dylan, born as Robert Zimmerman''
365 since the distance in this case is four.
369 Specifying term type.
371 @term string "a UTF-8 string, maybe?"
376 @or @and bob dylan @set Result-1
378 @attr 4=1 @and @attr 1=1 "bob dylan" @attr 1=4 "slow train coming"
380 @and @attr 2=4 @attr gils 1=2038 -114 @attr 2=2 @attr gils 1=2039 -109
384 The last of these examples is a spatial search: in
385 <ulink url="http://www.gils.net/prof_v2.html#sec_7_4"
386 >the GILS attribute set</ulink>,
388 2038 indicates West Bounding Coordinate and
389 2030 indicates East Bounding Coordinate,
390 so the query is for areas extending from -114 degrees
391 to no more than -109 degrees.
397 <sect2 id="CCL"><title>Common Command Language</title>
400 Not all users enjoy typing in prefix query structures and numerical
401 attribute values, even in a minimalistic test client. In the library
402 world, the more intuitive Common Command Language (or ISO 8777) has
403 enjoyed some popularity - especially before the widespread
404 availability of graphical interfaces. It is still useful in
405 applications where you for some reason or other need to provide a
406 symbolic language for expressing boolean query structures.
410 The <ulink url="http://europagate.dtv.dk/">EUROPAGATE</ulink>
411 research project working under the Libraries programme
412 of the European Commission's DG XIII has, amongst other useful tools,
413 implemented a general-purpose CCL parser which produces an output
414 structure that can be trivially converted to the internal RPN
415 representation of &yaz; (The <literal>Z_RPNQuery</literal> structure).
416 Since the CCL utility - along with the rest of the software
417 produced by EUROPAGATE - is made freely available on a liberal
418 license, it is included as a supplement to &yaz;.
421 <sect3><title>CCL Syntax</title>
424 The CCL parser obeys the following grammar for the FIND argument.
425 The syntax is annotated by in the lines prefixed by
426 <literal>‐‐</literal>.
430 CCL-Find ::= CCL-Find Op Elements
433 Op ::= "and" | "or" | "not"
434 -- The above means that Elements are separated by boolean operators.
436 Elements ::= '(' CCL-Find ')'
439 | Qualifiers Relation Terms
440 | Qualifiers Relation '(' CCL-Find ')'
441 | Qualifiers '=' string '-' string
442 -- Elements is either a recursive definition, a result set reference, a
443 -- list of terms, qualifiers followed by terms, qualifiers followed
444 -- by a recursive definition or qualifiers in a range (lower - upper).
446 Set ::= 'set' = string
447 -- Reference to a result set
449 Terms ::= Terms Prox Term
451 -- Proximity of terms.
455 -- This basically means that a term may include a blank
457 Qualifiers ::= Qualifiers ',' string
459 -- Qualifiers is a list of strings separated by comma
461 Relation ::= '=' | '>=' | '<=' | '<>' | '>' | '<'
462 -- Relational operators. This really doesn't follow the ISO8777
466 -- Proximity operator
470 <example><title>CCL queries</title>
472 The following queries are all valid:
484 (dylan and bob) or set=1
488 Assuming that the qualifiers <literal>ti</literal>,
489 <literal>au</literal>
490 and <literal>date</literal> are defined we may use:
496 au=(bob dylan and slow train coming)
498 date>1980 and (ti=((self portrait)))
504 <sect3><title>CCL Qualifiers</title>
507 Qualifiers are used to direct the search to a particular searchable
508 index, such as title (ti) and author indexes (au). The CCL standard
509 itself doesn't specify a particular set of qualifiers, but it does
510 suggest a few short-hand notations. You can customize the CCL parser
511 to support a particular set of qualifiers to reflect the current target
512 profile. Traditionally, a qualifier would map to a particular
513 use-attribute within the BIB-1 attribute set. However, you could also
514 define qualifiers that would set, for example, the
519 A CCL profile is a set of predefined CCL qualifiers that may be
521 The YAZ client reads its CCL qualifiers from a file named
522 <filename>default.bib</filename>. Each line in the file has the form:
526 <replaceable>qualifier-name</replaceable>
527 [<replaceable>attributeset</replaceable><literal>,</literal>]<replaceable>type</replaceable><literal>=</literal><replaceable>val</replaceable>
528 [<replaceable>attributeset</replaceable><literal>,</literal>]<replaceable>type</replaceable><literal>=</literal><replaceable>val</replaceable> ...
532 where <replaceable>qualifier-name</replaceable> is the name of the
533 qualifier to be used (eg. <literal>ti</literal>),
534 <replaceable>type</replaceable> is attribute type in the attribute
535 set (Bib-1 is used if no attribute set is given) and
536 <replaceable>val</replaceable> is attribute value.
537 The <replaceable>type</replaceable> can be specified as an
538 integer or as it be specified either as a single-letter:
539 <literal>u</literal> for use,
540 <literal>r</literal> for relation,<literal>p</literal> for position,
541 <literal>s</literal> for structure,<literal>t</literal> for truncation
542 or <literal>c</literal> for completeness.
543 The attributes for the special qualifier name <literal>term</literal>
544 are used when no CCL qualifier is given in a query.
547 <example><title>CCL profile</title>
549 Consider the following definition:
559 Three qualifiers are defined, <literal>ti</literal>,
560 <literal>au</literal> and <literal>ranked</literal>.
561 <literal>ti</literal> and <literal>au</literal> both set
562 structure attribute to phrase (s=1).
563 <literal>ti</literal>
564 sets the use-attribute to 4. <literal>au</literal> sets the
566 When no qualifiers are used in the query the structure-attribute is
567 set to free-form-text (105).
570 You can combine attributes. To Search for "ranked title" you
573 ti,ranked=knuth computer
575 which will use "relation is ranked", "use is title", "structure is
581 <sect3><title>CCL API</title>
583 All public definitions can be found in the header file
584 <filename>ccl.h</filename>. A profile identifier is of type
585 <literal>CCL_bibset</literal>. A profile must be created with the call
586 to the function <function>ccl_qual_mk</function> which returns a profile
587 handle of type <literal>CCL_bibset</literal>.
591 To read a file containing qualifier definitions the function
592 <function>ccl_qual_file</function> may be convenient. This function
593 takes an already opened <literal>FILE</literal> handle pointer as
594 argument along with a <literal>CCL_bibset</literal> handle.
598 To parse a simple string with a FIND query use the function
601 struct ccl_rpn_node *ccl_find_str (CCL_bibset bibset, const char *str,
602 int *error, int *pos);
605 which takes the CCL profile (<literal>bibset</literal>) and query
606 (<literal>str</literal>) as input. Upon successful completion the RPN
607 tree is returned. If an error occur, such as a syntax error, the integer
608 pointed to by <literal>error</literal> holds the error code and
609 <literal>pos</literal> holds the offset inside query string in which
614 An English representation of the error may be obtained by calling
615 the <literal>ccl_err_msg</literal> function. The error codes are
616 listed in <filename>ccl.h</filename>.
620 To convert the CCL RPN tree (type
621 <literal>struct ccl_rpn_node *</literal>)
622 to the Z_RPNQuery of YAZ the function <function>ccl_rpn_query</function>
623 must be used. This function which is part of YAZ is implemented in
624 <filename>yaz-ccl.c</filename>.
625 After calling this function the CCL RPN tree is probably no longer
626 needed. The <literal>ccl_rpn_delete</literal> destroys the CCL RPN tree.
630 A CCL profile may be destroyed by calling the
631 <function>ccl_qual_rm</function> function.
635 The token names for the CCL operators may be changed by setting the
636 globals (all type <literal>char *</literal>)
637 <literal>ccl_token_and</literal>, <literal>ccl_token_or</literal>,
638 <literal>ccl_token_not</literal> and <literal>ccl_token_set</literal>.
639 An operator may have aliases, i.e. there may be more than one name for
640 the operator. To do this, separate each alias with a space character.
644 <sect2 id="tools.cql"><title>CQL</title>
646 <ulink url="http://www.loc.gov/z3950/agency/zing/cql/">CQL</ulink>
647 - Common Query Language - was defined for the
648 <ulink url="http://www.loc.gov/z3950/agency/zing/srw/">SRW</ulink>
650 In many ways CQL has a similar syntax to CCL.
651 The objective of CQL is different. Where CCL aims to be
652 an end-user language, CQL is <emphasis>the</emphasis> protocol
653 query language for SRW.
657 If you are new to CQL, read the
658 <ulink url="http://zing.z3950.org/cql/intro.html">Gentle
659 Introduction</ulink>.
663 The CQL parser in &yaz; provides the following:
667 It parses and validates a CQL query.
672 It generates a C structure that allows you to convert
673 a CQL query to some other query language, such as SQL.
678 The parser converts a valid CQL query to PQF, thus providing a
679 way to use CQL for both SRW/SRU servers and Z39.50 targets at the
685 The parser converts CQL to
686 <ulink url="http://www.loc.gov/z3950/agency/zing/cql/xcql.html">
688 XCQL is an XML representation of CQL.
689 XCQL is part of the SRW specification. However, since SRU
690 supports CQL only, we don't expect XCQL to be widely used.
691 Furthermore, CQL has the advantage over XCQL that it is
697 <sect3 id="tools.cql.parsing"><title>CQL parsing</title>
699 A CQL parser is represented by the <literal>CQL_parser</literal>
700 handle. Its contents should be considered &yaz; internal (private).
702 #include <yaz/cql.h>
704 typedef struct cql_parser *CQL_parser;
706 CQL_parser cql_parser_create(void);
707 void cql_parser_destroy(CQL_parser cp);
709 A parser is created by <function>cql_parser_create</function> and
710 is destroyed by <function>cql_parser_destroy</function>.
713 To parse a CQL query string, the following function
716 int cql_parser_string(CQL_parser cp, const char *str);
718 A CQL query is parsed by the <function>cql_parser_string</function>
719 which takes a query <parameter>str</parameter>.
720 If the query was valid (no syntax errors), then zero is returned;
721 otherwise a non-zero error code is returned.
725 int cql_parser_stream(CQL_parser cp,
726 int (*getbyte)(void *client_data),
727 void (*ungetbyte)(int b, void *client_data),
730 int cql_parser_stdio(CQL_parser cp, FILE *f);
732 The functions <function>cql_parser_stream</function> and
733 <function>cql_parser_stdio</function> parses a CQL query
734 - just like <function>cql_parser_string</function>.
735 The only difference is that the CQL query can be
736 fed to the parser in different ways.
737 The <function>cql_parser_stream</function> uses a generic
738 byte stream as input. The <function>cql_parser_stdio</function>
739 uses a <literal>FILE</literal> handle which is opened for reading.
743 <sect3 id="tools.cql.tree"><title>CQL tree</title>
745 The the query string is validl, the CQL parser
746 generates a tree representing the structure of the
751 struct cql_node *cql_parser_result(CQL_parser cp);
753 <function>cql_parser_result</function> returns the
754 a pointer to the root node of the resulting tree.
757 Each node in a CQL tree is represented by a
758 <literal>struct cql_node</literal>.
759 It is defined as follows:
761 #define CQL_NODE_ST 1
762 #define CQL_NODE_BOOL 2
763 #define CQL_NODE_MOD 3
771 struct cql_node *modifiers;
772 struct cql_node *prefixes;
776 struct cql_node *left;
777 struct cql_node *right;
778 struct cql_node *modifiers;
779 struct cql_node *prefixes;
784 struct cql_node *next;
789 There are three kinds of nodes, search term (ST), boolean (BOOL),
793 The search term node has five members:
797 <literal>index</literal>: index for search term.
798 If an index is unspecified for a search term,
799 <literal>index</literal> will be NULL.
804 <literal>term</literal>: the search term itself.
809 <literal>relation</literal>: relation for search term.
814 <literal>modifiers</literal>: relation modifiers for search
815 term. The <literal>modifiers</literal> is a simple linked
816 list (NULL for last entry). Each relation modifier node
817 is of type <literal>MOD</literal>.
822 <literal>prefixes</literal>: index prefixes for search
823 term. The <literal>prefixes</literal> is a simple linked
824 list (NULL for last entry). Each prefix node
825 is of type <literal>MOD</literal>.
832 The boolean node represents both <literal>and</literal>,
833 <literal>or</literal>, not as well as
838 <literal>left</literal> and <literal>right</literal>: left
839 - and right operand respectively.
844 <literal>modifiers</literal>: proximity arguments.
849 <literal>prefixes</literal>: index prefixes.
850 The <literal>prefixes</literal> is a simple linked
851 list (NULL for last entry). Each prefix node
852 is of type <literal>MOD</literal>.
859 The modifier node is a "utility" node used for name-value pairs,
860 such as prefixes, proximity arguements, etc.
864 <literal>name</literal> name of mod node.
869 <literal>value</literal> value of mod node.
874 <literal>next</literal>: pointer to next node which is
875 always a mod node (NULL for last entry).
882 <sect3 id="tools.cql.pqf"><title>CQL to PQF conversion</title>
884 Conversion to PQF (and Z39.50 RPN) is tricky by the fact
885 that the resulting RPN depends on the Z39.50 target
886 capabilities (combinations of supported attributes).
887 In addition, the CQL and SRW operates on index prefixes
888 (URI or strings), whereas the RPN uses Object Identifiers
892 The CQL library of &yaz; defines a <literal>cql_transform_t</literal>
893 type. It represents a particular mapping between CQL and RPN.
894 This handle is created and destroyed by the functions:
896 cql_transform_t cql_transform_open_FILE (FILE *f);
897 cql_transform_t cql_transform_open_fname(const char *fname);
898 void cql_transform_close(cql_transform_t ct);
900 The first two functions create a tranformation handle from
901 either an already open FILE or from a filename respectively.
904 The handle is destroyed by <function>cql_transform_close</function>
905 in which case no further reference of the handle is allowed.
908 When a <literal>cql_transform_t</literal> handle has been created
909 you can convert to RPN.
911 int cql_transform_buf(cql_transform_t ct,
912 struct cql_node *cn, char *out, int max);
914 This function converts the CQL tree <literal>cn</literal>
915 using handle <literal>ct</literal>.
916 For the resulting PQF, you supply a buffer <literal>out</literal>
917 which must be able to hold at at least <literal>max</literal>
921 If conversion failed, <function>cql_transform_buf</function>
922 returns a non-zero SRW error code; otherwise zero is returned
923 (conversion successful). The meanings of the numeric error
924 codes are listed in the SRW specifications at
925 <ulink url="http://www.loc.gov/srw/diagnostic-list.html"/>
928 If conversion fails, more information can be obtained by calling
930 int cql_transform_error(cql_transform_t ct, char **addinfop);
932 This function returns the most recently returned numeric
933 error-code and sets the string-pointer at
934 <literal>*addinfop</literal> to point to a string containing
935 additional information about the error that occurred: for
936 example, if the error code is 15 (``Illegal or unsupported index
937 set''), the additional information is the name of the requested
938 index set that was not recognised.
941 If you wish to be able to produce a PQF result in a different
942 way, there are two alternatives.
944 void cql_transform_pr(cql_transform_t ct,
946 void (*pr)(const char *buf, void *client_data),
949 int cql_transform_FILE(cql_transform_t ct,
950 struct cql_node *cn, FILE *f);
952 The former function produces output to a user-defined
953 output stream. The latter writes the result to an already
954 open <literal>FILE</literal>.
957 <sect3 id="tools.cql.map">
958 <title>Specification of CQL to RPN mapping</title>
960 The file supplied to functions
961 <function>cql_transform_open_FILE</function>,
962 <function>cql_transform_open_fname</function> follows
963 a structure found in many Unix utilities.
964 It consists of mapping specifications - one per line.
965 Lines starting with <literal>#</literal> are ignored (comments).
968 Each line is of the form
970 <replaceable>CQL pattern</replaceable><literal> = </literal> <replaceable> RPN equivalent</replaceable>
974 An RPN pattern is a simple attribute list. Each attribute pair
977 [<replaceable>set</replaceable>] <replaceable>type</replaceable><literal>=</literal><replaceable>value</replaceable>
979 The attribute <replaceable>set</replaceable> is optional.
980 The <replaceable>type</replaceable> is the attribute type,
981 <replaceable>value</replaceable> the attribute value.
984 The following CQL patterns are recognized:
987 <literal>qualifier.</literal><replaceable>set</replaceable><literal>.</literal><replaceable>name</replaceable>
991 This pattern is invoked when a CQL qualifier, such as
992 dc.title is converted. <replaceable>set</replaceable>
993 and <replaceable>name</replaceable> is the index set and qualifier
995 Typically, the RPN specifies an equivalent use attribute.
998 For terms not bound by a qualifier the pattern
999 <literal>qualifier.srw.serverChoice</literal> is used.
1000 Here, the prefix <literal>srw</literal> is defined as
1001 <literal>http://www.loc.gov/zing/cql/srw-indexes/v1.0/</literal>.
1002 If this pattern is not defined, the mapping will fail.
1006 <varlistentry><term>
1007 <literal>relation.</literal><replaceable>relation</replaceable>
1011 This pattern specifies how a CQL relation is mapped to RPN.
1012 <replaceable>pattern</replaceable> is name of relation
1013 operator. Since <literal>=</literal> is used as
1014 separator between CQL pattern and RPN, CQL relations
1015 including <literal>=</literal> cannot be
1016 used directly. To avoid a conflict, the names
1017 <literal>ge</literal>,
1018 <literal>eq</literal>,
1019 <literal>le</literal>,
1020 must be used for CQL operators, greater-than-or-equal,
1021 equal, less-than-or-equal respectively.
1022 The RPN pattern is supposed to include a relation attribute.
1025 For terms not bound by a relation, the pattern
1026 <literal>relation.scr</literal> is used. If the pattern
1027 is not defined, the mapping will fail.
1030 The special pattern, <literal>relation.*</literal> is used
1031 when no other relation pattern is matched.
1036 <varlistentry><term>
1037 <literal>relationModifier.</literal><replaceable>mod</replaceable>
1041 This pattern specifies how a CQL relation modifier is mapped to RPN.
1042 The RPN pattern is usually a relation attribute.
1047 <varlistentry><term>
1048 <literal>structure.</literal><replaceable>type</replaceable>
1052 This pattern specifies how a CQL structure is mapped to RPN.
1053 Note that this CQL pattern is somewhat to similar to
1054 CQL pattern <literal>relation</literal>.
1055 The <replaceable>type</replaceable> is a CQL relation.
1058 The pattern, <literal>structure.*</literal> is used
1059 when no other structure pattern is matched.
1060 Usually, the RPN equivalent specifies a structure attribute.
1065 <varlistentry><term>
1066 <literal>position.</literal><replaceable>type</replaceable>
1070 This pattern specifies how the anchor (position) of
1071 CQL is mapped to RPN.
1072 The <replaceable>type</replaceable> is one
1073 of <literal>first</literal>, <literal>any</literal>,
1074 <literal>last</literal>, <literal>firstAndLast</literal>.
1077 The pattern, <literal>position.*</literal> is used
1078 when no other position pattern is matched.
1083 <varlistentry><term>
1084 <literal>set.</literal><replaceable>prefix</replaceable>
1088 This specification defines a CQL index set for a given prefix.
1089 The value on the right hand side is the URI for the set -
1090 <emphasis>not</emphasis> RPN. All prefixes used in
1091 qualifier patterns must be defined this way.
1097 <example><title>CQL to RPN mapping file</title>
1099 This simple file defines two index sets, three qualifiers and three
1100 relations, a position pattern and a default structure.
1102 <programlisting><![CDATA[
1103 set.srw = http://www.loc.gov/zing/cql/srw-indexes/v1.0/
1104 set.dc = http://www.loc.gov/zing/cql/dc-indexes/v1.0/
1106 qualifier.srw.serverChoice = 1=1016
1107 qualifier.dc.title = 1=4
1108 qualifier.dc.subject = 1=21
1114 position.any = 3=3 6=1
1120 With the mappings above, the CQL query
1124 is converted to the PQF:
1126 @attr 1=1016 @attr 2=3 @attr 4=1 @attr 3=3 @attr 6=1 "computer"
1128 by rules <literal>qualifier.srw.serverChoice</literal>,
1129 <literal>relation.scr</literal>, <literal>structure.*</literal>,
1130 <literal>position.any</literal>.
1137 is rejected, since <literal>position.right</literal> is
1143 >my = "http://www.loc.gov/zing/cql/dc-indexes/v1.0/" my.title = x
1147 @attr 1=4 @attr 2=3 @attr 4=1 @attr 3=3 @attr 6=1 "x"
1152 <sect3 id="tools.cql.xcql"><title>CQL to XCQL conversion</title>
1154 Conversion from CQL to XCQL is trivial and does not
1155 require a mapping to be defined.
1156 There three functions to choose from depending on the
1157 way you wish to store the resulting output (XML buffer
1160 int cql_to_xml_buf(struct cql_node *cn, char *out, int max);
1161 void cql_to_xml(struct cql_node *cn,
1162 void (*pr)(const char *buf, void *client_data),
1164 void cql_to_xml_stdio(struct cql_node *cn, FILE *f);
1166 Function <function>cql_to_xml_buf</function> converts
1167 to XCQL and stores result in a user supplied buffer of a given
1171 <function>cql_to_xml</function> writes the result in
1172 a user defined output stream.
1173 <function>cql_to_xml_stdio</function> writes to a
1179 <sect1 id="tools.oid"><title>Object Identifiers</title>
1182 The basic YAZ representation of an OID is an array of integers,
1183 terminated with the value -1. The &odr; module provides two
1184 utility-functions to create and copy this type of data elements:
1188 Odr_oid *odr_getoidbystr(ODR o, char *str);
1192 Creates an OID based on a string-based representation using dots (.)
1193 to separate elements in the OID.
1197 Odr_oid *odr_oiddup(ODR odr, Odr_oid *o);
1201 Creates a copy of the OID referenced by the <emphasis>o</emphasis>
1203 Both functions take an &odr; stream as parameter. This stream is used to
1204 allocate memory for the data elements, which is released on a
1205 subsequent call to <function>odr_reset()</function> on that stream.
1209 The OID module provides a higher-level representation of the
1210 family of object identifiers which describe the Z39.50 protocol and its
1211 related objects. The definition of the module interface is given in
1212 the <filename>oid.h</filename> file.
1216 The interface is mainly based on the <literal>oident</literal> structure.
1217 The definition of this structure looks like this:
1221 typedef struct oident
1226 int oidsuffix[OID_SIZE];
1232 The proto field takes one of the values
1241 If you don't care about talking to SR-based implementations (few
1242 exist, and they may become fewer still if and when the ISO SR and ANSI
1243 Z39.50 documents are merged into a single standard), you can ignore
1244 this field on incoming packages, and always set it to PROTO_Z3950
1245 for outgoing packages.
1249 The oclass field takes one of the values
1271 corresponding to the OID classes defined by the Z39.50 standard.
1273 Finally, the value field takes one of the values
1331 again, corresponding to the specific OIDs defined by the standard.
1335 The desc field contains a brief, mnemonic name for the OID in question.
1343 struct oident *oid_getentbyoid(int *o);
1347 takes as argument an OID, and returns a pointer to a static area
1348 containing an <literal>oident</literal> structure. You typically use
1349 this function when you receive a PDU containing an OID, and you wish
1350 to branch out depending on the specific OID value.
1358 int *oid_ent_to_oid(struct oident *ent, int *dst);
1362 Takes as argument an <literal>oident</literal> structure - in which
1363 the <literal>proto</literal>, <literal>oclass</literal>/, and
1364 <literal>value</literal> fields are assumed to be set correctly -
1365 and returns a pointer to a the buffer as given by <literal>dst</literal>
1367 representation of the corresponding OID. The function returns
1368 NULL and the array dst is unchanged if a mapping couldn't place.
1369 The array <literal>dst</literal> should be at least of size
1370 <literal>OID_SIZE</literal>.
1374 The <function>oid_ent_to_oid()</function> function can be used whenever
1375 you need to prepare a PDU containing one or more OIDs. The separation of
1376 the <literal>protocol</literal> element from the remainder of the
1377 OID-description makes it simple to write applications that can
1378 communicate with either Z39.50 or OSI SR-based applications.
1386 oid_value oid_getvalbyname(const char *name);
1390 takes as argument a mnemonic OID name, and returns the
1391 <literal>/value</literal> field of the first entry in the database that
1392 contains the given name in its <literal>desc</literal> field.
1396 Finally, the module provides the following utility functions, whose
1397 meaning should be obvious:
1401 void oid_oidcpy(int *t, int *s);
1402 void oid_oidcat(int *t, int *s);
1403 int oid_oidcmp(int *o1, int *o2);
1404 int oid_oidlen(int *o);
1409 The OID module has been criticized - and perhaps rightly so
1410 - for needlessly abstracting the
1411 representation of OIDs. Other toolkits use a simple
1412 string-representation of OIDs with good results. In practice, we have
1413 found the interface comfortable and quick to work with, and it is a
1414 simple matter (for what it's worth) to create applications compatible
1415 with both ISO SR and Z39.50. Finally, the use of the
1416 <literal>/oident</literal> database is by no means mandatory.
1417 You can easily create your own system for representing OIDs, as long
1418 as it is compatible with the low-level integer-array representation
1425 <sect1 id="tools.nmem"><title>Nibble Memory</title>
1428 Sometimes when you need to allocate and construct a large,
1429 interconnected complex of structures, it can be a bit of a pain to
1430 release the associated memory again. For the structures describing the
1431 Z39.50 PDUs and related structures, it is convenient to use the
1432 memory-management system of the &odr; subsystem (see
1433 <link linkend="odr-use">Using ODR</link>). However, in some circumstances
1434 where you might otherwise benefit from using a simple nibble memory
1435 management system, it may be impractical to use
1436 <function>odr_malloc()</function> and <function>odr_reset()</function>.
1437 For this purpose, the memory manager which also supports the &odr;
1438 streams is made available in the NMEM module. The external interface
1439 to this module is given in the <filename>nmem.h</filename> file.
1443 The following prototypes are given:
1447 NMEM nmem_create(void);
1448 void nmem_destroy(NMEM n);
1449 void *nmem_malloc(NMEM n, int size);
1450 void nmem_reset(NMEM n);
1451 int nmem_total(NMEM n);
1452 void nmem_init(void);
1453 void nmem_exit(void);
1457 The <function>nmem_create()</function> function returns a pointer to a
1458 memory control handle, which can be released again by
1459 <function>nmem_destroy()</function> when no longer needed.
1460 The function <function>nmem_malloc()</function> allocates a block of
1461 memory of the requested size. A call to <function>nmem_reset()</function>
1462 or <function>nmem_destroy()</function> will release all memory allocated
1463 on the handle since it was created (or since the last call to
1464 <function>nmem_reset()</function>. The function
1465 <function>nmem_total()</function> returns the number of bytes currently
1466 allocated on the handle.
1470 The nibble memory pool is shared amongst threads. POSIX
1471 mutex'es and WIN32 Critical sections are introduced to keep the
1472 module thread safe. Function <function>nmem_init()</function>
1473 initializes the nibble memory library and it is called automatically
1474 the first time the <literal>YAZ.DLL</literal> is loaded. &yaz; uses
1475 function <function>DllMain</function> to achieve this. You should
1476 <emphasis>not</emphasis> call <function>nmem_init</function> or
1477 <function>nmem_exit</function> unless you're absolute sure what
1478 you're doing. Note that in previous &yaz; versions you'd have to call
1479 <function>nmem_init</function> yourself.
1485 <!-- Keep this comment at the end of the file
1490 sgml-minimize-attributes:nil
1491 sgml-always-quote-attributes:t
1494 sgml-parent-document: "yaz.xml"
1495 sgml-local-catalogs: nil
1496 sgml-namecase-general:t