1 <!-- $Id: tools.xml,v 1.17 2003-01-27 21:30:59 adam 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48 is obsolete and is only provided to ensure backwards compatibility.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 Z39.50 version 3 defines various encoding of terms.
185 Use the @term operator to indicate the encoding type:
186 <literal>general</literal>, <literal>numeric</literal>,
187 <literal>string</literal> (for InternationalString), ..
188 If no term type has been given, the <literal>general</literal> form
189 is used which is the only encoding allowed in both version 2 - and 3
190 of the Z39.50 standard.
194 The following are all examples of valid queries in the PQF.
202 @or "dylan" "zimmerman"
206 @or @and bob dylan @set Result-1
210 @attr 4=1 @and @attr 1=1 "bob dylan" @attr 1=4 "slow train coming"
212 @attr 4=1 @attr 1=4 "self portrait"
214 @prox 0 3 1 2 k 2 dylan zimmerman
216 @and @attr 2=4 @attr gils 1=2038 -114 @attr 2=2 @attr gils 1=2039 -109
218 @term string "a UTF-8 string, maybe?"
220 @attr 1=/book/title computer
224 <sect2 id="CCL"><title>Common Command Language</title>
227 Not all users enjoy typing in prefix query structures and numerical
228 attribute values, even in a minimalistic test client. In the library
229 world, the more intuitive Common Command Language (or ISO 8777) has
230 enjoyed some popularity - especially before the widespread
231 availability of graphical interfaces. It is still useful in
232 applications where you for some reason or other need to provide a
233 symbolic language for expressing boolean query structures.
237 The <ulink url="http://europagate.dtv.dk/">EUROPAGATE</ulink>
238 research project working under the Libraries programme
239 of the European Commission's DG XIII has, amongst other useful tools,
240 implemented a general-purpose CCL parser which produces an output
241 structure that can be trivially converted to the internal RPN
242 representation of &yaz; (The <literal>Z_RPNQuery</literal> structure).
243 Since the CCL utility - along with the rest of the software
244 produced by EUROPAGATE - is made freely available on a liberal
245 license, it is included as a supplement to &yaz;.
248 <sect3><title>CCL Syntax</title>
251 The CCL parser obeys the following grammar for the FIND argument.
252 The syntax is annotated by in the lines prefixed by
253 <literal>‐‐</literal>.
257 CCL-Find ::= CCL-Find Op Elements
260 Op ::= "and" | "or" | "not"
261 -- The above means that Elements are separated by boolean operators.
263 Elements ::= '(' CCL-Find ')'
266 | Qualifiers Relation Terms
267 | Qualifiers Relation '(' CCL-Find ')'
268 | Qualifiers '=' string '-' string
269 -- Elements is either a recursive definition, a result set reference, a
270 -- list of terms, qualifiers followed by terms, qualifiers followed
271 -- by a recursive definition or qualifiers in a range (lower - upper).
273 Set ::= 'set' = string
274 -- Reference to a result set
276 Terms ::= Terms Prox Term
278 -- Proximity of terms.
282 -- This basically means that a term may include a blank
284 Qualifiers ::= Qualifiers ',' string
286 -- Qualifiers is a list of strings separated by comma
288 Relation ::= '=' | '>=' | '<=' | '<>' | '>' | '<'
289 -- Relational operators. This really doesn't follow the ISO8777
293 -- Proximity operator
298 The following queries are all valid:
310 (dylan and bob) or set=1
314 Assuming that the qualifiers <literal>ti</literal>, <literal>au</literal>
315 and <literal>date</literal> are defined we may use:
321 au=(bob dylan and slow train coming)
323 date>1980 and (ti=((self portrait)))
328 <sect3><title>CCL Qualifiers</title>
331 Qualifiers are used to direct the search to a particular searchable
332 index, such as title (ti) and author indexes (au). The CCL standard
333 itself doesn't specify a particular set of qualifiers, but it does
334 suggest a few short-hand notations. You can customize the CCL parser
335 to support a particular set of qualifiers to reflect the current target
336 profile. Traditionally, a qualifier would map to a particular
337 use-attribute within the BIB-1 attribute set. However, you could also
338 define qualifiers that would set, for example, the
343 Consider a scenario where the target support ranked searches in the
344 title-index. In this case, the user could specify
348 ti,ranked=knuth computer
351 and the <literal>ranked</literal> would map to relation=relevance
352 (2=102) and the <literal>ti</literal> would map to title (1=4).
356 A "profile" with a set predefined CCL qualifiers can be read from a
357 file. The YAZ client reads its CCL qualifiers from a file named
358 <filename>default.bib</filename>. Each line in the file has the form:
362 <replaceable>qualifier-name</replaceable>
363 <replaceable>type</replaceable>=<replaceable>val</replaceable>
364 <replaceable>type</replaceable>=<replaceable>val</replaceable> ...
368 where <replaceable>qualifier-name</replaceable> is the name of the
369 qualifier to be used (eg. <literal>ti</literal>),
370 <replaceable>type</replaceable> is a BIB-1 category type and
371 <replaceable>val</replaceable> is the corresponding BIB-1 attribute
373 The <replaceable>type</replaceable> can be either numeric or it may be
374 either <literal>u</literal> (use), <literal>r</literal> (relation),
375 <literal>p</literal> (position), <literal>s</literal> (structure),
376 <literal>t</literal> (truncation) or <literal>c</literal> (completeness).
377 The <replaceable>qualifier-name</replaceable> <literal>term</literal>
378 has a special meaning.
379 The types and values for this definition is used when
380 <emphasis>no</emphasis> qualifiers are present.
384 Consider the following definition:
393 Two qualifiers are defined, <literal>ti</literal> and
394 <literal>au</literal>.
395 They both set the structure-attribute to phrase (1).
396 <literal>ti</literal>
397 sets the use-attribute to 4. <literal>au</literal> sets the
399 When no qualifiers are used in the query the structure-attribute is
400 set to free-form-text (105).
404 <sect3><title>CCL API</title>
406 All public definitions can be found in the header file
407 <filename>ccl.h</filename>. A profile identifier is of type
408 <literal>CCL_bibset</literal>. A profile must be created with the call
409 to the function <function>ccl_qual_mk</function> which returns a profile
410 handle of type <literal>CCL_bibset</literal>.
414 To read a file containing qualifier definitions the function
415 <function>ccl_qual_file</function> may be convenient. This function
416 takes an already opened <literal>FILE</literal> handle pointer as
417 argument along with a <literal>CCL_bibset</literal> handle.
421 To parse a simple string with a FIND query use the function
424 struct ccl_rpn_node *ccl_find_str (CCL_bibset bibset, const char *str,
425 int *error, int *pos);
428 which takes the CCL profile (<literal>bibset</literal>) and query
429 (<literal>str</literal>) as input. Upon successful completion the RPN
430 tree is returned. If an error occur, such as a syntax error, the integer
431 pointed to by <literal>error</literal> holds the error code and
432 <literal>pos</literal> holds the offset inside query string in which
437 An English representation of the error may be obtained by calling
438 the <literal>ccl_err_msg</literal> function. The error codes are
439 listed in <filename>ccl.h</filename>.
443 To convert the CCL RPN tree (type
444 <literal>struct ccl_rpn_node *</literal>)
445 to the Z_RPNQuery of YAZ the function <function>ccl_rpn_query</function>
446 must be used. This function which is part of YAZ is implemented in
447 <filename>yaz-ccl.c</filename>.
448 After calling this function the CCL RPN tree is probably no longer
449 needed. The <literal>ccl_rpn_delete</literal> destroys the CCL RPN tree.
453 A CCL profile may be destroyed by calling the
454 <function>ccl_qual_rm</function> function.
458 The token names for the CCL operators may be changed by setting the
459 globals (all type <literal>char *</literal>)
460 <literal>ccl_token_and</literal>, <literal>ccl_token_or</literal>,
461 <literal>ccl_token_not</literal> and <literal>ccl_token_set</literal>.
462 An operator may have aliases, i.e. there may be more than one name for
463 the operator. To do this, separate each alias with a space character.
467 <sect2 id="tools.cql"><title>CQL</title>
469 <ulink url="http://www.loc.gov/z3950/agency/zing/cql/">CQL</ulink>
470 - Common Query Language - was defined for the
471 <ulink url="http://www.loc.gov/z3950/agency/zing/srw/">SRW</ulink>
473 In many ways CQL has a similar syntax to CCL.
474 The objective of CQL is different. Where CCL aims to be
475 an end-user language, CQL is <emphasis>the</emphasis> protocol
476 query language for SRW.
480 If you are new to CQL, read the
481 <ulink url="http://zing.z3950.org/cql/intro.html">Gentle
482 Introduction</ulink>.
486 The CQL parser in &yaz; provides the following:
490 It parses and validates a CQL query.
495 It generates a C structure that allows you to convert
496 a CQL query to some other query language, such as SQL.
501 The parser converts a valid CQL query to PQF, thus providing a
502 way to use CQL for both SRW/SRU servers and Z39.50 targets at the
508 The parser converts CQL to
509 <ulink url="http://www.loc.gov/z3950/agency/zing/cql/xcql.html">
511 XCQL is an XML representation of CQL.
512 XCQL is part of the SRW specification. However, since SRU
513 supports CQL only, we don't expect XCQL to be widely used.
514 Furthermore, CQL has the advantage over XCQL that it is
520 <sect3 id="tools.cql.parsing"><title>CQL parsing</title>
522 A CQL parser is represented by the <literal>CQL_parser</literal>
523 handle. Its contents should be considered &yaz; internal (private).
525 #include <yaz/cql.h>
527 typedef struct cql_parser *CQL_parser;
529 CQL_parser cql_parser_create(void);
530 void cql_parser_destroy(CQL_parser cp);
532 A parser is created by <function>cql_parser_create</function> and
533 is destroyed by <function>cql_parser_destroy</function>.
536 To parse a CQL query string, the following function
539 int cql_parser_string(CQL_parser cp, const char *str);
541 A CQL query is parsed by the <function>cql_parser_string</function>
542 which takes a query <parameter>str</parameter>.
543 If the query was valid (no syntax errors), then zero is returned;
544 otherwise a non-zero error code is returned.
548 int cql_parser_stream(CQL_parser cp,
549 int (*getbyte)(void *client_data),
550 void (*ungetbyte)(int b, void *client_data),
553 int cql_parser_stdio(CQL_parser cp, FILE *f);
555 The functions <function>cql_parser_stream</function> and
556 <function>cql_parser_stdio</function> parses a CQL query
557 - just like <function>cql_parser_string</function>.
558 The only difference is that the CQL query can be
559 fed to the parser in different ways.
560 The <function>cql_parser_stream</function> uses a generic
561 byte stream as input. The <function>cql_parser_stdio</function>
562 uses a <literal>FILE</literal> handle which is opened for reading.
566 <sect3 id="tools.cql.tree"><title>CQL tree</title>
568 The the query string is validl, the CQL parser
569 generates a tree representing the structure of the
574 struct cql_node *cql_parser_result(CQL_parser cp);
576 <function>cql_parser_result</function> returns the
577 a pointer to the root node of the resulting tree.
580 Each node in a CQL tree is represented by a
581 <literal>struct cql_node</literal>.
582 It is defined as follows:
584 #define CQL_NODE_ST 1
585 #define CQL_NODE_BOOL 2
586 #define CQL_NODE_MOD 3
594 struct cql_node *modifiers;
595 struct cql_node *prefixes;
599 struct cql_node *left;
600 struct cql_node *right;
601 struct cql_node *modifiers;
602 struct cql_node *prefixes;
607 struct cql_node *next;
612 There are three kinds of nodes, search term (ST), boolean (BOOL),
616 The search term node has five members:
620 <literal>index</literal>: index for search term.
621 If an index is unspecified for a search term,
622 <literal>index</literal> will be NULL.
627 <literal>term</literal>: the search term itself.
632 <literal>relation</literal>: relation for search term.
637 <literal>modifiers</literal>: relation modifiers for search
638 term. The <literal>modifiers</literal> is a simple linked
639 list (NULL for last entry). Each relation modifier node
640 is of type <literal>MOD</literal>.
645 <literal>prefixes</literal>: index prefixes for search
646 term. The <literal>prefixes</literal> is a simple linked
647 list (NULL for last entry). Each prefix node
648 is of type <literal>MOD</literal>.
655 The boolean node represents both <literal>and</literal>,
656 <literal>or</literal>, not as well as
661 <literal>left</literal> and <literal>right</literal>: left
662 - and right operand respectively.
667 <literal>modifiers</literal>: proximity arguments.
672 <literal>prefixes</literal>: index prefixes.
673 The <literal>prefixes</literal> is a simple linked
674 list (NULL for last entry). Each prefix node
675 is of type <literal>MOD</literal>.
682 The modifier node is a "utility" node used for name-value pairs,
683 such as prefixes, proximity arguements, etc.
687 <literal>name</literal> name of mod node.
692 <literal>value</literal> value of mod node.
697 <literal>next</literal>: pointer to next node which is
698 always a mod node (NULL for last entry).
705 <sect3 id="tools.cql.pqf"><title>CQL to PQF conversion</title>
707 Conversion to PQF (and Z39.50 RPN) is tricky by the fact
708 that the resulting RPN depends on the Z39.50 target
709 capabilities (combinations of supported attributes).
710 In addition, the CQL and SRW operates on index prefixes
711 (URI or strings), whereas the RPN uses Object Identifiers
715 The CQL library of &yaz; defines a <literal>cql_transform_t</literal>
716 type. It represents a particular mapping between CQL and RPN.
717 This handle is created and destroyed by the functions:
719 cql_transform_t cql_transform_open_FILE (FILE *f);
720 cql_transform_t cql_transform_open_fname(const char *fname);
721 void cql_transform_close(cql_transform_t ct);
723 The first two functions create a tranformation handle from
724 either an already open FILE or from a filename respectively.
727 The handle is destroyed by <function>cql_transform_close</function>
728 in which case no further reference of the handle is allowed.
731 When a <literal>cql_transform_t</literal> handle has been created
732 you can convert to RPN.
734 int cql_transform_buf(cql_transform_t ct,
735 struct cql_node *cn, char *out, int max);
737 This function converts the CQL tree <literal>cn</literal>
738 using handle <literal>ct</literal>.
739 For the resulting PQF, you supply a buffer <literal>out</literal>
740 which must be able to hold at at least <literal>max</literal>
744 If conversion failed, <function>cql_transform_buf</function>
745 returns a non-zero error code; otherwise zero is returned
746 (conversion successful).
749 If you wish to be able to produce a PQF result in a different
750 way, there are two alternatives.
752 void cql_transform_pr(cql_transform_t ct,
754 void (*pr)(const char *buf, void *client_data),
757 int cql_transform_FILE(cql_transform_t ct,
758 struct cql_node *cn, FILE *f);
760 The former function produces output to a user-defined
761 output stream. The latter writes the result to an already
762 open <literal>FILE</literal>.
765 <sect3 id="tools.cql.map">
766 <title>Specification of CQL to RPN mapping</title>
768 The file supplied to functions
769 <function>cql_transform_open_FILE</function>,
770 <function>cql_transform_open_fname</function> follows
771 a structure found in many Unix utilities.
772 It consists of mapping specifications - one per line.
773 Lines starting with <literal>#</literal> are ignored (comments).
776 Each line is of the form
778 <replaceable>CQL pattern</replaceable><literal> = </literal> <replaceable> RPN equivalent</replaceable>
782 An RPN pattern is a simple attribute list. Each attribute pair
785 [<replaceable>set</replaceable>] <replaceable>type</replaceable><literal>=</literal><replaceable>value</replaceable>
787 The attribute <replaceable>set</replaceable> is optional.
788 The <replaceable>type</replaceable> is the attribute type,
789 <replaceable>value</replaceable> the attribute value.
792 The following CQL patterns are recognized:
795 <literal>qualifier.</literal><replaceable>set</replaceable><literal>.</literal><replaceable>name</replaceable>
799 This pattern is invoked when a CQL qualifier, such as
800 dc.title is converted. <replaceable>set</replaceable>
801 and <replaceable>name</replaceable> is the index set and qualifier
803 Typically, the RPN specifies an equivalent use attribute.
806 For terms not bound by a qualifier the pattern
807 <literal>qualifier.srw.serverChoice</literal> is used.
808 Here, the prefix <literal>srw</literal> is defined as
809 <literal>http://www.loc.gov/zing/cql/srw-indexes/v1.0/</literal>.
810 If this pattern is not defined, the mapping will fail.
815 <literal>relation.</literal><replaceable>relation</replaceable>
819 This pattern specifies how a CQL relation is mapped to RPN.
820 <replaceable>pattern</replaceable> is name of relation
821 operator. Since <literal>=</literal> is used as
822 separator between CQL pattern and RPN, CQL relations
823 including <literal>=</literal> cannot be
824 used directly. To avoid a conflict, the names
825 <literal>ge</literal>,
826 <literal>eq</literal>,
827 <literal>le</literal>,
828 must be used for CQL operators, greater-than-or-equal,
829 equal, less-than-or-equal respectively.
830 The RPN pattern is supposed to include a relation attribute.
833 For terms not bound by a relation, the pattern
834 <literal>relation.scr</literal> is used. If the pattern
835 is not defined, the mapping will fail.
838 The special pattern, <literal>relation.*</literal> is used
839 when no other relation pattern is matched.
845 <literal>relationModifier.</literal><replaceable>mod</replaceable>
849 This pattern specifies how a CQL relation modifier is mapped to RPN.
850 The RPN pattern is usually a relation attribute.
856 <literal>structure.</literal><replaceable>type</replaceable>
860 This pattern specifies how a CQL structure is mapped to RPN.
861 Note that this CQL pattern is somewhat to similar to
862 CQL pattern <literal>relation</literal>.
863 The <replaceable>type</replaceable> is a CQL relation.
866 The pattern, <literal>structure.*</literal> is used
867 when no other structure pattern is matched.
868 Usually, the RPN equivalent specifies a structure attribute.
874 <literal>position.</literal><replaceable>type</replaceable>
878 This pattern specifies how the anchor (position) of
879 CQL is mapped to RPN.
880 The <replaceable>type</replaceable> is one
881 of <literal>first</literal>, <literal>any</literal>,
882 <literal>last</literal>, <literal>firstAndLast</literal>.
885 The pattern, <literal>position.*</literal> is used
886 when no other position pattern is matched.
892 <literal>set.</literal><replaceable>prefix</replaceable>
896 This specification defines a CQL index set for a given prefix.
897 The value on the right hand side is the URI for the set -
898 <emphasis>not</emphasis> RPN. All prefixes used in
899 qualifier patterns must be defined this way.
905 <example><title>Small CQL to RPN mapping file</title>
907 This small file defines two index sets, three qualifiers and three
908 relations, a position pattern and a default structure.
911 set.srw = http://www.loc.gov/zing/cql/srw-indexes/v1.0/
912 set.dc = http://www.loc.gov/zing/cql/dc-indexes/v1.0/
914 qualifier.srw.serverChoice = 1=1016
915 qualifier.dc.title = 1=4
916 qualifier.dc.subject = 1=21
922 position.any = 3=3 6=1
928 <sect3 id="tools.cql.xcql"><title>CQL to XCQL conversion</title>
930 Conversion from CQL to XCQL is trivial and does not
931 require a mapping to be defined.
932 There three functions to choose from depending on the
933 way you wish to store the resulting output (XML buffer
936 int cql_to_xml_buf(struct cql_node *cn, char *out, int max);
937 void cql_to_xml(struct cql_node *cn,
938 void (*pr)(const char *buf, void *client_data),
940 void cql_to_xml_stdio(struct cql_node *cn, FILE *f);
942 Function <function>cql_to_xml_buf</function> converts
943 to XCQL and stores result in a user supplied buffer of a given
947 <function>cql_to_xml</function> writes the result in
948 a user defined output stream.
949 <function>cql_to_xml_stdio</function> writes to a
955 <sect1 id="tools.oid"><title>Object Identifiers</title>
958 The basic YAZ representation of an OID is an array of integers,
959 terminated with the value -1. The &odr; module provides two
960 utility-functions to create and copy this type of data elements:
964 Odr_oid *odr_getoidbystr(ODR o, char *str);
968 Creates an OID based on a string-based representation using dots (.)
969 to separate elements in the OID.
973 Odr_oid *odr_oiddup(ODR odr, Odr_oid *o);
977 Creates a copy of the OID referenced by the <emphasis>o</emphasis>
979 Both functions take an &odr; stream as parameter. This stream is used to
980 allocate memory for the data elements, which is released on a
981 subsequent call to <function>odr_reset()</function> on that stream.
985 The OID module provides a higher-level representation of the
986 family of object identifiers which describe the Z39.50 protocol and its
987 related objects. The definition of the module interface is given in
988 the <filename>oid.h</filename> file.
992 The interface is mainly based on the <literal>oident</literal> structure.
993 The definition of this structure looks like this:
997 typedef struct oident
1002 int oidsuffix[OID_SIZE];
1008 The proto field takes one of the values
1017 If you don't care about talking to SR-based implementations (few
1018 exist, and they may become fewer still if and when the ISO SR and ANSI
1019 Z39.50 documents are merged into a single standard), you can ignore
1020 this field on incoming packages, and always set it to PROTO_Z3950
1021 for outgoing packages.
1025 The oclass field takes one of the values
1047 corresponding to the OID classes defined by the Z39.50 standard.
1049 Finally, the value field takes one of the values
1107 again, corresponding to the specific OIDs defined by the standard.
1111 The desc field contains a brief, mnemonic name for the OID in question.
1119 struct oident *oid_getentbyoid(int *o);
1123 takes as argument an OID, and returns a pointer to a static area
1124 containing an <literal>oident</literal> structure. You typically use
1125 this function when you receive a PDU containing an OID, and you wish
1126 to branch out depending on the specific OID value.
1134 int *oid_ent_to_oid(struct oident *ent, int *dst);
1138 Takes as argument an <literal>oident</literal> structure - in which
1139 the <literal>proto</literal>, <literal>oclass</literal>/, and
1140 <literal>value</literal> fields are assumed to be set correctly -
1141 and returns a pointer to a the buffer as given by <literal>dst</literal>
1143 representation of the corresponding OID. The function returns
1144 NULL and the array dst is unchanged if a mapping couldn't place.
1145 The array <literal>dst</literal> should be at least of size
1146 <literal>OID_SIZE</literal>.
1150 The <function>oid_ent_to_oid()</function> function can be used whenever
1151 you need to prepare a PDU containing one or more OIDs. The separation of
1152 the <literal>protocol</literal> element from the remainder of the
1153 OID-description makes it simple to write applications that can
1154 communicate with either Z39.50 or OSI SR-based applications.
1162 oid_value oid_getvalbyname(const char *name);
1166 takes as argument a mnemonic OID name, and returns the
1167 <literal>/value</literal> field of the first entry in the database that
1168 contains the given name in its <literal>desc</literal> field.
1172 Finally, the module provides the following utility functions, whose
1173 meaning should be obvious:
1177 void oid_oidcpy(int *t, int *s);
1178 void oid_oidcat(int *t, int *s);
1179 int oid_oidcmp(int *o1, int *o2);
1180 int oid_oidlen(int *o);
1185 The OID module has been criticized - and perhaps rightly so
1186 - for needlessly abstracting the
1187 representation of OIDs. Other toolkits use a simple
1188 string-representation of OIDs with good results. In practice, we have
1189 found the interface comfortable and quick to work with, and it is a
1190 simple matter (for what it's worth) to create applications compatible
1191 with both ISO SR and Z39.50. Finally, the use of the
1192 <literal>/oident</literal> database is by no means mandatory.
1193 You can easily create your own system for representing OIDs, as long
1194 as it is compatible with the low-level integer-array representation
1201 <sect1 id="tools.nmem"><title>Nibble Memory</title>
1204 Sometimes when you need to allocate and construct a large,
1205 interconnected complex of structures, it can be a bit of a pain to
1206 release the associated memory again. For the structures describing the
1207 Z39.50 PDUs and related structures, it is convenient to use the
1208 memory-management system of the &odr; subsystem (see
1209 <link linkend="odr-use">Using ODR</link>). However, in some circumstances
1210 where you might otherwise benefit from using a simple nibble memory
1211 management system, it may be impractical to use
1212 <function>odr_malloc()</function> and <function>odr_reset()</function>.
1213 For this purpose, the memory manager which also supports the &odr;
1214 streams is made available in the NMEM module. The external interface
1215 to this module is given in the <filename>nmem.h</filename> file.
1219 The following prototypes are given:
1223 NMEM nmem_create(void);
1224 void nmem_destroy(NMEM n);
1225 void *nmem_malloc(NMEM n, int size);
1226 void nmem_reset(NMEM n);
1227 int nmem_total(NMEM n);
1228 void nmem_init(void);
1229 void nmem_exit(void);
1233 The <function>nmem_create()</function> function returns a pointer to a
1234 memory control handle, which can be released again by
1235 <function>nmem_destroy()</function> when no longer needed.
1236 The function <function>nmem_malloc()</function> allocates a block of
1237 memory of the requested size. A call to <function>nmem_reset()</function>
1238 or <function>nmem_destroy()</function> will release all memory allocated
1239 on the handle since it was created (or since the last call to
1240 <function>nmem_reset()</function>. The function
1241 <function>nmem_total()</function> returns the number of bytes currently
1242 allocated on the handle.
1246 The nibble memory pool is shared amongst threads. POSIX
1247 mutex'es and WIN32 Critical sections are introduced to keep the
1248 module thread safe. Function <function>nmem_init()</function>
1249 initializes the nibble memory library and it is called automatically
1250 the first time the <literal>YAZ.DLL</literal> is loaded. &yaz; uses
1251 function <function>DllMain</function> to achieve this. You should
1252 <emphasis>not</emphasis> call <function>nmem_init</function> or
1253 <function>nmem_exit</function> unless you're absolute sure what
1254 you're doing. Note that in previous &yaz; versions you'd have to call
1255 <function>nmem_init</function> yourself.
1261 <!-- Keep this comment at the end of the file
1266 sgml-minimize-attributes:nil
1267 sgml-always-quote-attributes:t
1270 sgml-parent-document: "yaz.xml"
1271 sgml-local-catalogs: nil
1272 sgml-namecase-general:t