Table of Contents
In support of the service API - primarily the ASN module, which provides the programmatic interface to the Z39.50 APDUs, YAZ contains a collection of tools that support the development of applications.
    Since the type-1 (RPN) query structure has no direct, useful string
    representation, every origin application needs to provide some form of
    mapping from a local query notation or representation to a
    Z_RPNQuery structure. Some programmers will prefer to
    construct the query manually, perhaps using
    odr_malloc() to simplify memory management.
    The YAZ distribution includes three separate, query-generating tools
    that may be of use to you.
   
Since RPN or reverse polish notation is really just a fancy way of describing a suffix notation format (operator follows operands), it would seem that the confusion is total when we now introduce a prefix notation for RPN. The reason is one of simple laziness - it's somewhat simpler to interpret a prefix format, and this utility was designed for maximum simplicity, to provide a baseline representation for use in simple test applications and scripting environments (like Tcl). The demonstration client included with YAZ uses the PQF.
The PQF has been adopted by other parties developing Z39.50 software. It is often referred to as Prefix Query Notation - PQN.
The PQF is defined by the pquery module in the YAZ library. There are two sets of functions that have similar behavior. First set operates on a PQF parser handle, second set doesn't. First set of functions are more flexible than the second set. Second set is obsolete and is only provided to ensure backwards compatibility.
First set of functions all operate on a PQF parser handle:
     #include <yaz/pquery.h>
     YAZ_PQF_Parser yaz_pqf_create(void);
     void yaz_pqf_destroy(YAZ_PQF_Parser p);
     Z_RPNQuery *yaz_pqf_parse(YAZ_PQF_Parser p, ODR o, const char *qbuf);
     Z_AttributesPlusTerm *yaz_pqf_scan(YAZ_PQF_Parser p, ODR o,
                          Odr_oid **attributeSetId, const char *qbuf);
     int yaz_pqf_error(YAZ_PQF_Parser p, const char **msg, size_t *off);
    
     A PQF parser is created and destructed by functions
     yaz_pqf_create and
     yaz_pqf_destroy respectively.
     Function yaz_pqf_parse parses the query given
     by string qbuf. If parsing was successful,
     a Z39.50 RPN Query is returned which is created using ODR stream
     o. If parsing failed, a NULL pointer is
     returned.
     Function yaz_pqf_scan takes a scan query in
     qbuf. If parsing was successful, the function
     returns attributes plus term pointer and modifies
     attributeSetId to hold attribute set for the
     scan request - both allocated using ODR stream o.
     If parsing failed, yaz_pqf_scan returns a NULL pointer.
     Error information for bad queries can be obtained by a call to
     yaz_pqf_error which returns an error code and
     modifies *msg to point to an error description,
     and modifies *off to the offset within the last
     query where parsing failed.
    
The second set of functions are declared as follows:
     #include <yaz/pquery.h>
     Z_RPNQuery *p_query_rpn(ODR o, oid_proto proto, const char *qbuf);
     Z_AttributesPlusTerm *p_query_scan(ODR o, oid_proto proto,
                             Odr_oid **attributeSetP, const char *qbuf);
     int p_query_attset(const char *arg);
    
     The function p_query_rpn() takes as arguments an
     ODR stream (see section The ODR Module)
     to provide a memory source (the structure created is released on
     the next call to odr_reset() on the stream), a
     protocol identifier (one of the constants PROTO_Z3950 and
     PROTO_SR), an attribute set reference, and
     finally a null-terminated string holding the query string.
    
     If the parse went well, p_query_rpn() returns a
     pointer to a Z_RPNQuery structure which can be
     placed directly into a Z_SearchRequest.
     If parsing failed, due to syntax error, a NULL pointer is returned.
    
     The p_query_attset specifies which attribute set
     to use if the query doesn't specify one by the
     @attrset operator.
     The p_query_attset returns 0 if the argument is a
     valid attribute set specifier; otherwise the function returns -1.
    
The grammar of the PQF is as follows:
     query ::= top-set query-struct.
     top-set ::= [ '@attrset' string ]
     query-struct ::= attr-spec | simple | complex | '@term' term-type query
     attr-spec ::= '@attr' [ string ] string query-struct
     complex ::= operator query-struct query-struct.
     operator ::= '@and' | '@or' | '@not' | '@prox' proximity.
     simple ::= result-set | term.
     result-set ::= '@set' string.
     term ::= string.
     proximity ::= exclusion distance ordered relation which-code unit-code.
     exclusion ::= '1' | '0' | 'void'.
     distance ::= integer.
     ordered ::= '1' | '0'.
     relation ::= integer.
     which-code ::= 'known' | 'private' | integer.
     unit-code ::= integer.
     term-type ::= 'general' | 'numeric' | 'string' | 'oid' | 'datetime' | 'null'.
    
You will note that the syntax above is a fairly faithful representation of RPN, except for the Attribute, which has been moved a step away from the term, allowing you to associate one or more attributes with an entire query structure. The parser will automatically apply the given attributes to each term as required.
     The @attr operator is followed by an attribute specification
     (attr-spec above). The specification consists
     of an optional attribute set, an attribute type-value pair and
     a sub-query. The attribute type-value pair is packed in one string:
     an attribute type, an equals sign, and an attribute value, like this:
     @attr 1=1003.
     The type is always an integer, but the value may be either an
     integer or a string (if it doesn't start with a digit character).
     A string attribute-value is encoded as a Type-1 "complex"
     attribute with the list of values containing the single string
     specified, and including no semantic indicators.
    
     Version 3 of the Z39.50 specification defines various encoding of terms.
     Use @term  type
     string,
     where type is one of: general,
     numeric or string
     (for InternationalString).
     If no term type has been given, the general form
     is used.  This is the only encoding allowed in both versions 2 and 3
     of the Z39.50 standard.
    
This is an advanced topic, describing how to construct queries that make very specific requirements on the relative location of their operands. You may wish to skip this section and go straight to the example PQF queries.
Most Z39.50 servers do not support proximity searching, or support only a small subset of the full functionality that can be expressed using the PQF proximity operator. Be aware that the ability to express a query in PQF is no guarantee that any given server will be able to execute it.
      The proximity operator @prox is a special
      and more restrictive version of the conjunction operator
      @and.  Its semantics are described in
      section 3.7.2 (Proximity) of Z39.50 the standard itself, which
      can be read on-line at
      https://www.loc.gov/z3950/agency/markup/09.html#3.7.2
     
In PQF, the proximity operation is represented by a sequence of the form
       @prox exclusion distance ordered relation which-code unit-code
      in which the meanings of the parameters are as described in the standard, and they can take the following values:
exclusion. 0 = false (i.e. the proximity condition specified by the remaining parameters must be satisfied) or 1 = true (the proximity condition specified by the remaining parameters must not be satisfied).
distance. An integer specifying the difference between the locations of the operands: e.g. two adjacent words would have distance=1 since their locations differ by one unit.
ordered. 1 = ordered (the operands must occur in the order the query specifies them) or 0 = unordered (they may appear in either order).
relation. Recognised values are 1 (lessThan), 2 (lessThanOrEqual), 3 (equal), 4 (greaterThanOrEqual), 5 (greaterThan) and 6 (notEqual).
which-code. 
	known
	or
	k
	(the unit-code parameter is taken from the well-known list
	of alternatives described below) or
	private
	or
	p
	(the unit-code parameter has semantics specific to an
	out-of-band agreement such as a profile).
       
unit-code. 
	If the which-code parameter is known
	then the recognised values are
	1 (character),
	2 (word),
	3 (sentence),
	4 (paragraph),
	5 (section),
	6 (chapter),
	7 (document),
	8 (element),
	9 (subelement),
	10 (elementType) and
	11 (byte).
	If which-code is private then the
	acceptable values are determined by the profile.
       
(The numeric values of the relation and well-known unit-code parameters are taken straight from the ASN.1 of the proximity structure in the standard.)
Example 7.2. PQF boolean operators
	@or "dylan" "zimmerman"
	@and @or dylan zimmerman when
	@and when @or dylan zimmerman
       
Example 7.4. Attributes for terms
	@attr 1=4 computer
	@attr 1=4 @attr 4=1 "self portrait"
	@attrset exp1 @attr 1=1 CategoryList
	@attr gils 1=2008 Copenhagen
	@attr 1=/book/title computer
       
Example 7.5. PQF Proximity queries
	@prox 0 3 1 2 k 2 dylan zimmerman
       Here the parameters 0, 3, 1, 2, k and 2 represent exclusion, distance, ordered, relation, which-code and unit-code, in that order. So:
exclusion = 0: the proximity condition must hold
distance = 3: the terms must be three units apart
ordered = 1: they must occur in the order they are specified
relation = 2: lessThanOrEqual (to the distance of 3 units)
which-code is "known", so the standard unit-codes are used
unit-code = 2: word.
       So the whole proximity query means that the words
       dylan and zimmerman must
       both occur in the record, in that order, differing in position
       by three or fewer words (i.e. with two or fewer words between
       them.)  The query would find "Bob Dylan, aka. Robert
       Zimmerman", but not "Bob Dylan, born as Robert Zimmerman"
       since the distance in this case is four.
      
Example 7.7. PQF mixed queries
	@or @and bob dylan @set Result-1
	@attr 4=1 @and @attr 1=1 "bob dylan" @attr 1=4 "slow train coming"
	@and @attr 2=4 @attr gils 1=2038 -114 @attr 2=2 @attr gils 1=2039 -109
       The last of these examples is a spatial search: in the GILS attribute set, access point 2038 indicates West Bounding Coordinate and 2030 indicates East Bounding Coordinate, so the query is for areas extending from -114 degrees longitude to no more than -109 degrees longitude.
Not all users enjoy typing in prefix query structures and numerical attribute values, even in a minimalistic test client. In the library world, the more intuitive Common Command Language - CCL (ISO 8777) has enjoyed some popularity - especially before the widespread availability of graphical interfaces. It is still useful in applications where you for some reason or other need to provide a symbolic language for expressing boolean query structures.
      The CCL parser obeys the following grammar for the FIND argument.
      The syntax is annotated using lines prefixed by
      --.
     
      CCL-Find ::= CCL-Find Op Elements
                | Elements.
      Op ::= "and" | "or" | "not"
      -- The above means that Elements are separated by boolean operators.
      Elements ::= '(' CCL-Find ')'
                | Set
                | Terms
                | Qualifiers Relation Terms
                | Qualifiers Relation '(' CCL-Find ')'
                | Qualifiers '=' string '-' string
      -- Elements is either a recursive definition, a result set reference, a
      -- list of terms, qualifiers followed by terms, qualifiers followed
      -- by a recursive definition or qualifiers in a range (lower - upper).
      Set ::= 'set' = string
      -- Reference to a result set
      Terms ::= Terms Prox Term
             | Term
      -- Proximity of terms.
      Term ::= Term string
            | string
      -- This basically means that a term may include a blank
      Qualifiers ::= Qualifiers ',' string
                  | string
      -- Qualifiers is a list of strings separated by comma
      Relation ::= '=' | '>=' | '<=' | '<>' | '>' | '<'
      -- Relational operators. This really doesn't follow the ISO8777
      -- standard.
      Prox ::= '%' | '!'
      -- Proximity operator
     Example 7.8. CCL queries
The following queries are all valid:
       dylan
       "bob dylan"
       dylan or zimmerman
       set=1
       (dylan and bob) or set=1
       righttrunc?
       "notrunc?"
       singlechar#mask
      
       Assuming that the qualifiers ti
       and au
       and date are defined, we may use:
      
       ti=self portrait
       au=(bob dylan and slow train coming)
       date>1980 and (ti=((self portrait)))
      Qualifiers are used to direct the search to a particular searchable index, such as title (ti) and author indexes (au). The CCL standard itself doesn't specify a particular set of qualifiers, but it does suggest a few short-hand notations. You can customize the CCL parser to support a particular set of qualifiers to reflect the current target profile. Traditionally, a qualifier would map to a particular use-attribute within the BIB-1 attribute set. It is also possible to set other attributes, such as the structure attribute.
      A  CCL profile is a set of predefined CCL qualifiers that may be
      read from a file or set in the CCL API.
      The YAZ client reads its CCL qualifiers from a file named
      default.bib. There are four types of
      lines in a CCL profile: qualifier specification,
      qualifier alias, comments and directives.
     
A qualifier specification is of the form:
       qualifier-name
       [attributeset,]type=val
       [attributeset,]type=val ...
      
       where qualifier-name is the name of the
       qualifier to be used (e.g. ti),
       type is attribute type in the attribute
       set (Bib-1 is used if no attribute set is given) and
       val is attribute value.
       The type can be specified as an
       integer, or as a single-letter:
       u for use,
       r for relation, p for position,
       s for structure,t for truncation,
       or c for completeness.
       The attributes for the special qualifier name term
       are used when no CCL qualifier is given in a query.
       
Table 7.1. Common Bib-1 attributes
| Type | Description | 
|---|---|
| u=value | Use attribute (1). Common use attributes are 1 Personal-name, 4 Title, 7 ISBN, 8 ISSN, 30 Date, 62 Subject, 1003 Author, 1016 Any. Specify value as an integer. | 
| r=value | Relation attribute (2). Common values are 1 <, 2 <=, 3 =, 4 >=, 5 >, 6 <>, 100 phonetic, 101 stem, 102 relevance, 103 always matches. | 
| p=value | Position attribute (3). Values: 1 first in field, 2 first in any subfield, 3 any position in field. | 
| s=value | Structure attribute (4). Values: 1 phrase, 2 word, 3 key, 4 year, 5 date, 6 word list, 100 date (un), 101 name (norm), 102 name (un), 103 structure, 104 urx, 105 free-form-text, 106 document-text, 107 local-number, 108 string, 109 numeric string. | 
| t=value | Truncation attribute (5). Values: 1 right, 2 left, 3 left and right, 100 none, 101 process #, 102 regular-1, 103 regular-2, 104 CCL. | 
| c=value | Completeness attribute (6). Values: 1 incomplete subfield, 2 complete subfield, 3 complete field. | 
      
Refer to Bib-1 Attribute Set(7) or the complete list of Bib-1 attributes
It is also possible to specify non-numeric attribute values, which are used in combination with certain types. The special combinations are:
Table 7.2. Special attribute combos
| Name | Description | 
|---|---|
| s=pw | The structure is set to either word or phrase depending on the number of tokens in a term (phrase-word). | 
| s=al | Each token in the term is ANDed (and-list). This does not set the structure at all. | 
| s=ol | Each token in the term is ORed (or-list). This does not set the structure at all. | 
| s=ag | Tokens that appears as phrases (with blank in them) gets structure phrase attached (4=1). Tokens that appear to be words gets structure word attached (4=2). Phrases and words are ANDed. This is a variant of s=al and s=pw, with the main difference that words are not split (with operator AND) but instead kept in one RPN token. This facility appeared in YAZ 4.2.38. | 
| s=sl | Tokens are split into sub-phrases of all combinations - in order. This facility appeared in YAZ 5.14.0. | 
| r=o | Allows ranges and the operators greater-than, less-than, ...
	   equals.
	   This sets Bib-1 relation attribute accordingly (relation
	   ordered). A query construct is only treated as a range if
	   dash is used and that is surrounded by white-space. So -1980is treated as term"-1980"not<= 1980.
	   If- 1980is used, however, that is
	   treated as a range. | 
| r=r | Similar to r=obut assumes that terms
	   are non-negative (not prefixed with-).
	   Thus, a dash will always be treated as a range.
	   The construct1980-1990is
	   treated as a range withr=rbut as a
	   single term"1980-1990"withr=o. The special attributer=ris available in YAZ 2.0.24 or later. | 
| r=omiteq | This will omit relation=equals (@attr 2=3) when r=o / r=r is used. This is useful for servers that somehow break when an explicit relation=equals is used. Omitting the relation is usually safe because "equals" is the default behavior. This tweak was added in YAZ version 5.1.2. | 
| t=l | Allows term to be left-truncated.
	   If term is of the form ?x, the resulting
	   Type-1 term isxand truncation is left. | 
| t=r | Allows term to be right-truncated.
	   If term is of the form x?, the resulting
	   Type-1 term isxand truncation is right. | 
| t=n | If term is does not include ?, the
	   truncation attribute is set to none (100). | 
| t=b | Allows term to be both left-and-right truncated.
	   If term is of the form ?x?, the
	   resulting term isxand truncation is
	   set to both left and right. | 
| t=x | Allows masking anywhere in a term, thus fully supporting # (mask one character) and ? (zero or more of any). If masking is used, truncation is set to 102 (regexp-1 in term) and the term is converted accordingly to a regular expression. | 
| t=z | Allows masking anywhere in a term, thus fully supporting # (mask one character) and ? (zero or more of any). If masking is used, truncation is set to 104 (Z39.58 in term) and the term is converted accordingly to Z39.58 masking term - actually the same truncation as CCL itself. | 
      
Example 7.9. CCL profile
Consider the following definition:
	ti       u=4 s=1
	au       u=1 s=1
	term     s=105
	ranked   r=102
	date     u=30 r=o
       
	ti and au both set
	structure attribute to phrase (s=1).
	ti
	sets the use-attribute to 4. au sets the
	use-attribute to 1.
	When no qualifiers are used in the query, the structure-attribute is
	set to free-form-text (105) (rule for term).
	The date sets the relation attribute to
	the relation used in the CCL query and sets the use attribute
	to 30 (Bib-1 Date).
       
You can combine attributes. To Search for "ranked title" you can do
ti,ranked=knuth computer
which will set relation=ranked, use=title, structure=phrase.
Query
date > 1980
is a valid query. But
ti > 1980
is invalid.
A qualifier alias is of the form:
       q
       q1 q2 ..
      
       which declares q to
       be an alias for q1,
       q2... such that the CCL
       query q=x is equivalent to
       q1=x or q2=x or ....
      
       Lines with white space or lines that begin with
       character # are treated as comments.
      
Directive specifications takes the form
@directive value
      
Table 7.3. CCL directives
| Name | Description | Default | 
|---|---|---|
| truncation | Truncation character | ? | 
| mask | Masking character. Requires YAZ 4.2.58 or later | # | 
| field | Specifies how multiple fields are to be
	   combined. There are two modes: or:
	   multiple qualifier fields are ORed,merge: attributes for the qualifier
	   fields are merged and assigned to one term. | merge | 
| case | Specifies if CCL operators and qualifiers should be compared with case sensitivity or not. Specify 1 for case sensitive; 0 for case insensitive. | 1 | 
| and | Specifies token for CCL operator AND. | and | 
| or | Specifies token for CCL operator OR. | or | 
| not | Specifies token for CCL operator NOT. | not | 
| set | Specifies token for CCL operator SET. | set | 
      All public definitions can be found in the header file
      ccl.h. A profile identifier is of type
      CCL_bibset. A profile must be created with the call
      to the function ccl_qual_mk which returns a profile
      handle of type CCL_bibset.
     
      To read a file containing qualifier definitions the function
      ccl_qual_file may be convenient. This function
      takes an already opened FILE handle pointer as
      argument along with a CCL_bibset handle.
     
To parse a simple string with a FIND query use the function
struct ccl_rpn_node *ccl_find_str(CCL_bibset bibset, const char *str,
                                  int *error, int *pos);
     
      which takes the CCL profile (bibset) and query
      (str) as input. Upon successful completion the RPN
      tree is returned. If an error occurs, such as a syntax error, the integer
      pointed to by error holds the error code and
      pos holds the offset inside query string in which
      the parsing failed.
     
      An English representation of the error may be obtained by calling
      the ccl_err_msg function. The error codes are
      listed in ccl.h.
     
      To convert the CCL RPN tree (type
      struct ccl_rpn_node *)
      to the Z_RPNQuery of YAZ the function ccl_rpn_query
      must be used. This function which is part of YAZ is implemented in
      yaz-ccl.c.
      After calling this function the CCL RPN tree is probably no longer
      needed. The ccl_rpn_delete destroys the CCL RPN tree.
     
      A CCL profile may be destroyed by calling the
      ccl_qual_rm function.
     
      The token names for the CCL operators may be changed by setting the
      globals (all type char *)
      ccl_token_and, ccl_token_or,
      ccl_token_not and ccl_token_set.
      An operator may have aliases, i.e. there may be more than one name for
      the operator. To do this, separate each alias with a space character.
     
CQL - Common Query Language - was defined for the SRU protocol. In many ways CQL has a similar syntax to CCL. The objective of CQL is different. Where CCL aims to be an end-user language, CQL is the protocol query language for SRU.
If you are new to CQL, read the Gentle Introduction.
The CQL parser in YAZ provides the following:
It parses and validates a CQL query.
It generates a C structure that allows you to convert a CQL query to some other query language, such as SQL.
The parser converts a valid CQL query to PQF, thus providing a way to use CQL for both SRU servers and Z39.50 targets at the same time.
The parser converts CQL to XCQL. XCQL is an XML representation of CQL. XCQL is part of the SRU specification. However, since SRU supports CQL only, we don't expect XCQL to be widely used. Furthermore, CQL has the advantage over XCQL that it is easy to read.
      A CQL parser is represented by the CQL_parser
      handle. Its contents should be considered YAZ internal (private).
      
#include <yaz/cql.h>
typedef struct cql_parser *CQL_parser;
CQL_parser cql_parser_create(void);
void cql_parser_destroy(CQL_parser cp);
      
     A parser is created by cql_parser_create and
     is destroyed by cql_parser_destroy.
     
To parse a CQL query string, the following function is provided:
int cql_parser_string(CQL_parser cp, const char *str);
      
      A CQL query is parsed by the cql_parser_string
      which takes a query str.
      If the query was valid (no syntax errors), then zero is returned;
      otherwise -1 is returned to indicate a syntax error.
     
int cql_parser_stream(CQL_parser cp,
                      int (*getbyte)(void *client_data),
                      void (*ungetbyte)(int b, void *client_data),
                      void *client_data);
int cql_parser_stdio(CQL_parser cp, FILE *f);
      
      The functions cql_parser_stream and
      cql_parser_stdio parse a CQL query
      - just like cql_parser_string.
      The only difference is that the CQL query can be
      fed to the parser in different ways.
      The cql_parser_stream uses a generic
      byte stream as input. The cql_parser_stdio
      uses a FILE handle which is opened for reading.
     
If the query string is valid, the CQL parser generates a tree representing the structure of the CQL query.
struct cql_node *cql_parser_result(CQL_parser cp);
      
      cql_parser_result returns
      a pointer to the root node of the resulting tree.
     
      Each node in a CQL tree is represented by a
      struct cql_node.
      It is defined as follows:
      
#define CQL_NODE_ST 1
#define CQL_NODE_BOOL 2
#define CQL_NODE_SORT 3
struct cql_node {
    int which;
    union {
        struct {
            char *index;
	    char *index_uri;
            char *term;
            char *relation;
	    char *relation_uri;
            struct cql_node *modifiers;
        } st;
        struct {
            char *value;
            struct cql_node *left;
            struct cql_node *right;
            struct cql_node *modifiers;
        } boolean;
        struct {
            char *index;
            struct cql_node *next;
            struct cql_node *modifiers;
            struct cql_node *search;
        } sort;
    } u;
};
      There are three node types: search term (ST), boolean (BOOL) and sortby (SORT). A modifier is treated as a search term too.
The search term node has five members:
         index: index for search term.
         If an index is unspecified for a search term,
         index will be NULL.
        
         index_uri: index URI for search term
	 or NULL if none could be resolved for the index.
        
         term: the search term itself.
        
         relation: relation for search term.
        
         relation_uri: relation URI for search term.
        
         modifiers: relation modifiers for search
         term. The modifiers list itself of cql_nodes
	 each of type ST.
        
      The boolean node represents and,
      or, not +
      proximity.
      
         left and right: left
         - and right operand respectively.
        
         modifiers: proximity arguments.
        
The sort node represents both the SORTBY clause.
Conversion to PQF (and Z39.50 RPN) is tricky by the fact that the resulting RPN depends on the Z39.50 target capabilities (combinations of supported attributes). In addition, the CQL and SRU operates on index prefixes (URI or strings), whereas the RPN uses Object Identifiers for attribute sets.
      The CQL library of YAZ defines a cql_transform_t
      type. It represents a particular mapping between CQL and RPN.
      This handle is created and destroyed by the functions:
     
cql_transform_t cql_transform_open_FILE (FILE *f);
cql_transform_t cql_transform_open_fname(const char *fname);
void cql_transform_close(cql_transform_t ct);
     The first two functions create a transformation handle from either an already open FILE or from a filename respectively.
      The handle is destroyed by cql_transform_close
      in which case no further reference of the handle is allowed.
     
      When a cql_transform_t handle has been created
      you can convert to RPN.
      
int cql_transform_buf(cql_transform_t ct,
                      struct cql_node *cn, char *out, int max);
      
      This function converts the CQL tree cn
      using handle ct.
      For the resulting PQF, you supply a buffer out
      which must be able to hold at at least max
      characters.
     
      If conversion failed, cql_transform_buf
      returns a non-zero SRU error code; otherwise zero is returned
      (conversion successful).  The meanings of the numeric error
      codes are listed in the SRU specification somewhere (no
      direct link anymore).
     
If conversion fails, more information can be obtained by calling
int cql_transform_error(cql_transform_t ct, char **addinfop);
      
      This function returns the most recently returned numeric
      error-code and sets the string-pointer at
      *addinfop to point to a string containing
      additional information about the error that occurred: for
      example, if the error code is 15 ("Illegal or unsupported context
      set"), the additional information is the name of the requested
      context set that was not recognised.
     
The SRU error-codes may be translated into brief human-readable error messages using
const char *cql_strerror(int code);
      
If you wish to be able to produce a PQF result in a different way, there are two alternatives.
void cql_transform_pr(cql_transform_t ct,
                      struct cql_node *cn,
                      void (*pr)(const char *buf, void *client_data),
                      void *client_data);
int cql_transform_FILE(cql_transform_t ct,
                       struct cql_node *cn, FILE *f);
      
      The former function produces output to a user-defined
      output stream. The latter writes the result to an already
      open FILE.
     
      The file supplied to functions
      cql_transform_open_FILE,
      cql_transform_open_fname follows
      a structure found in many Unix utilities.
      It consists of mapping specifications - one per line.
      Lines starting with # are ignored (comments).
     
Each line is of the form
       CQL pattern =   RPN equivalent
      
An RPN pattern is a simple attribute list. Each attribute pair takes the form:
       [set] type=value
      
      The attribute set is optional.
      The type is the attribute type,
      value the attribute value.
     
      The character * (asterisk) has special meaning
      when used in the RPN pattern.
      Each occurrence of * is substituted with the
      CQL matching name (index, relation, qualifier etc).
      This facility can be used to copy a CQL name verbatim to the RPN result.
     
The following CQL patterns are recognized:
index.set.name
	
          This pattern is invoked when a CQL index, such as
          dc.title is converted. set
          and name are the context set and index
          name respectively.
          Typically, the RPN specifies an equivalent use attribute.
         
          For terms not bound by an index, the pattern
          index.cql.serverChoice is used.
          Here, the prefix cql is defined as
          http://www.loc.gov/zing/cql/cql-indexes/v1.0/.
          If this pattern is not defined, the mapping will fail.
         
          The pattern,
          index.set.*
          is used when no other index pattern is matched.
	 
qualifier.set.name
	 (DEPRECATED)
        
	  For backwards compatibility, this is recognised as a synonym of
          index.set.name
         
relation.relation
        
          This pattern specifies how a CQL relation is mapped to RPN.
          The pattern is name of relation
          operator. Since = is used as
          separator between CQL pattern and RPN, CQL relations
          including = cannot be
          used directly. To avoid a conflict, the names
          ge,
          eq,
          le,
          must be used for CQL operators, greater-than-or-equal,
          equal, less-than-or-equal respectively.
          The RPN pattern is supposed to include a relation attribute.
         
          For terms not bound by a relation, the pattern
          relation.scr is used. If the pattern
          is not defined, the mapping will fail.
         
          The special pattern, relation.* is used
          when no other relation pattern is matched.
         
relationModifier.mod
        This pattern specifies how a CQL relation modifier is mapped to RPN. The RPN pattern is usually a relation attribute.
structure.type
        
          This pattern specifies how a CQL structure is mapped to RPN.
          Note that this CQL pattern is somewhat similar to
          CQL pattern relation.
          The type is a CQL relation.
         
          The pattern, structure.* is used
          when no other structure pattern is matched.
          Usually, the RPN equivalent specifies a structure attribute.
         
position.type
        
          This pattern specifies how the anchor (position) of
          CQL is mapped to RPN.
          The type is one
          of first, any,
          last, firstAndLast.
         
          The pattern, position.* is used
          when no other position pattern is matched.
         
set.prefix
        This specification defines a CQL context set for a given prefix. The value on the right hand side is the URI for the set - not RPN. All prefixes used in index patterns must be defined this way.
set
	This specification defines a default CQL context set for index names. The value on the right hand side is the URI for the set.
Example 7.10. CQL to RPN mapping file
This simple file defines two context sets, three indexes and three relations, a position pattern and a default structure.
       set.cql  = http://www.loc.gov/zing/cql/context-sets/cql/v1.1/
       set.dc   = http://www.loc.gov/zing/cql/dc-indexes/v1.0/
       index.cql.serverChoice = 1=1016
       index.dc.title         = 1=4
       index.dc.subject       = 1=21
       relation.<             = 2=1
       relation.eq            = 2=3
       relation.scr           = 2=3
       position.any           = 3=3 6=1
       structure.*            = 4=1
      With the mappings above, the CQL query
        computer
       is converted to the PQF:
        @attr 1=1016 @attr 2=3 @attr 4=1 @attr 3=3 @attr 6=1 "computer"
       
       by rules index.cql.serverChoice,
       relation.scr, structure.*,
       position.any.
      
CQL query
        computer^
       
       is rejected, since position.right is
       undefined.
      
CQL query
        >my = "http://www.loc.gov/zing/cql/dc-indexes/v1.0/" my.title = x
       is converted to
        @attr 1=4 @attr 2=3 @attr 4=1 @attr 3=3 @attr 6=1 "x"
       
Example 7.11. CQL to RPN string attributes
In this example we allow any index to be passed to RPN as a use attribute.
       # Identifiers for prefixes used in this file. (index.*)
       set.cql  = info:srw/cql-context-set/1/cql-v1.1
       set.rpn  = http://bogus/rpn
       set      = http://bogus/rpn
       # The default index when none is specified by the query
       index.cql.serverChoice     = 1=any
       index.rpn.*                = 1=*
       relation.eq                = 2=3
       structure.*                = 4=1
       position.any               = 3=3
      
       The http://bogus/rpn context set is also the default
       so we can make queries such as
       
        title = a
       which is converted to
        @attr 2=3 @attr 4=1 @attr 3=3 @attr 1=title "a"
       
Example 7.12. CQL to RPN using Bath Profile
       The file etc/pqf.properties has mappings from
       the Bath Profile and Dublin Core to RPN.
       If YAZ is installed as a package it's usually located
       in /usr/share/yaz/etc and part of the
       development package, such as libyaz-dev.
      
Conversion from CQL to XCQL is trivial and does not require a mapping to be defined. There are three functions to choose from depending on the way you wish to store the resulting output (XML buffer containing XCQL).
int cql_to_xml_buf(struct cql_node *cn, char *out, int max);
void cql_to_xml(struct cql_node *cn,
                void (*pr)(const char *buf, void *client_data),
                void *client_data);
void cql_to_xml_stdio(struct cql_node *cn, FILE *f);
      
      Function cql_to_xml_buf converts
      to XCQL and stores the result in a user-supplied buffer of a given
      max size.
     
      cql_to_xml writes the result in
      a user-defined output stream.
      cql_to_xml_stdio writes to a
      a file.
     
Conversion from PQF to CQL is offered by the two functions shown below. The former uses a generic stream for result. The latter puts result in a WRBUF (string container).
#include <yaz/rpn2cql.h>
int cql_transform_rpn2cql_stream(cql_transform_t ct,
                                 void (*pr)(const char *buf, void *client_data),
                                 void *client_data,
                                 Z_RPNQuery *q);
int cql_transform_rpn2cql_wrbuf(cql_transform_t ct,
                                WRBUF w,
                                Z_RPNQuery *q);
      The configuration is the same as used in CQL to PQF conversions.