NAME

       XML::XQL::Query - Creates an XQL query evaluater from a XQL expression

SYNOPSIS

        use XML::XQL;
        use XML::XQL::DOM;

        $parser = new XML::DOM::Parser;
        $doc = $parser->parsefile ("file.xml");

        # Return all elements with tagName='title' under the root element 'book'
        $query = new XML::XQL::Query (Expr => "book/title");
        @result = $query->solve ($doc);

        # Or (to save some typing)
        @result = XML::XQL::solve ("book/title", $doc);

DESCRIPTION

       To perform XQL queries on an XML::DOM document (or, in the future, on other XML storage
       structures), you first have to create an XML::XQL::Query object and pass it a valid XQL
       query expression. You can then perform queries on one or more documents by calling the
       solve() method.

XML::XQL::Query constructor

       Usage, e.g:

        $query = new XML::XQL::Query(
               Expr => "book/author",
               Func => [ myfunc => \&my_func,          # define 2 functions
                         myfunc2 => \&my_func2 ],
               FuncArgCount => [ myfunc2 => [2, -1] ], # myfunc2 has 2 or more args
               AllowedOutSideSubquery => [ myfunc => 1 ],
               ConstFunc => [ myfunc2 => 1],
               CompareOper => [ mycmp => \&mycmp ],    # define comparison operator
               q => "str");                            # use str// as string delim

       Expr => STRING
           The query expression to be evaluated.

       NodeQuery => BOOLEAN
           If set to 1, the query is a Node Query as opposed to a Full Query (which is the
           default.)  A node query is a query that is only capable of returning Nodes.  A full
           query is capable of returning Node values and non-Node values.  Non-Node values
           include XML Primitives, element type names, namespace URI's, concatenated text nodes,
           and node type names. The distinction is significant because node queries may appear as
           XSL match and select patterns, while full queries have use in other applications.  The
           difference between the two forms of queries is trivial and exists only as constraints
           on the syntax of node queries.  Node queries may contain nested full queries.

       Func => [ FUNCNAME => FUNCREF, ...]
           Defines one or more functions. FUNCNAME is the name as used in the query expression.
           FUNCREF can be either a function reference like \&my_func or an anonymous sub.  See
           also: defineFunction

       Method => [ FUNCNAME => FUNCREF, ...]
           Defines one or more methods. FUNCNAME is the name as used in the query expression.
           FUNCREF can be either a function reference like \&my_func or an anonymous sub.  See
           also: defineMethod

       FuncArgCount => [ FUNCNAME => ARGCOUNT, ...]
           Defines the number of arguments for one or more functions or methods.  FUNCNAME is the
           name as used in the query expression.  See also: defineFunction and defineMethod

       AllowedOutsideSubquery => [ FUNCNAME => BOOLEAN, ...]
           Defines whether the specified function or method is allowed outside subqueries.
           FUNCNAME is the name as used in the query expression.  See also: defineFunction and
           defineMethod

       ConstFunc => [ FUNCNAME => BOOLEAN, ...]
           Defines whether the function (not method!) is a "constant" function.  FUNCNAME is the
           name as used in the query expression.  See "Constant Function Invocations" for a
           definition of "constant" See also: defineFunction and defineMethod

       CompareOper => [ OPERNAME => FUNCREF, ...]
           Defines the comparison operator with the specified OPERNAME, e.g. if OPERNAME is
           "contains", you can use "$contains$" in the query.  See also:
           defineComparisonOperators

       q => TOKEN
           Defines the q// token. See also: defineTokenQ

       qq => TOKEN
           Defines the qq// token. See also: defineTokenQQ

       Error => FUNCREF
           Defines the function that is called when errors occur during parsing the query
           expression. The default function prints an error message to STDERR.

       Debug => FLAGS
           Sets the debug level for the Yapp parser that parses the query expression.  Default
           value is 0 (don't print anything). The maximum value is 0x17, which prints a lot of
           stuff. See the Parse::Yapp manpage for the meaning of the individual bits.

       Reserved hash keys
           Users may add their own (key, value) pairs to the Query constructor.  Beware that the
           key 'Tree' is used internally.

XML::XQL::Query methods

       solve (INPUT_LIST...)
           Note that solve takes a list of nodes which are assumed to be in document order and
           must belong to the same document. E.g:

            $query = new XML::XQL::Query (Expr => "doc//book");
            @result = $query->solve ($doc);
            @result2 = $query->solve ($node1, $node2, $node3);

       The following functions are also available at the query level, i.e. when called on a Query
       object they only affect this Query and no others:

        defineFunction, defineMethod, defineComparisonOperators,
        defineTokenQ, defineTokenQQ

       See Global functions for details.  Another way to define these features for a particular
       Query is by passing the appropriate values to the XML::XQL::Query constructor.

SEE ALSO

       XML::XQL for general information about the XML::XQL module

       XML::XQL::Tutorial which describes the XQL syntax