QUERY(1)						User Contributed Perl Documentation						  QUERY(1)

NAME

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

SYNOPSIS

	use XML::XQL;

	$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 "Con-
	   stant 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 oth-
       ers:

	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

perl v5.8.0							    2000-01-31								  QUERY(1)