XML::XQL::Query(3) User Contributed Perl Documentation XML::XQL::Query(3)NAMEXML::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 capa-
ble of returning Nodes. A full query is capable of returning Node
values and non-Node values. Non-Node values include XML Primi-
tives, 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 con-
straints 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 meth-
ods. 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" func-
tion. 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 pars-
ing the query expression. The default function prints an error mes-
sage 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 construc-
tor. 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 v5.8.8 2000-01-31 XML::XQL::Query(3)
