14. The machine-readable storage medium of claim 13 , wherein the first XML query language is an XQuery query language.
13. A machine-readable storage medium storing instructions which, when executed by one or more processors, causes: receiving a first query that conforms to a first XML query language; determining that an operator included in the first query requires one or more node references, to one or more nodes, as operands of the operator instead of a value of any of the one or more nodes; wherein the operator included in the first query is one of a node comparison operator or an operator that requires context node traversal; and in response to determining that the operator included in the first query requires one or more node references as operands of the operator, generating, based on the first query, a second query (a) that conforms to a second XML query language that is different than the first XML query language and (b) that includes a particular operator not included in the first query; wherein execution of the particular operator included in the second query causes a reference, to a node in an XML document, to be returned instead of a value of the node.