20. The computer program product of claim 19 , wherein the query includes search criteria relating to content of the structured document and a node identifier of a leaf vNode includes content of the leaf vNode, and wherein identifying the first vNode comprises comparing, for each leaf vNode, the content of a leaf vNode with the search criteria of the query to identify a matching vNode that includes content matching the search criteria of the query.
20. The computer program product of claim 19 , wherein the query includes search criteria relating to content of the structured document and a node identifier of a leaf vNode includes content of the leaf vNode, and wherein identifying the first vNode comprises comparing, for each leaf vNode, the content of a leaf vNode with the search criteria of the query to identify a matching vNode that includes content matching the search criteria of the query. 21. The computer program product of claim 20 , wherein a first argument of the vFunction includes a version identifier, and wherein identifying the first vNode further comprises comparing the version identifier included in the versioning information of the matching vNode to the version identifier of the first argument of the vFunction, and determining that the matching vNode is the first vNode when the version identifier of the matching vNode matches the first argument of the vFunction included in the query.