11. One or more non-transitory computer-readable media storing instructions which, when executed by one or more processors, cause: receiving one or more criteria that identifies particular nodes within one or more XML documents to exclude from query evaluation; based on the one or more criteria, generating a representation of the one or more XML documents that excludes the particular nodes; receiving a query that specifies a path operation based on a path, wherein one or more of said particular nodes are under said path in the one or more XML documents; and using the representation to compute the path operation as if the one or more of said particular nodes is not in the one or more XML documents.
11. One or more non-transitory computer-readable media storing instructions which, when executed by one or more processors, cause: receiving one or more criteria that identifies particular nodes within one or more XML documents to exclude from query evaluation; based on the one or more criteria, generating a representation of the one or more XML documents that excludes the particular nodes; receiving a query that specifies a path operation based on a path, wherein one or more of said particular nodes are under said path in the one or more XML documents; and using the representation to compute the path operation as if the one or more of said particular nodes is not in the one or more XML documents. 16. The one or more non-transitory computer-readable media of claim 11 , wherein the one or more criteria identifies a namespace within the one or more XML documents.