1. A method comprising performing a machine-executed operation involving instructions, wherein the machine-executed operation is at least one of: A) sending said instructions over transmission media; B) receiving said instructions over transmission media; C) storing said instructions onto a machine-readable storage medium; and D) executing the instructions; wherein said instructions are instructions which, when executed by one or more processors, cause the one or more processors to perform the steps of: receiving a query that targets a container that contains a plurality of XML documents, wherein at least two of the XML documents in the container do not conform to the same XML schema; and generating a plurality of execution plans for said query, wherein each execution plan of said plurality of execution plans is associated with a different XML schema; and using each execution plan to execute the query relative to those XML documents, within the container, that conform to the XML schema associated with the execution plan.