21. The one or more computer readable storage media of claim 12 , wherein compiling the path expression further comprises generating a compiled representation of a path expression step from the path expression, and wherein the compiled representation is different than the path expression step.
21. The one or more computer readable storage media of claim 12 , wherein compiling the path expression further comprises generating a compiled representation of a path expression step from the path expression, and wherein the compiled representation is different than the path expression step. 23. The one or more computer readable storage media of claim 21 , wherein the path expression step indicates that it is to be matched to an element of a particular name, and wherein the compiled representation of the path expression step does not include information indicating any name.