11. The computer accessible memory medium of claim 9 , wherein the memory medium stores XML database statistics adapted to be used by the compiler for generating the one or more alternative execution plans.
9. A computer accessible memory medium storing program instructions for executing a extended markup language (XML) database query, wherein the program instructions are executable by a processor implement: a compiler adapted to generate at least two database query execution plans, wherein upon execution the at least two alternate execution plans provide a same response to the XML database query; and at least one switch adapted to select one of the at least two database query execution plans during runtime; and an execution engine adapted to execute the selected execution plan; wherein said selecting comprises the at least one switch dynamically selecting one of the at least two alternative database query execution plans, wherein the switch performs the selection based on intermediate results, which are at least partly reused for evaluating the result of the execution of the XML database query according to at least one of the at least two alternative database query execution plans.