I'm guessing that if I check the "Use Saxon EE (schema aware) for xslt2 query binding - If checked, Saxon EE will be used for xslt2 query binding." box in the "ISO Schematron" section of the XML / XML Parser preferences page, then oXygen will use Saxon EE to validate my documents against an ISO Schematron schema that uses xslt2 query binding. But what does oXygen use as an ISO Schematron validator if I *don't* check that box? (The documentation under the Help menu doesn't say.) As I side note, I'm asking because I'm getting warnings from the validation that I thought might really be indicative of a processor- specific problem, rather than a Schematron schema or validation error. Probatron does not complain, but oXygen warns that "The attribute axis starting at an attribute node will never select anything" and that "The child axis starting at an attribute node will never select anything". The rule that generates the complaint is <rule context="tei:*/@*"> ... </rule> So I'm guessing that the processor tried to convert this to some generic XSLT that included a match pattern that would never fire. So I tried switching processors to Saxon EE, but that just added an error to the warnings: "Cannot validate <TEI>: no element declaration available". It took a Google search to find out that setting oXygen to use Saxon's -vlax switch is how to deal with that. (Found http://www.oxygenxml.com/forum/topic4460.html.)