minor technical: A.7 grammar, rule [25] Constraint

Appendix A.7 grammar
Rule [25] "Constraint" permits a FILTER to be followed by a BuiltInCall
or FunctionCall.  While this is parsable and might occasionally be
used in queries (see examples in section 11.2.3 "Operators introduced
in SPARQL"), it would be better from a
consistency standpoint to eliminate this possibility, as BuiltInCall
and FunctionCall are varieties of Expression. In that case the rule is
simply that FILTER is always followed by a parenthesized expression.

Fred Zemke