S8.1.3-1 should be a Producer clause

(S8.1.3-1) This should be a Conformant Interoperable Producer conformance clause. I think this is all you need for 8.1.3, except I would reword it as follows:
"table:formula attribute values shall begin with a namespace prefix and a following ":" character. The namespace prefix shall be Namespace Valid [xml-names] and the namespace shall be one for which the syntax and semantics of the formula following the prefixed ":" is specified."