2.1.429 Part 4 Section 188.8.131.52, smartTagType (Supplementary Smart Tag Information)
a. The standard does explicitly state that this element can be ignored under certain conditions.
Word ignores this element if either the name or namespaceuri attribute is omitted, or the attributes do not identify a smart tag contained in the document.
b. The standard does not say that the url attribute can be ignored under certain conditions.
Word ignores this attribute when the application already has URL information for this name/namespaceuri combination.