2.1.191 Part 1 Section 220.127.116.11, smartTag (Inline-Level Smart Tag)
For additional notes that apply to this portion of the standard, please see the notes for oMath, §18.104.22.168(c) .
a. The standard states that the element attribute can contain any string value.
Word only allows values for this attribute that conform to the xsd:NCName datatype.