2.1.783 Part 4 Section 188.8.131.52, fieldGroup (Field Group Properties)
a. The standard allows fieldGroup to include both rangePr and discretePr in a valid document.
Office does not allow fieldGroup to include rangePr and discretePr at the same time.
b. The standard does not require the groupItems collection to exist in any circumstances.
In Office, if fieldGroup contains rangePr or discretePr, the groupItems collection must exist and must not be empty.
c. The standard does not provide restrictions on the base attribute.
Office requires that value of the base attribute to be less than number of cacheFields and the cacheField element pointed to by the base value must have a databaseField attribute equal to 1.
d. The standard does not provide restrictions on the par attribute.
Office requires that if fieldGroup has rangePr child, then cacheField pointed to by @par shall have fieldGroup that contains rangePr; the value of the base attribute in that fieldGroup must equal the value of the base attribute on this element.
e. The standard does not specify a dependency between the value of the rangePr element attribute groupBy and the par attribute value.
In Office, if the groupBy attribute of a rangePr child is range, then the par attribute shall not be specified; otherwise, it shall be less than count of cacheFields elements.