2.1.802 Part 1 Section 18.10.1.97, x (Shared Items Index)

a.   The standard specifies that the x element is an array of indexes.

Office assumes that the value of x@v is an index into the shared items collection.

b.   The standard does not place a limit on the value of @v.

Office requires that @v shall be less than sharedItems count.

c.   The standard does not specify different restrictions for @v based on the parent element of x.

In Office if the parent is the reference element, then restrictions of this value are defined by reference@field. If the parent is the tables element, then this value specifies the index into the table tag position in @url.