XMI12 — Problems with section on Linking

The section on Linking (3.8 in the XMI 1.2 RTF draft) has a number of
problems. In general, it doesn't explain the alternative link methods
clearly or give examples for all of them. It also seems to be offering
lots of alternatives where there is no obvious need to do this. Some of
the XLink/XPointer formats (e.g. "|descendant(...)" are now apparently
obsolete. Finally, much of the text of 3.8.2.x is ungrammatical and/or
generally hard to read.