The "How to edit the Guidelines" document (TCW20) has this in its section "Organization of the Guidelines chapters":
a <specGrp> for the whole module is given at the end of the chapter: it includes the other specifications either directly (by means of an entity reference) or indirectly (by means of a <specGrpRef> pointing to a preceding <specGrp> ).
One aspect of this -- the mention of entity references -- is now obsolete, and I'll change it to refer to the XIncludes we currently use. In addition, though, the AI chapter violates the pattern described here; its
<specGrpRef>s are included not in a
<specGrp> but in its
<moduleSpec>. Rather than changing this directly, I'm raising a ticket in case anyone can remember how or why that came about; there might be some special circumstances I'm not aware of.