My AI, documentation of conref restrictions

Su-Laine recognized that some of the restrictions that 
concerned her are due to XMetaL being in some respects more strict than the spec 
in its treatment of conref. Nevertheless, in surveying topics about conref, 
keys, etc., it became increasingly clear to me how the nexus of 
interrelated parts that constitutes DITA support for use by 
reference requires an overview in one place, with links to more detailed 
topics on the individual pieces.
 
With some discussion with Kris and with Eliot, my 
approach to this evolved into a rewrite of the "Content reuse" topic 
(conref.dita). Judging from draft comments in that topic, I am wading boldly in 
where angels fear, etc., but I see no effective alternative. However, I did not 
modify the original conref.dita, my rewrite is in a separate file. This is 
anomalously named Use_By_Reference.dita and can be renamed appropriately if the 
decision is made to use it. 
 
Here are the main points of what I have 
done:

  Reorganized it as sections in one concept 
  topic.
  Changed 
  source/target to referencing/referenced.
  Added related-links for access to the more detailed 
  topics.
  Changed the title to "Use by reference" rather than 
  "Content inclusion".
  Included a brief section on <topicref>. 
  
  Included, but on advice from Eliot commented out, 
  discussion of use of <fn> by reference from 
  <xref>.
  Recast some of the text for 
  clarity.
This document needs technical review to make sure I 
haven't munged things, and obviously any of this can be changed, including the 
fundamental strategy.
 
There are two technical questions in the body of the 
topic, written in XML comments, where the language seemed to me unclear or 
incomplete and I couldn't resolve the intended meaning.
 
There is also a question about how to make one of the 
related links, which should probably be dealt with off line with Kris or 
someone. Here it is, and it is also noted in a 
comment written on the last of the related links. This is the link to 
"Common attribute definitions", which is currently rendered in the lang 
ref, but which probably should be rendered in the arch spec. (If I understood 
him correctly, Eliot thought nothing in the common folder should be used in the 
lang ref, but this is a clear counterexample.) I found 
 ../common/complexattributedefinitions.dita but don't yet know enough about 
the organization of the content to see how the content that is rendered below it 
in the lang ref gets assembled. Is a link pointing to that (short) topic 
sufficient?
 
Seeing no information on how to upload a file for 
interested members to access from the wiki, I am attaching it. My apology if 
that's an annoyance to anyone.
 
    
/Bruce