2 requested fixes in DTDs

[Robert D Anderson <robander@us.ibm.com>]

Erik Hennum sent me notifications about the following two items that should
be changed in the classification domain. These came up while Eric Sirois
was doing additional Schema testing.

1. Eric noticed that the current definition of subjectCell violates the
Unique Particle Attribution laws of XML Schema. Specifically, it allows
topicsubject twice, initially as a direct child, and again because it is a
domain substitution element for topicref. The fix for this is to remove
topicsubject as a direct child. This fix does not impact any existing
documents, and the same content model is possible, it just makes it legal.

Testing of this led to the second discovery:

2. The <topicapply> element is a specialization of topicref. It is
currently only available inside <subjectCell>, but was intended to be a
domain substitution for topicref itself. The example in the lang spec
actually shows it this way. Erik commented that the element is mostly
useless unless defined as originally intended, but if the TC is unwilling
to make the change at this point, we will have to fix it in 1.3. The change
will not invalidate any existing Classification maps; it will provide the
topicapply element as an alternative to the topicsubject element everywhere
that the topicsubject element can appear (as originally intended).

The first item is a bug fix, and must be updated. The second item is less
clear. Are there any objections to making this change?

Thanks -

Robert D Anderson
IBM Authoring Tools Development
Chief Architect, DITA Open Toolkit