While the DTD supports
writing text to describe something, there doesn't seem
to be any way to
distinguish text that's part of an informal
proposition. Here's an example
of what needs to appear in the document:
IP1 : Some text that restricts something goes here.
It works just like a "Formal proposition" (which is a
where rule), except
it's not written in EXPRESS, only in English. Informal
Formal propositions in the subclause describing and
entity. By the way, the
product identification module does this incorrectly
with something they
invented called an "Attribute value restriction".