RE: [dita] Why There are Constraints on Conref

["Tony Self" <tself@hyperwrite.com>]

Thanks for the clarification, Jeff.

With regard to the terms "conref source" and "conref target", I have been
using "conref source" to mean the element containing the content to be
re-used (with an id attribute), and "conref target" to mean the element into
which the content source is included (with a conref attribute). Am I using
the terms the wrong way round?

Cheers

Tony

-----Original Message-----
From: Ogden, Jeff [mailto:jogden@ptc.com] 
Sent: Tuesday, 29 September 2009 11:35 PM
To: tself@hyperwrite.com; dita
Subject: RE: [dita] Why There are Constraints on Conref

Tony,

I think the description in your message is correct.  In another message
Rob said that you had things reversed, but I think the problem is just
some ambiguity in the wording so that it isn't completely clear what is
the conref source and what is the conref target.

In the html file you attached there is an example of how constraints are
declared using @constraints and @constraints-scope, but I think that
approach is obsolete and has been replaced with a declaration that is
part of @domains.

Your html file also says that you can add and remove attributes, but I'm
pretty sure you can only remove attributes using constraints.

And as Rob says, the reason that you can't just test to see if the
conref material is legal based on the DTD or XSD is that test would be
based upon the content in a particular conref target document instance
at a particular time and at a different time the same conref target
document might be different and might be invalid.  The current conref
validation scheme gives you a guarantee that what is a valid conref will
remain valid into the future.  This guarantee comes at the expense of a
more restrictive policy then is absolutely necessary under some
circumstances.  But the restrictive policy is very similar to the policy
that has existed for a long time with respect to conref and domains and
as far as I know that hasn't been a serious problem.

   -Jeff