-----Original Message----- From: Ogden, Jeff [mailto:jog...@ptc.com] Sent: Tuesday, 29 September 2009 11:35 PM To: tse...@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is an example of how constraints are declared using @constraints and @constraints-scope, but I think that approach is obsolete and has been replaced with a declaration that is part of @domains.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