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From: <petsa@us.ibm.com>
Date: Fri, 9 Apr 1999 09:54:28 -0400
To: rbourret@ito.tu-darmstadt.de, www-xml-schema-comments@w3.org
cc: murray@muzmo.com, C M Sperberg-McQueen <cmsmcq@acm.org>, connolly@w3.org
Message-ID: <8525674E.004C5955.00@D51MTA03.pok.ibm.com>
Ron:
This is in reply to your comments on the XML Schema requirements document
sent on February 26.  I apologize for not getting back to you earlier.  This is
not
sufficient excuse but we have been busy with design work and, you will be happy
to know, it is going well.

You raised the following specific points in your note.
1. Clarify relationship between schemas and DTDs.
The requirements document says that schemas shall be "more expressive than
DTDs".  By this we mean that schemas will be a superset of DTDs  in generative
power.  As for readability, schemas will have XML syntax and I judge that to be
more
readable than DTDs but that's a personal preference.

2. Reuse mechanism simpler than inheritance
Several people have asked for mechanisms other than inheritance that would
further
reuse.  This is currently under investigation by the design team.

3. Remove entity definitions from schema language.
This, too, is a design issue and is being considered by the design team.

4. Datatype requirement 2 may be too hard.
There are several issues re. mapping from databases to XML.  We are attacking
some of them.  For example, we are defining datatypes that enable simple mapping
from database values to XML.  The issue of keys is a thorny one.  I personally
believe
that the ID/IDREF mechanism in XML is not adequate as a general reference
mechanism and would like to see something better but I am not sure we will step
up
to representing primary keys and foriegn keys in the first draft.

Thank you for your comments.

All the best, Ashok Malhotra
Received on Friday, 9 April 1999 09:54:50 GMT

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