W3C Submissions

Datatypes for DTDs Submission: W3C Staff Comment

W3C is pleased to receive the DT4DTD submission from Extensibility, Inc.

During this transitional period of the W3C XML Activity while the XML Schema Working Group develops and deploys their work, this submission provides a valuable mechanism for addressing the lack of data types such as integer, date, etc. in XML 1.0 DTD syntax in a way that is compatible with legacy systems.

However, it relies on a global convention for the interpretation of the unqualified names e-dtype and a-dtype, while use of XML Namespaces would make this unnecessary; using the example from section 1. Datatype Declarations, this might look like:

<!ATTLIST person
   birthdate CDATA #IMPLIED
   height CDATA #IMPLIED
   dt4dtd:e-dtype CDATA #FIXED
   dt4dtd:a-dtype CDATA #FIXED
      "pubdate date
       binding length"

where the choice of dt4dtd as the namespace prefix is arbitrary and can be changed on a per-use basis to avoid collisions with all other names in the DTD.

The use of notations to declare datatypes is quite reasonable given the intended use, but note that the system identifiers such as urn:schemas-microsoft-com:datatypes/int in section 2.2 XML-Data datatypes use an unregistered URN namespace id, schemas-microsoft-com (c.f. URN Syntax (RFC 2141) and URN Namespace Definition Mechanisms (RFC 2611)). As of 13 Nov 1999, Microsoft published documentation on those URNs at http://msdn.microsoft.com/xml/xmlguide/schema-datatypes.asp but they no longer service that address.

The identifiers of the datatypes from XML Schema Part 2: Datatypes (in progress) are available as alternatives to those listed in section 2.2 XML-Data datatypes.

Next Steps

The suggested action of the submission was simply to make it available as a W3C Note, and this is done.

W3C invites discussion of this specification in the various public XML discussion forums.

Dan Connolly
$Revision: 1.6 $ $Date: 2000/01/13 21:21:27 $