Internal subset equivalent in new schema proposals?

Michael Kay M.H.Kay at
Wed Dec 2 10:23:27 GMT 1998

>How can you represent a strictly acyclic graph using ID/IDREF?

You make the IDREF attribute optional, and use the absence of a value (the
#IMPLIED default) to indicate a node that has no "parent".

There are many other solutions, e.g. you could have a dummy element with the
special ID value of "NULL", but I can't see why one would want to.

Mike Kay

xml-dev: A list for W3C XML Developers. To post, mailto:xml-dev at
Archived as:
To (un)subscribe, mailto:majordomo at the following message;
(un)subscribe xml-dev
To subscribe to the digests, mailto:majordomo at the following message;
subscribe xml-dev-digest
List coordinator, Henry Rzepa (mailto:rzepa at

More information about the Xml-dev mailing list