Choices of attributes

[Tony]

How do I to define a tag wit two attributes that
are mutually exclusive?

So I want the tag to look like this:
<COM:description choice1="blah">
or
<COM:description choice2="blahblah">

BUT NOT
<COM:description choice1="blah" choice2="blahblah">

 

[David Carlisle]

How do I to define a tag wit two attributes that
are mutually exclusive?

So I want the tag to look like this:
<COM:description choice1="blah">
or
<COM:description choice2="blahblah">

BUT NOT
<COM:description choice1="blah" choice2="blahblah">

What language do you want to use to make the definition?
XML DTD and W3C XML schema can not express that constraint.
You can express it in Relax NG or schematron for example.

David