the composite ID attribute

Hi,,,

The concept of composite key which is available in Relational Database is it also available in the XML DTD or XML RDF?  ..I tried to declare an element attributes of a course relation as the following:

 1. <!ELEMENT  COURSE (course_id, dep_id , title, units)>

   2.  <!ATTLIST  COURSE  (course_id, dep_id) ID    # REQUIRED> 

as you can see  the two attributes course_id and dep_id  of the main Element (relation) COURSE are key (composite key) .

my question: Is the syntax of line no.2 right or not and why?

  Regards

-AbuKalam



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