provision message

Subject: ObjectClassRefType Syntax.

From: Gary P Cole <Gary.P.Cole@Sun.COM>
To: PSTC <provision@lists.oasis-open.org>, Jeff Bohren <jbohren@opennetwork.com>
Date: Tue, 19 Oct 2004 11:25:32 -0500

Draft section 4.1.42.2 currently says that "...an element of type 
ObjectClassRefType
- MAY contain an attribute named "objectclassname" of type xsd:string
- MAY contain an attribute named "elementname" of type QName.

Should we say that an element of ObjectClassRefType
- must have "at least one" of these attributes?
- must have "exactly one" of these attribute?

It would be weird to have *both* attributes. 
It would be useless to have *neither* attribute.