SubjectMatch?

[hao chen <d95776@yahoo.com>]

The example policy of 4.1.1 in XACML Spec v2.0 has the following section for subject matching
769 [a20] <Target>
770 [a21] <Subjects>
771 [a22] <Subject>
772 [a23] <SubjectMatch
773 [a24] MatchId="urn:oasis:names:tc:xacml:1.0:function:rfc822Name-match">
774 [a25] <AttributeValue
775 [a26] DataType="http://www.w3.org/2001/XMLSchema#string";>
776 [a27] med.example.com
777 [a28] </AttributeValue>
778 [a29] <SubjectAttributeDesignator
779 [a30] AttributeId="urn:oasis:names:tc:xacml:1.0:subject:subject-id"
780 [a31] DataType="urn:oasis:names:tc:xacml:1.0:data-type:rfc822Name"/>
781 [a32] </SubjectMatch>
782 [a33] </Subject>
783 [a34] </Subjects>
784 [a35] </Target>
I wonder why the datatype defined in attributeValue tag does not match the datatype defined in SubjectAttributeDesignator. I think logically, the 2 types should be matched/same.

I appreciate if some can explain this to me.

thanks
hao