[xacml] MK01: DataType and Namespace

We have agreed to specify DataType attribute in both policy and context.
The schema 16j says that DataType attribute is xs:anyURI. I think that the
DataType is written as QName such as "xs:string" and "xs:boolean" like
MatchId attribute. So I request to change DataType attribute from xs:anyURI
to xs:QName. Besides, we should add the following namespace prefix and its
namespace URI in the spec.

Prefix            Namespace URI
xacml-function    urn:oasis:names:tc:xacml:1.0:function
xacml-datatype    urn:oasis:names:tc:xacml:1.0:datatype

*) datatype prefix is used for xacml-datatype:x500Name and
xacml-datatype:rfc822Name. In fact, prefix itself matters only in the
specification document. Policy writers can choose another prefix as they
like.

I think text that refers to ds: prefix (XML Signature namespace) and saml:
prefix no longer exist in the spec. So line 289-290, 303-305  should be
deleted.

Michiharu Kudo

IBM Tokyo Research Laboratory, Internet Technology
Tel. +81 (46) 215-4642   Fax +81 (46) 273-7428