New Item - Clarify Input Context Usage

Section 6.1 begins:

The <Request> element is a top-level element in the XACML context schema.
The <Request> element is an abstraction layer used by the policy language.
Any proprietary system using the XACML specification MUST transform its
decision request into the form of an XACML context <Request>.

I believe this should be changed to:

The <Request> element is a top-level element in the XACML context schema.
The <Request> element is an abstraction layer used by the policy language.
For simplicity of expression, this document describes policy evaluation in
terms of operations on the context. However a conforming PDP is not required
to actually instantiate the context in the form of an XML document. But, any
system conforming to the XACML specification MUST produce exactly the same
decisions as if all the inputs had been transformed into the form of an
XACML context <Request>.

Hal