New Issue: Policy framework should document extensibility points using {any} and @{any} in xpath-like expressions, and define these in Notational Conventions section

http://www.w3.org/Bugs/Public/show_bug.cgi?id=3590 

(content follows)

Policy framework defines a number of elements that have extensibility
points
for attributes and elements.  In a few places, such as were <assertion>s
can
occur, the extensibility point is documented.  

Every place where extensibility can occur, such extensibility should be
documented.  The places are:
/wsp:Policy/@{any}
/wsp:Policy/.../wsp:PolicyReference/@{any}
/wsp:Policy/.../wsp:PolicyReference/{any}
/wsp:Policy/wsp:ExactlyOne/@{any}
/wsp:Policy/wsp:ExactlyOne/wsp:All/@{any}

Note the first 2 cases have the elipses notation already in the pseudo
schema. 
The remaining places may not be extensibible by design.  

The description of attribute extensibility from attachments is
typically:
Additional attributes MAY be specified but MUST NOT contradict the
semantics of
the owner element; if an attribute is not recognized, it SHOULD be
ignored.

Though I do think the "ignoring" part is redundant with the
extensibility
processing model text.

I propose that:
1. the same notation conventions from the attachment document be
included in
framework
2. the agreed upon extensibility points are documented.

Cheers,
Dave