Title

Clarify restrictions of ID type usage


Description

With issue 3560 we added a new xml:id to the Policy element: "/wsp:Policy/(@wsu:Id | @xml:id)"

Both wsu:Id and xml:id are assigned the ID type and must meet its constraints.


Justification

It is not obvious to developers that are not intimately familiar with XML what the constraints of the ID type are and that they need to take it into account. A normative reference would be helpful.


Target

Web Services Policy Framework, section 2.1


Proposal

Extend this text in section 4.2:

/wsp:Policy/(@wsu:Id | @xml:id)

    The identity of the policy expression as an ID within the enclosing XML document.
If omitted, there is no implied value. To refer to this policy expression, an
IRI-reference MAY be formed using this value per Section 4.2 of WS-Security [WS-Security 2004]
when @wsu:Id is used.

with:

/wsp:Policy/(@wsu:Id | @xml:id)

    The identity of the policy expression as an ID within the enclosing XML document. 
If omitted, there is no implied value.
The constraints of the [XML 1.0] ID type MUST be met.
To refer to this policy expression, an IRI-reference MAY be formed using this value
per Section 4.2 of WS-Security [WS-Security 2004] when @wsu:Id is used.