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Proposal: Nested WS-Policy Assertions for WS-Addressing

From: David Illsley <david.illsley@uk.ibm.com>
Date: Wed, 6 Dec 2006 14:50:48 +0000
To: public-ws-addressing@w3.org
Message-ID: <OFA92097B7.05BD6BBA-ON8025723C.00506B86-8025723C.00518D38@uk.ibm.com>

Nested WS-Policy Assertions for WS-Addressing

Below is my proposal (borrowing heavily from the previous proposal), 
followed by examples in compact and normal form. I believe that inclusion 
in the specification of at least some of the examples in compact form 
would be of benefit. As stated on the call I have used the name 
wsaw:AddressingRequired for the container assertion rather than 
wsaw:UsingAddressing as it's unclear if we can and we can have that 
discussion separately. I've also left the issue of which policy subject(s) 
to specify to be dealt with on the existing thread - "WS-Addr policy 
attachment"

David

3.2 WS-Policy Assertions

The other mechanism for indicating that a binding or endpoint [ note: open 
issue on policy attachment options ] conforms to the WS-Addressing 
specification is through the use of the Web Services Policy - Framework 
[WS-Policy] and Web Services Policy - Attachment [WS-PolicyAttachment] 
specifications. [ insert appropriate references ]. This specification 
defines the following three policy assertions:

3.2.1 AddressingRequired Assertion

The wsaw:AddressingRequired policy assertion is a nested policy container 
assertion. The meaning of this assertion when present in a policy 
alternative is that WS-Addressing is required to communicate with the 
subject. In order to indicate that the subject supports WS-Addressing but 
does not require its use, an additional policy alternative should be 
provided which does not contain this assertion. This may be done in 
WS-Policy compact form by adding the attribute wsp:Optional="true" to the 
AddressingRequired assertion. 

3.2.1 AnonymousResponses Assertion

This element MAY be used as a policy assertion nested within the 
AddressingRequired assertion in accordance with the rules laid down by 
WS-Policy Framework 1.5 section 4.3.2. The appearance of this element 
within a policy alternative indicates that the endpoint will accept 
request messages with response endpoint EPRs that contain the anonymous 
URI ("http://www.w3.org/2005/08/addressing/anonymous") as the value of 
[address]. The absence of the wsaw:AnonymousResponses policy assertion 
within a policy alternative does *not* indicate that the endpoint will not 
accept
request messages with response endpoint EPRs that contain the anonymous 
URI as an address; it simply indicates the lack of any affirmation of 
support for anonymous URIs.

3.2.2 NonAnonymousResponses Assertion

This element MAY be used as a policy assertion nested within the 
AddressingRequired assertion in accordance with the rules laid down by 
WS-Policy Framework 1.5 section 4.3.2. The appearance of this element 
within a policy alternative indicates that the endpoint will accept 
request messages with response endpoint EPRs that contain something other 
than the anonymous URI as the value of [address]. This assertion is 
deliberately vague; 
it's presence indicates that a non-anonymous addresses might be accepted 
but doesn't constrain what such an address might look like. A receiver can 
still reject a request that contains an address that it doesn't understand 
or that requires a binding it doesn't support. As with the other 
assertions, the absence of the wsaw:NonAnonymousResponses policy assertion 
within a policy alternative does *not* indicate that the endpoint will not 
accept request messages with response endpoint EPRs that contain something 
other than the anonymous URI address.

NOTE: If both AnonymousResponses and NonAnonymousResponses are supported 
and the intention is to allow either to be used care should be taken to 
ensure there is an alternative which includes just AnonymousResponses as a 
nested assertion and an alternative with just NonAnonymousResponses as a 
nested assertion so that a subject which supports only one will have a 
compatible policy [WS-Policy Primer 3.4] (e.g. 3, 4 below).

Also, given that the lack of either of these assertions 
(AnonymousResponses and NonAnonymousResponses) does not indicate lack of 
support, it is suggested that a subject that does not have a strict 
compatibility requirement that an interacting subject understands or is 
concerned with these assertions provides an alternative without either 
assertion (e.g. 3 below).

3.2.3 Examples (Compact Form)

1. Subject supports addressing, no statement on supported response EPRs
<wsp:Policy>
        <wsaw:AddressingRequired wsp:Optional="true">
                <wsp:Policy></wsp:Policy>
        </wsaw:AddressingRequired>
</wsp:Policy>

2. Subject requires addressing be used, no statement on supported response 
EPRs
<wsp:Policy>
        <wsaw:AddressingRequired>
                <wsp:Policy></wsp:Policy>
        </wsaw:AddressingRequired>
</wsp:Policy>

3. Subject supports addressing, explicitly (and optionally) supports anon 
and non-anon response EPRs
<wsp:Policy>
        <wsaw:AddressingRequired wsp:Optional="true">
                <wsp:Policy>
                        <wsaw:AnonymousResponses wsp:Optional="true" />
                        <wsaw:NonAnonymousResponses wsp:Optional="true" />
                </wsp:Policy>
        </wsaw:AddressingRequired>
</wsp:Policy>

4. Subject requires addressing, requires explicit support of anon or 
non-anon
<wsp:Policy>
        <wsaw:AddressingRequired>
                <wsp:Policy>
                        <wsp:ExactlyOne>
                                <wsaw:AnonymousResponses />
                                <wsaw:NonAnonymousResponses />
                        </wsp:ExactlyOne>
                </wsp:Policy>
        </wsaw:AddressingRequired>
</wsp:Policy>

5. Subject requires addressing and use of non-anon response EPRs
<wsp:Policy>
        <wsaw:AddressingRequired>
                <wsp:Policy>
                        <wsaw:NonAnonymousResponses />
                </wsp:Policy>
        </wsaw:AddressingRequired>
</wsp:Policy>

Examples (Normal Form)

1. Subject supports addressing, no statement on supported response EPRs
<wsp:Policy>
        <wsp:ExactlyOne>
                <wsp:All/>
                <wsp:All>
                        <wsaw:AddressingRequired>
                                <wsp:Policy>
                                        <wsp:ExactlyOne>
                                                <wsp:All />
                                        </wsp:ExactlyOne>
                                </wsp:Policy>
                        </wsaw:AddressingRequired>
                </wsp:All>
        </wsp:ExactlyOne>
</wsp:Policy>

2. Subject requires addressing be used, no statement on supported response 
EPRs
<wsp:Policy>
        <wsp:ExactlyOne>
                <wsp:All>
                        <wsaw:AddressingRequired>
                                <wsp:Policy>
                                        <wsp:ExactlyOne>
                                                <wsp:All />
                                        </wsp:ExactlyOne>
                                </wsp:Policy>
                        </wsaw:AddressingRequired>
                </wsp:All>
        </wsp:ExactlyOne>
</wsp:Policy>

3. Subject supports addressing, explicitly (and optionally) supports anon 
and non-anon response EPRs
<wsp:Policy>
        <wsp:ExactlyOne>
                <wsp:All/>
                <wsp:All>
                        <wsaw:AddressingRequired>
                                <wsp:Policy>
                                        <wsp:ExactlyOne>
                                                <wsp:All />
                                        </wsp:ExactlyOne>
                                </wsp:Policy>
                        </wsaw:AddressingRequired>
                </wsp:All>
                <wsp:All>
                        <wsaw:AddressingRequired>
                                <wsp:Policy>
                                        <wsp:ExactlyOne>
                                                <wsp:All>
 <wsaw:AnonymousResponses />
                                                </wsp:All>
                                        </wsp:ExactlyOne>
                                </wsp:Policy>
                        </wsaw:AddressingRequired>
                </wsp:All>
                <wsp:All>
                        <wsaw:AddressingRequired>
                                <wsp:Policy>
                                        <wsp:ExactlyOne>
                                                <wsp:All>
 <wsaw:NonAnonymousResponses />
                                                </wsp:All>
                                        </wsp:ExactlyOne>
                                </wsp:Policy>
                        </wsaw:AddressingRequired>
                </wsp:All>
                <wsp:All>
                        <wsaw:AddressingRequired>
                                <wsp:Policy>
                                        <wsp:ExactlyOne>
                                                <wsp:All>
 <wsaw:AnonymousResponses />
 <wsaw:NonAnonymousResponses />
                                                </wsp:All>
                                        </wsp:ExactlyOne>
                                </wsp:Policy>
                        </wsaw:AddressingRequired>
                </wsp:All>
        </wsp:ExactlyOne>
</wsp:Policy>

4. Subject requires addressing, requires explicit support of anon or 
non-anon
<wsp:Policy>
        <wsp:ExactlyOne>
                <wsp:All>
                        <wsaw:AddressingRequired>
                                <wsp:Policy>
                                        <wsp:ExactlyOne>
                                                <wsp:All>
 <wsaw:AnonymousResponses />
                                                </wsp:All>
                                        </wsp:ExactlyOne>
                                </wsp:Policy>
                        </wsaw:AddressingRequired>
                </wsp:All>
                <wsp:All>
                        <wsaw:AddressingRequired>
                                <wsp:Policy>
                                        <wsp:ExactlyOne>
                                                <wsp:All>
 <wsaw:NonAnonymousResponses />
                                                </wsp:All>
                                        </wsp:ExactlyOne>
                                </wsp:Policy>
                        </wsaw:AddressingRequired>
                </wsp:All>
        </wsp:ExactlyOne>
</wsp:Policy>

5. Subject requires addressing and use of non-anon response EPRs
<wsp:Policy>
        <wsp:ExactlyOne>
                <wsp:All>
                        <wsaw:AddressingRequired>
                                <wsp:Policy>
                                        <wsp:ExactlyOne>
                                                <wsp:All>
 <wsaw:NonAnonymousResponses />
                                                </wsp:All>
                                        </wsp:ExactlyOne>
                                </wsp:Policy>
                        </wsaw:AddressingRequired>
                </wsp:All>
        </wsp:ExactlyOne>
</wsp:Policy>

David Illsley
Web Services Development
MP211, IBM Hursley Park, SO21 2JN
+44 (0)1962 815049 (Int. 245049)
david.illsley@uk.ibm.com
Received on Wednesday, 6 December 2006 14:51:05 GMT

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