Fwd: Comments on the preview of the WS-MetadataExchange Working Draft

fwd to public comments list

Begin forwarded message:

> Resent-From: public-ws-resource-access@w3.org
> From: Antoine Mensch <antoine.mensch@odonata.fr>
> Date: October 13, 2009 1:59:38 PM PDT
> To: public-ws-resource-access@w3.org
> Subject: Comments on the preview of the WS-MetadataExchange Working  
> Draft
> Reply-To: antoine.mensch@odonata.fr
>
> Dear colleagues,
>
> Please find below some comments on the preview of the WS- 
> MetadataExchange Working Draft (http://www.w3.org/TR/2009/WD-ws-metadata-exchange-20090924 
> ).
>
> I. Section 7
>
> This section provides a way to attach metadata to an EPR.  However,  
> the spec does not clearly state whether this feature is only  
> intended for carrying general metadata about the service exposed  
> through the endpoint (as the examples seem to indicate), or whether  
> it could also be used for carrying endpoint-specific metadata, such  
> as the endpoint effective policy (as defined in WS-PolicyAttachment).
>
> Ideally, there should be an easy way to directly attach an endpoint  
> effective policy to the EPR, in order to bypass the usual complex  
> algorithm that the client must implement to compute the endpoint  
> effective policy, which is not practical for some embedded clients:
> 1) Download the WSDL
> 2) Retrieve the service port corresponding to the EPR (matching the  
> address, and hoping that the WSDL is complete, i.e. is dynamically  
> generated by the service to contain an up-to-date address, which is  
> often numerical in cases of devices).
> 3) Build the endpoint effective policy by merging info extracted  
> from the WSDL and possibly an external policy document.
>
> The closest way I can see in the current version of the spec would  
> be to use an external policy attachment as metadata section, using  
> the EPR as policy scope. So for instance, to express that an EPR  
> supports the DPWS requirements for hosted services (as a basic  
> example of policy assertion), one could have:
>
> <wsa:EndpointReference
>  xmlns:wsa='http://www.w3.org/2005/08/addressing'>
> <wsa:Address>http://192.168.0.34/myHostedService</wsa:Address>
> <wsa:Metadata>
>  <mex:Metadata xmlns:mex='http://www.w3.org/2009/09/ws-mex'>
>    <mex:MetadataSection xmlns:wsp='http://www.w3.org/ns/ws-policy'>
>        Dialect='http://www.w3.org/TR/ws-policy-attach'>
>      <wsp:PolicyAttachment>
>        <wsp:AppliesTo>
>          <wsa:EndpointReference>
>            <wsa:Address>http://192.168.0.34/myHostedService</ 
> wsa:Address>
>          </wsa:EndpointReference>
>        </wsp:AppliesTo>
>        <wsp:Policy>
>          <dpws:Profile xmlns:dpws='http://docs.oasis-open.org/ws-dd/ 
> ns/dpws/2009/01'/>
>        </wsp:Policy>
>      </wsp:PolicyAttachment>
>    </mex:MetadataSection>
>  </mex:Metadata>
> </wsa:Metadata>
> </wsa:EndpointReference>
>
> Is the above a valid use of the EPR embedded metadata feature?
>
> If so, although much simpler than having to parse a full WSDL, it  
> remains a relatively heavy solution for embedded clients. A simpler  
> solution could be to have, by specifying that the EPR defines a  
> default policy scope, and thus avoiding the external policy  
> attachment construct:
>
> <wsa:EndpointReference
>  xmlns:wsa='http://www.w3.org/2005/08/addressing'>
> <wsa:Address>http://192.168.0.34/myHostedService</wsa:Address>
> <wsa:Metadata>
>  <mex:Metadata xmlns:mex='http://www.w3.org/2009/09/ws-mex'>
>    <mex:MetadataSection xmlns:wsp='http://www.w3.org/ns/ws-policy'>
>        Dialect='http://www.w3.org/TR/ws-policy'>
>      <wsp:Policy>
>        <dpws:Profile xmlns:dpws='http://docs.oasis-open.org/ws-dd/ns/ 
> dpws/2009/01'/>
>      </wsp:Policy>
>    </mex:MetadataSection>
>  </mex:Metadata>
> </wsa:Metadata>
> </wsa:EndpointReference>
>
> or even better (allowing any predefined WS-Mex dialect to appear in  
> the WS-Addressing metadata, as in a Get response)
>
> <wsa:EndpointReference
>  xmlns:wsa='http://www.w3.org/2005/08/addressing'>
> <wsa:Address>http://192.168.0.34/myHostedService</wsa:Address>
> <wsa:Metadata>
>  <wsp:Policy>
>    <dpws:Profile xmlns:dpws='http://docs.oasis-open.org/ws-dd/ns/ 
> dpws/2009/01'/>
>  </wsp:Policy>
> </wsa:Metadata>
> </wsa:EndpointReference>
>
>
> II. Editorial comments:
>
> It seems that the namespace used in schema import elements in  
> several examples should be http://services.example.org/stockquote/schemas 
>  instead of http://services.example.org/stockquote
>
> Best regards,
>
> Antoine Mensch
>