We resolved 6721 (attaching policy to implicit operations) by introducing a new WS-MetadataExchange dialect for each specification in order to retrieve its WSDL.  For example, we introduced the following dialect IRI for WS-Transfer: http://www.w3.org/2009/02/ws-tra/TransferWSDL

We did not consider simply using the existing WSDL dialect with the namespace as an identifier. I.e. in order to acquire the WS-Transfer WSDL, the GetMetadata request could look like this:


   <mex:GetMetadata>
      <mex:Dialect URI="http://schemas.xmlsoap.org/wsdl"
         Identifier="http://www.w3.org/2009/09/ws-tra"/>
   </mex:GetMetadata>

The advantages to this approach are:

1) There is no need to define a new dialect in each specification.  The behaviour is defined entirely in WS-MetadataExchange.  Hence we have a solution applicable to all specs whose operations may be implicit, even if they are not part of the WS-RA group of specifications.  

2) The WS-MetadataExchange spec states:

 "If there is more than one metadata unit with the same Dialect, e.g., more than one XML Schema document, including them all, one per Metadata Section, is explicitly encouraged." 

This means that a client could receive all the WSDLs it needed in order to establish the policy of a Web service exchange (that is: the WSDLs for both the explicit and implicit operations) via a single GetMetadata call.  With the current solution, a client needs to get the 'main' WSDL via GetMetadata, establish a list of the implicit operations, and then issue another GetMetadata to get the implicit operation WSDL.

Side note: this highlights a problem that's already existing in the Metadata spec: when multiple WSDL documents are returned from GetMetadata, how do we distinguish the 'real' one - i.e. the one that would be returned from HTTP GET targeted at <endpoint>?WSDL ?  We could address this problem under this issue or under a new one.

3) I think that the spec may have already allowed for this behaviour(!!) and we may have over-engineered the solution to 6721.  Therefore, we may inadvertently have 2 solutions for the same problem, leading to potential interoperability concerns.

Proposal :
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Explicitly state in the WS-MetadataExchange specification that the use of the WSDL dialect combined with the appropriate identifier may be used in order to acquire the WSDL(s) of any implicit operations.  

Remove the definitions of the dialect IRIs that we added to the individual specs as part of 6721.