Re: [wsrf] issue 127 - : MUST use RAP?

[Ian Robinson <ian_robinson@uk.ibm.com>]

Mark, the WS-Addressing specification itself provides the type definition
of an EPR, some bindings and the normative behaviour with respect to
message information headers. The WS-Addressing statement "this
specification provides no concept of endpoint identity" applies to the
WS-Addressing specification iteslf. WS-RF provides no concept of endpoint
identity either but it does define a particular usage pattern of
WS-Addressing for the concepts we are interested in WS-RF, namely message
exchanges to a WS-Resource through which a specific ResourceProperties XML
document instance may be obtained. The definition in the WS-Resource
specification normatively requires that the EPR must contain sufficient
information for the target endpoint to identify the specific
ResourceProperties document that should be used in the processing of the
request.

The definition of WS-Resource and resource seems quite clear in the
WS-Resource specification, and the TC has been careful to arrive at these
definitions within the scope of WS-RF. There is further background and
additional non-normative material in the Primer document that helps to
explain these concepts.

Regards,
Ian Robinson
STSM, WebSphere Messaging and Transactions Architect
IBM Hursley Lab, UK
ian_robinson@uk.ibm.com


                                                                           
             Mark McKeown                                                  
             <zzalsmm3@nessie.                                             
             mcc.ac.uk>                                                 To 
                                       Ian Robinson/UK/IBM@IBMGB           
             12/08/2005 09:58                                           cc 
                                       wsrf@lists.oasis-open.org           
                                                                   Subject 
                                       Re: [wsrf] issue 127 - : MUST use   
                                       RAP?                                
                                                                           
                                                                           
                                                                           
                                                                           
                                                                           
                                                                           





Hi Ian,
       I am a bit confused about the relationship
between WS-Addressing and WSRF.

The WS-Addressing WG decided that WS-Addressing
EPRs should not be used for identification -
they also think that ReferenceParamaters should
not be used to identify state, rather they should
be used to support stateful interactions (in the
same way HTTP cookies do for HTTP).

http://www.w3.org/2002/ws/addr/ws-issues/#i001

Specifically in the WS-Addressing spec
(http://www.w3.org/TR/2005/WD-ws-addr-core-20050331/) section
2.3 it states "This specification provides no concept of
endpoint identity...."  but the statements below seems to
imply that identity EPRs can be used to provide indentity.

Also I am not clear about the difference/relationship between
a WS-Resource and a resource (as defined by REST or
the W3C Web Architecture document - they effectively define a
resource as anything that can be identified with a URI)


cheers
Mark


> Specifically, replace the bullet at line 127 of WS-Resource with:
>
> ·     "An identifier of the resource MUST be represented in any
reference
> to a WS-Resource and MUST appear as part of any message to a WS-Resource
to
> allow the WS-Resource to disambiguate the resource targeted by the
message.
> We refer to this pattern of access as the “WS-Resource Access Pattern”
> (WS-RAP). The precise location of the resource identifier in a message to
a
> WS-Resource depends on how the identifier is represented in the
WS-Resource
> reference used to access the WS-Resource and also on the
transport-specific
> bindings used to serialize the message."
>
> and update the definition of WS-Resource reference to:
>
> "A WS-Resource reference (or just reference) is a construct through which
a
> single WS-Resource can be accessed. It is represented by an endpoint
> reference, or more precisely an XML element whose type is, or is derived
> (by extension) from the complexType named EndpointReferenceType defined
by
> the [WS-Addressing] specification. The address of the Web service
endpoint
> part of the WS-Resource is contained in the wsa:Address element
information
> item of the endpoint reference. The resource identifier MUST appear
either
> in the contents of the wsa:ReferenceParameter element information item of
> the endpoint reference or embedded as part of the wsa:Address element
> information item of the endpoint reference. In a message that is
conformant
> to the WS-Resource Access Pattern the resource identifier of the resource
> must appear in the message according to binding-specific rules outlined
in
> WS-Addressing. For example, in the SOAP binding defined by WS-Addressing,
> the Web service endpoint address is contained in the wsa:Address element
> information item in the endpoint reference and appears in the message as
> the contents of the wsa:To SOAP header, and each direct child element
> information item (if any) of the wsa:ReferenceParameter element
information
> item appears in the message as a separate SOAP header.
>
>
> For a given resource identifier there may be many references. The way two
> references are compared for equality is implementation-specific and not
> defined by this specification."
>
>
>
>
>
> Attached is a version of WS-Resource with change tracking to illustrate
the
> changes:
>
>
> (See attached file: wsrf-ws_resource-1.2-spec-issue127.doc)
>
>
>
> Regards,
> Ian