Re: [wsrf] WS-RAP; section 2.3 - WS-Resource definition

[David Snelling <David.Snelling@UK.Fujitsu.com>]

Folks,

This issue has come up in other discussions I have had, particularly  
with folks less enthusiastic about WSRF. Put generally ...

If I have a WS and a bunch of resources, I have a set of WS-Resources  
with a one-to-one correspondence to the resources. Because all the  
WS-Resources share the same WS they can respond to the operations.  
Rich's question (and that of others) is, can I drive the same operation  
on all WS-Resources at once?

Answer 1: Yes, create a new Disambiguator that refers to the whole  
collection. Steve pointed to this option.

Answer 2: Wrap the set of WS-Resources in a ServiceGroup and drive the  
operation on all WS-Resources through an iterator operation on the  
ServiceGroup (NB: such an iterator has yet to be proposed for  
ServiceGroup).

Answer 3: Allow multiple Disambiguators in a single message. To use  
embodiment 1, create an EPR for the collection that looked like this:

<wsa:EndpointReference>
     
<wsa:Address>http://localhost:8080/axis/services/UnicorePort</wsa: 
Address>
    <wsa:ReferenceProperties>
       <ns1:ResourceDisambiguator xmlns:ns1="http://arcon.fujtsu.com/";>
	    UnicorePort:E5623340-16DA-11D9-9A2A-C83D27C15A63
       </ns1:ResourceDisambiguator>
       <ns1:ResourceDisambiguator xmlns:ns1="http://arcon.fujtsu.com/";>
	    UnicorePort:0035B930-16DB-11D9-9A2A-9A608286117E
       </ns1:ResourceDisambiguator>
    </wsa:ReferenceProperties>
</wsa:EndpointReference>

The semantics would require that the client copy both Disambiguators  
into the message and the service could interpret this as "Drive the  
same operation on all the WS-Resources referenced by the Disambiguators  
in the message."

I kind of like this, but I have never been convinced by WSRF critic's  
use cases. Possibly the WSRP use case is a strong enough one.

Note: I don't believe this approach is as straight forward for the  
other embodiments as the above.


On 5 Oct 2004, at 23:18, Rich Thompson wrote:

>
> One of the things I appreciate about the definition set in WS-RAP is  
> that it clearly separates a resource from a WS-Resource. I agree that  
> the portlet is a WS-Resource, but it is encapsulating multiple  
> resources rather than multiple WS-Resources. The essence of my  
> question is whether the web service endpoint is allowed to operate on  
> multiple resources or whether there is a strict one-to-one mapping of  
> resource to WS-Resource. Clearly the portlet could invent a wrapper  
> resource that merely encapsulates the underlying resources, but why  
> should that be required?
>
> On the ramifications of allowing this broadening, I think we all agree  
> that this can be done without the client being aware of it. The client  
> is interacting with a WS-Resource and it has no idea of the meaning of  
> the various parts (could include a separate identifier for each  
> resource) of the endpoint that it has been given, only that it has to  
> follow the contract of the binding to the WS-Resource that is in use.
>
>  Rich
>
>
>
>
> Tom Maguire/Hawthorne/IBM@IBMUS
>
> 10/05/2004 02:56 PM
>
> To
> Rich Thompson/Watson/IBM@IBMUS
>
> cc
> wsrf@lists.oasis-open.org
>
> Subject
> Re: [wsrf] WS-RAP; section 2.3 - WS-Resource definition
>
>
>
>
>
>
>
>
>
>
>
>  So I guess I'm struggling with this a bit.  From the client's  
> perspective
>  you have a single
>  WS-Resource.  That WS-Resource has an identifier.  As you mentioned  
> the
>  client would
>  not need to know or care that multiple resources are involved.  In WS
>  Remote Portlet it
>  sounds as if there is a need to do a composition of multiple  
> (different
>  types of )
>  WS-Resources and the "portlet" endpoint is responsible for dispatch  
> to the
>  underlying
>  "encapsulated" WS-Resources.  In this model I think the WS-Resource  
> is the
>  remote portlet.
>  That remote portlet has its own identifier.  That identifier is used  
> as a
>  resource disambiguator
>  to the "collection" of related WS-Resources not to the individual
>  WS-Resources of the collection.
>
>  So I agree that clients should not care but I would also argue then  
> that
>  from the clients
>  perspective there is just one WS-Resource and that the definition of a
>  WS-Resource
>  is correct from that perspective.
>
>  Tom
>
>  Problems cannot be solved at the same level of awareness that created
>  them.  —Albert Einstein
>  T o m   M a g u i r e
>
>  STSM, On Demand Architecture
>  Poughkeepsie, NY  12601
>
>  Rich Thompson/Watson/IBM@IBMUS wrote on 10/05/2004 01:43:27 PM:
>
>  >
>  > Not quite our situation. Certain operations will need to access more
>  > than one resource during the processing of a single message. How the
>  > set of resources is constructed and referenced by the endpoint would
>  > be a matter between the factory and the resource disambigurator. I
>  > would hope the client would not need to know or care that multiple
>  > resources are involved and am raising the case seeking that both the
>  > language and semantics permit such a pairing of a web service and a
>  > set of resources within a single endpoint without requiring
>  > knowledgeable clients.
>  >
>  > Rich
>  >
>
>  >
>  > Steve Graham/Raleigh/IBM
>  > 10/05/2004 09:51 AM
>  >
>  > To
>  >
>  > Rich Thompson/Watson/IBM@IBMUS
>  >
>  > cc
>  >
>  > wsrf@lists.oasis-open.org
>  >
>  > Subject
>  >
>  > Re: [wsrf] WS-RAP; section 2.3 - WS-Resource definitionLink
>  >
>  >
>  >
>  > Rich:
>  > To clarify, your situation is such that a Web service deployed at
>  > some URL is the access point for a collection (potentially many)
>  resources?
>  >
>  > Given my assumption is true, I don't see why you have come to the
>  > conclusion that the definition of WS-Resource precludes it.  The
>  > examples in the WSA embodiments (sections 3.1 and 3.2) suggest this
>  > pattern where a single web service is front ending 2 resources.
>  > Note that it is the pair (web service + resource) that is the WS-
>  > Resource. So in the examples in the WSA embodiments contain 2
>  WS-Resources.
>  >
>  > Does this help?
>  >
>  > ++++++++
>  > Steve Graham
>  > (919)254-0615 (T/L 444)
>  > STSM, On Demand Architecture
>  > Member, IBM Academy of Technology
>  > <Soli Deo Gloria/>
>  > ++++++++
>  >
>  >
>  > Rich Thompson/Watson/IBM@IBMUS wrote on 10/05/2004 08:53:02 AM:
>  >
>  > > While I haven't finished working through exactly how the WSRP
>  > protocol could best
>  > > leverage WSRF, I (and others on the WSRP TC) are leaning towards
>  > the at least some
>  > > of the web service endpoints containing references to a set of
>  > resources rather
>  > > than just one. The proposed definition ("A WS-Resource is a Web
>  > service through
>  > > which a resource can be accessed.") excludes such use cases. Any  
> reason
>  the
>  > > definition can not be broadened to "A WS-Resource is a Web service
>  > through which a
>  > > set of one or more resources can be accessed." This would carry
>  > into many other
>  > > places in the text where the resource is referred to in the  
> singular.
>  > > Rich Thompson
>  > > OASIS WSRP TC Chair
>
-- 

Take care:

     Dr. David Snelling < David . Snelling . UK . Fujitsu . com >
     Fujitsu Laboratories of Europe
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