[ogsa-bes-wg] EPR as activity identifier

[William Lee]

Hi all,

I have hit on a couple of issues raised during my implementation effort 
regarding the use of EPR in BES. I will try to write down my 
interpretation here so the group can correct me.

Issue 1: What the type of the service addressed by the EPR returned from 
a CreateActivityFromJSDL request?

[Section 5] suggests the type of the service is out of the scope of BES. 
However, it hasn't addressed the fact that an activity might not even 
have a service representing it. If I implement this hypothetical BES 
service, what should I put in the <wsa:Address/> element?

Issue 2: Should a <bes:activity-identifier/> (currently an EPR) be 
totally opaque to users other than the issuer (the BES service)?

If the client does not understand how or even wish to interact with the 
service referenced by the EPR, the <bes:activity-identifier/> is 
completely opaque because they are simply copied into the bodies of 
GetActivityStatus, RequestActivityStateChanges and 
GetActivityJSDLDocuments. There's no need for the content to be 
introspected.

If the client wishes to interact with the service referenced by the EPR 
(and know the type of course), the <bes:activity-identifier/> will serve 
as both the address and the identifier (a <wsa:ReferenceProperties/>?) 
to the activity. I can only interact with the activity through the 
service (e.g. POSIXControlService) addressed by that EPR. Even though 
there might be a third service (at a different <wsa:Address/> and 
different type [MonitoringService]) that can interact with my activity. 
I can't just replace the <wsa:Address> with the new one and stick in the 
original <wsa:ReferenceProperties/> because it's supposed to be opaque. 
How should I perform this resolution?

My point is (if my interpretation is correct) is it a good idea to use a 
service address to identify an activity? If we are not specifying the 
type of the service referenced by the EPR, is there any value in using 
an EPR (instead of ... an IRI)?

William

--- William Lee @  London e-Science Centre, Imperial College London --
--- Software Coordinator ---
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