[ogsa-wg] Virtualization: How do we specify notifications?

[Michael Behrens]

Interesting Dave....
I understand that properties can be queried using WS-ResourcePropoerties 
and can be advertised (pub/sub) via WS-Notification.   However does not 
WSRF separate the properties from the methods - almost in a non-OO 
fashion? (de-encapsulate)    I'm not sure if there is an automatic 
association between properties defined and notification events as this 
might be optionally implemented.  So perhaps this needs to be specified 
if needed along with the identifiers of the properties in the profile 
documents.  What about thread control (locking, etc?) issues?

A side note with regard to APIs and SOA:  It does seem as though an 
adhoc refactoring of APIs (MFC, Java, others) are being created as Web 
Services.  WSRF brings state with it, and hence ways to instantiate 
object properties dynamically.  Not behavior however.  Perhaps an 
introduction of WS-Rules or WS-Class (just made those up) or perhaps 
something in BPEL or Web Services Choreography Description Language 
(WS-CDL) would provide a linkage between the properties and behavior.  
It seems like the OO lessons are slowing being re-learned in the WS* space.
If we were to refactor the grid fabric with an interoperable 
standardized language as a goal, one might question if SOAP and the 
entire WS* stack should be used as that basis.  For now, it is a good 
foundation (language interop), however I would like to see what else 
might be possible with regard to OO based grid specs which could be 
standardized via the GGF, perhaps using a model (as in Model Drivel 
Architecture).

Dave Berry wrote:

>Dear OGSA WG,
>
>In the object-oriented world, components such as Java Beans or ActiveX
>controls are typically defined by a set of properties, a set of methods
>and a set of events.  In the service-oriented world we have a similar
>requirement, dealing with interoperable messages rather than a language
>API.  What is the best way to specify the notifications that a service
>or interface can send?  
>
>The OGSA document describes a virtualization as a "common set of
>abstract interfaces available for a set of similar resources, thereby
>hiding differences in their properties and operations".  To this we
>somehow have to add the notifications that can be generated, as these
>are an essential part of virtualization.  Are the notifications part of
>an interface?  Are they actually specified in any of the metadata for a
>service?
>
>The OGSA document defines an interface as follows: "In a
>service-oriented architecture, a specification of the operations that a
>service offers its clients".  Should this be extended to include
>properties and/or notifications?
>
>This is a live issue for the Data Architecture document.
>
>Best wishes,
>
>Dave Berry
>Research Manager, National e-Science Centre
>15 South College St., Edinburgh
>Tel: +44 131 6514039
>
>
>
>  
>

-- 
Michael Behrens
R2AD, LLC
(571) 594-3008 (cell) *new*
(703) 714-0442 (land)