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

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