Hi Marvin,
 
It seems strange to me to limit yourself to a list of identifiers as a means of interacting with large numbers of jobs.  Wouldn't it be more flexible to allow more complex expressions, such as "all jobs submitted by Marvin that use more than 4 processors and are currently running" (or whatever).  You could build an appropriate information model, map it to a data model and provide a corresponding query language that clients could use to request the information they need.

I agree that this is a service-oriented approach rather than a resource-oriented approach.  However, having set up a particular query, you might want to repeatedly interact with the current state of that query.  So it might make sense to register the query with the service and return an EPR that can be used to get the current set of results.
 
I don't see much point in passing back an abstract name (e.g. a UUID) on its own.  Without a reference to a resolution mechanism, clients won't be able to make much use of it.  This is why URL's and URI's have been so successful; they include enough information for any client to know which mechanism to use to resolve them.  This seems to be one advantage of the WS-Name proposal; it includes an abstract name with a reference to a resolution mechanism. 
 
Is it still the case that BES containers are allowed (or even encouraged) to return WS-Names?
 
Would it be useful to have a means for composing WS-Name EPRs that use the same resolution mechanism in order to make a single WS-Name that can be used to query all of them?
 
Dave.
 
 
 
 
-----Original Message-----
From: owner-ogsa-wg@ggf.org [mailto:owner-ogsa-wg@ggf.org] On Behalf Of Marvin Theimer
Sent: 29 April 2006 03:06
To: ogsa-wg@ggf.org
Subject: [ogsa-wg] Thoughts on extensions mechanisms for the HPC profile work

·        Support for array operations and other forms of batching.

·        When 1000’s of jobs are involved the efficiency gains of employing array operations for things like queries or abort requests are too significant to ignore.  Hence a model in which every job must be interacted with on a strictly individual basis via an EPR is arguably unacceptable.

·        One approach would be to simply add array operations alongside the corresponding individual operations, so that one can selectively interact with jobs (as well as things like data files) in either an “object-oriented” fashion or in “bulk-array” fashion.

One could observe that the array operations enable the corresponding individual operations as a trivial special case, but this would arguably violate the principle of defining a minimalist base case and then employing only extensions (rather than replacements).

·        Array operations are an example or a service-oriented rather than a resource-oriented form of interaction: clients send a single request to a job scheduler (service) that refers to an array of many resources, such as jobs.  This raises the question of whether things like jobs should be referred to via EPRs or via unique “abstract” names that are independent of any given service’s contact address.  At a high level, the choice is unimportant since the client submitting an array operation request is simply using either one as a unique (and opaque) identifier for the relevant resource.  On a pragmatic level one might argue that abstract names are easier and more efficient to deal with than EPRs since the receiving scheduler will need to parse EPRs to extract what is essentially the abstract name for each resource.  (Using arrays of abstract names rather than arrays of EPRs is also more efficient from a size point-of-view.)

·        If abstract names are used in array operations then it will necessary that individual operations return the abstract name and not just an EPR for a given resource, such as a job.  If this approach is chosen then this implies that the base case design and implementation must return abstract names and not just EPRs for things like jobs.