[ogsa-wg] Thoughts on extensions mechanisms for the HPC profile work

[Karl Czajkowski]

On May 03, Donal K. Fellows modulated:
...
> On the other hand, I question the extent to which an optional resource
> requirement has any real meaning anyway. The only times I can see a use
> are for when you're really trying to capture some other sense of
> resource by proxy, such as asking for certain operating systems with an
> explicit executable path instead of asking for the abstract application
> name that is installed at that location on those systems. But I feel
> that people should not ask for such proxies for what they desire; they
> should say what they really need (Blast, Gaussian, etc.) and let the
> middleware take the strain.

But aren't we defining standards for the middleware to follow (and not
necessarily the people)?  I think it is a HUGE mistake to keep talking
about these standards efforts as if they are human interfaces.  That
will not give us the robust machine-to-machine communication we
require, including the ability to evolve in place etc.  Human
information consumers are too flexible and adaptable to be the
evaluation criteria for whether a protocol is going to be robust
between heterogeneous software agents...

The point of the "optional extension" is to allow software components
to behave with graceful degradation in a heterogeneous environment.
If there are basic and extended ways to describe what the client
software wants/needs and the extended one is "better" but not critical
to function, this allows the single message exchange to express all of
that and get the best available behavior.

So, I think "may ignore, but should try not to" is about the right
semantics for this flag. :-) I agree that critical handling is the
appropriate default for extensions.  My main point is that the
criticality of the extension is instance-specific to the use and NOT
usually a characteristic of the extended concept itself.


karl

-- 
Karl Czajkowski
karlcz at univa.com