[oslc-core] What can an OSLC spec claim? What can a client assume?

[Paul Komar]

Last month Martin Nally wrote "
I think this confirms that the only safe option for a client is to assume
nothing. I think the spec should say this."

Can you please help me understand how a person can implement a client of a
service whose specification is based upon that much ambiguity?
(I got the impression from reading some historical notes from WebDAV client
implementers that while the spec might be written to allow varying degrees
of sophistication of service implementations, they would have preferred a
tighter, more constrained spec.)

Arthur Ryman replied to "I agree that clients should be able to gracefully
handle unexpected
responses."
It seems to me that clients can gracefully decline to provide the desired
behavior when the server doesn't give the client what it needs.

Consider a use case where a client must get information from a service and
then use the information in the response to get more information (possibly
from another service).  If the first service does not provide the requested
information, then the client cannot complete the use case.

Also, I'm curious to learn how to write good compliance tests if the client
can assume nothing.

While the Rest/OSLC world may want to be more flexible than the UML world
(with its effective requirement of transitive closure across domains, as
Martin also wrote about), OSLC services must provide the information in a
consumable way, right?  I thought that the Restful way to handle version
upgrades was to use media types that provided compatible ways to add
information in subsequent versions, but allow older/smaller clients to use
the older/smaller content.

It seems to me that a Rest/OSLC client might have to have a "broader"
expectation of valid responses than an client from the UML world.  (Perhaps
there's an equivalence class of useful responses?)

In summary, I wonder if Martin or Arthur could write up a pattern for good
OSLC client implementations.
Maybe there would be a rule like " don't validate that the response is what
you expect, instead look in the response for the information that you
require"?

--
Paul Komar
Jazz/RTC SCM Developer
Rational Software
IBM Software Group
Littleton, MA
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