[GRAAP-WG] Feedback on "Challenges in EU Grid Contracts"

[Karl Czajkowski]

On Aug 29, parkinm at cs.man.ac.uk modulated:

> WS-Agreement is going to be used where these institutions don't exist? Any 
> resource provider (read business) potentially charging for work can't do 
> this in splendid isolation of the existing local regulations and law...
> 

My point was rather that we expect these audit and legal issues to be
"mixed in" by a community that deploys WS-Agreement for a particular
purpose.  I think we've talked around in circles but more or less
observe that the underlying semantics of WS-Agreement are consistent
with typical legal contracting environments.  It may not be complete,
but that is because we did not have the charter to try to standardize
all aspects of discovery, security, audit, nor domain-specific SLA
terminology.


> I presume that what you think may be contestable is whether the contract 
> was actually formed or not if the agreement was never recieved. I think 
> we've covered this.
> 

Yes, and yes.  We're close to counting angels on pins, I'm afraid...



> If the message semantics/schema are defined and agreed to then you should 
> be able to tell the difference and there is no practical ambiguity. If you 
> haven't defined the semantics/schema (or have only partially defined them) 
> then how can you interoperate at all?
>  

I think the WS-Agreement decision semantics are clear, but what the
terms of the SLA actually mean and how these terms bind the two
parties is necessarily domain dependent.  Maybe my philosophy is too
strange for you, but I have trouble defining obligations and trust in
the absence of these domain-dependent concepts.  Keeping my
spec-authoring hat on, I have to remind myself that I do not know how
strongly or weakly the domain-specific terms will capture obligations
between parties when someone applies WS-Agreement in practice.


> >WS-Agreement defines the initiator/responder roles (offeror and
> >offeree as you say) and is silent on resource provider/consumer roles
> >because these concepts are inherently domain-specific. 
> 
> I don't agree - generally, this is domain-independent precisely because the 
> supplier or provider won't want to commit their goods before they know they 
> are being sold. It also gives them the opportunity to say 'no' in case they 
> have made a mistake or want to offer them to someone else. I say generally, 
> because this may happen but it's a marginal case. Can you give me some 
> examples where the offeror is the supplier/provider?
> 

The very concept of "supplier" and "goods" is necessarily domain
dependent.  Therefore, WS-Agreement cannot make normative statements
about this since it does not actually define any normative terms for
any actual application domain.  That was the general thinking in the
working group after this topic was debated before...


> Also, if "the computing service mak[ing] the offer" is an "unusual 
> scenario", why does the protocol Dominic wrote up from your emails [2] 
> describe this very situation? (Step 5).
> 

Because it was an "unusual" interpretation of what I wrote, i.e. I
would say that this step is completely backwards from what I described
in my email.  Did my reply to Dominic and the graap-wg list not go
through?  I thought I already pointed out that it was backwards, and
repeated the idiomatic advance-reservation solution for 2PC which has
the coordinator acting as initiator to both agreements with the
resource provider.


> >This is something we could have handled in SNAP via our invitation
> >message, but the GRAAP-WG intentionally removed this capability.  As I
> >described in an earlier email, one could approximate this through a
> >sophisticated use of advertisements (templates) and some template
> >exchange system, but I think it is safe to say we marginalized this
> >use case.
> 
> I'm interested to know why this is a marginal use case for GRAAP-WG. I feel 
> it is central in any agreement process in order for both parties to let the 
> other know what they want/are providing without issuing any binding offers.
> 

To illustrate the underlying WS-Agreement model and roles, it is for a
responder to be equipped to receive and consider binding offers, and
to shout from the rooftops: here are my templates, please give me
offers!  And it is for the initiator to somehow (not specified in
WS-Agreement) hear these shouted templates, choose among them,
formulate an offer, and contact the responder to initiate the
protocol.

What was marginalized in WS-Agreement was the idea of a customized or
multi-round advertisement.  It was considered sufficient (for now) to
publish advertisements unilaterally, and formulate offers in response
to these advertisements.

If you want to allow either party to initiate, then the WS-Agreement
solution would be for all parties to publish their templates as
responders, and for all parties to choose wisely when they would like
to become an initiator and make an offer.

If you want custom tailored advertisements that take into account your
own interests, then you need something more sophisticated.  Either an
elaborate brokerage/search facility to locate templates or an explicit
multi-round discovery protocol.  Both of these were set explicitly out
of scope for the first version of WS-Agreement.


> Sorry, but what does "worst opportunity cost" mean? Please, in a couple of 
> sentences :-)
> 
> Michael. 
> 

Well, would we agree with this layman's definition of opportunity
cost: the lost benefit associated with "locking" a resource and taking
it out of play?  If so, then the "worst" one is the one that has a
higher cost in some global value system!

Your judgement about wanting resource providers to be the offeree to
avoid live-lock comes from a global view of the system, where you've
placed value on the opportunity cost for both parties. E.g., if we
stick to the computing environment scenario: the consumer who ties up
his "computational units" and the provider who ties up his
"computation resources". Then, you've made a judgement that the tying
up of resources is a worse outcome than the tying up of the units,
presumably because you expect the resources to be scarce or
utilization to be the most important metric.

This relative evaluation is deeply mired in your assumptions about
what the resources are and what it costs the system (society,
whatever) to have them tied up.  Might there not be a community where
the resource providers are hungry for customers and would gladly act
as offerors to bid for the right to execute their applications?  That
possibility is at the heart of our decision to remain silent and allow
domain-specific profiles of WS-Agreement to choose how best to apply
the protocol.

I personally think that this decision should be allowed at runtime,
because even within a particular application domain, different
participants may have different risk and benefit assessments.  In
fact, these assessments may vary depending on who they are dealing
with.  A fully symmetric deployment of WS-Agreement would allow this.


karl

-- 
Karl Czajkowski
Software Architect

Univa Corporation
1001 Warrenville Road, Suite 550
Lisle, IL 60532

karlcz at univa.com
www.univa.com
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