Subject: Core Model Last Call Issue: Execution Semantics

From: [email-masked]
Date: Wed, 12 Apr 2000 12:54:48 -0400

Allow me to renew my objection to the fact that the core information
model execution semantics are inherently ambiguous, and hence will lead
to implementations that make different policy decisions when given
identical policies and inputs.  This objection has been raised before,
and has been "featurized" rather than addressed in the core info model
draft via the following text in Section 2.2:

2. An important decision to make is the semantic style of the
      representation of the information.

      The declarative approach that we are describing falls short of
      being a "true" declarative model. Such a model would also specify
      the algorithms used to combine the information and policy rules to
      achieve particular behavior. We avoid specifying algorithms for the
      same reason that we avoid specifying sets of steps to be followed
      in a policy rule. However, the design of the information model more
      closely follows that of a declarative language, and may be easier
      to understand if such a conceptual model is used. This leads to our
      third point, acknowledging a lack of "completeness" and instead
      relying on presenting information that the policy processing entity
      will work with.

"presenting information that the policy processing entity will work with"
implies that different entities will work with it in different ways.
This will not lead to interoperation among those entities in a fashion
that implements a single policy in a consistent fashion.  IMHO, this
needs to be corrected here, rather than patched over in the policies
derived from this model, such as the QoS policy.

--David

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David L. Black, Senior Technologist
EMC Corporation, 42 South St., Hopkinton, MA  01748
+1 (508) 435-1000 x75140, FAX: +1 (508) 497-6909
[email-masked]  Cellular: +1 (978) 394-7754
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From: "John Strassner" <[email-masked]>
Date: Wed, 12 Apr 2000 13:22:11 -0700

Hi David,

I'm curious why you didn't mention this during our first
last call. At some point, we need to go with the consensus,
which is quite happy with the declarative approach.

I also think that you need to explicitly state why you think
that the "execution semantics are inherently ambiguous, and
hence will lead to implementations that make different
policy decisions when given identical policies and inputs".
I would like an example, because I don't understand your

> implies that different entities will work with it in
different ways.

This is not implied at all. What is stated is that the
design of the information model will present the information
in a standard form. Your statement is someone specious,
since even if I prescribed all of the steps of an algorithm,
a processing entity could still decide that it needed to
pre- or post-process those results, or even insert
additional steps. I think that one could successfully argue
that any of these three alternatives would result in a
"divergent" implementation. That is exactly why we tried to
avoid specifying all of the nitty gritty detail - it is
impossible to cover all uses of a generic policy model by
over-definition.

> derived from this model, such as the QoS policy.

I don't follow at all. What do you mean by "patched" in the
QoS policy model?

So please, come up with some real, concrete examples as to
why this model is broken, or at least suggest some
clarifying wording.

regards,
John

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From: Su <[email-masked]>
Date: Thu, 13 Apr 2000 20:32:16 +0800 (SST)

Hello all.

I am new to this list. If I am asking this question in the wrong forum,
kindly correct me.

After having read through RFC2748, 2749 and 2750, I still don't
understand a few things.

1. Does COPS define how administrative domains are to be represented? 

I don't believe that client-handle is unique for a unique socket. For
example, if in an organisation, there were three admin-domain viz.
top-management, admin and tech-staff... then, the same socket can be
used by people from different domains. And since they are from different
domains, the policies pertaining to each of them should be different
(intuitively speaking).

How does the current COPS version handle this? How can I specify a
client-handle?

2. Is Client-SI fully and comprehensively defined?

Thank you for taking the time to read this newbie question. 

Cheers!
--Su.

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Sujatha Natraj				National University of Singapore
Undergraduate, year 3			Dept. of Computer Engineering

	SMTP    :[email-masked]
	HTTP	:http://www.comp.nus.edu.sg/~sujathan 
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