Subject: RE: On policy conditions

From: "David Allan" <[email-masked]>
Date: Wed, 21 Apr 1999 08:15:17 -0500

I need to rephrase a bit of this....

Unless we are defining the ability for the PDP/PEP pair to spontaneously
create information as a result of policy and internal stimulus (as in the
backup example), then the only time that policy and instrumentation needs to
be examined is coincident with a packet arrival. It is the unit of work. All
transitions of any consequence originate with the arrival of a unit of work.
The instrumentation needs to be able to classify the content of the unit of
work, extract meaning, modify state and decide if a policy rule requires
examination. Of course, by that definition it becomes reasonable to suggest
that the only things that are policy inputs are transitions as the
instrumentation decided there was a reason to examine a rule as a result of
some change. (of course the implementation COULD constantly poll everything,
but WHY????). My nomenclature suggests that transitions occur in the support
infrastructure and provide reason to examine specific policy rules (the
policy triggers are pushed into the stateful side of the system). 

What concerns me is the suggestion that policy decide when work should be
performed (as in the backup example) rather than the dispostion of work.
That to me is starting to boil the ocean a bit.

Dave

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From: Changpeng Fan <[email-masked]>
Date: Thu, 22 Apr 1999 09:00:21 +0200

> My nomenclature suggests that transitions occur in the support

I can agree with this as an alternative conceptual interpretation.
Actually, what I mean by "meta-rule control" is something similar:
Some meta-rules are available to control which rules or rule
sets should currently be active. In the case of a state transition
triggered by time, water mark or emergency, a meta-rule may
instruct the decision engine to switch from one rule set into
another or to activate/deactivate chosen rules. State thrashing
is surely a concern here. But anyhow it would be convenient
to be able to use event triggers as part of the input conditions
to these meta-rules.

-- Changpeng