Re: [xacml] XACML Issues List Version 01

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2002-01-10T07:14:00+00:00
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Re: [xacml] XACML Issues List Version 01
Hi
> I believe Periangela's list was missing one issue from Tim, so that will
> have to be added in.

yes, i was missing a proposal by Tim with respect to issue
[PM-1-02: Post-conditions]. I included it in by changing the description
of the issue in my copy while on the concall monday as reported below.
could you pls substitute the paragraph below to the current one?
thx.

best
-p

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* post-condition. The current schema [Tim, Jan.3] mentions

post-conditions, distinguishing between external and internal,

depending on whether their execution requires dialoging with

external entities. The current schema suggests (via a comment)

that post-conditions can be expressed as invocations of SOAP

services. Post-conditions are still to be discussed in details:

what is their semantics; how are they executed? A complication of

post-conditions associated with a rule involves the distributed

scenario (see POLICY COMPOSITION issue). In fact, if I say that a

post-condition should be applied whenever a rule fires then I have

to evaluate *all* rules. A possible way to overcome this problem

is to consider that post-conditions associated with the

authorizations that were evaluated to get to an access decision

should be executed [Tim]. Note: a possible drawback of this

approach is that deterministic behavior may be lost. For instance,

there may be N rules applying to an access. If the evaluation of 1

of them brings to a ``permit'' decision (so there is no need to

evaluate the others). Then, you would ignore the postconditions

possibly associated with the other N-1. Different execution of the

same request on the same state could then have a different

behavior (because a different rule is considered as authorizing

the request.

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