Re: [xacml] New issue#1 from "Boolean Policy resolution"

[Polar Humenn <polar@syr.edu>]

On Fri, 8 Feb 2002, bill parducci wrote:

> >>...which in the context of granting access is the functional equivalent
> >>of setting N/A = TRUE.
> >>
> >>t + n/a = t
> >>
> >
> > Not so, the semantics is that the policy does not apply.
> > We are working with a 3 valued logic (4 if we include evaulation error).
> >
> > f or n/a = f,  (i.e. n/a is not "set" to "true").
> >
>
>
> help me understand this, evaluating the following using this logic
>
>
> t AND n/a
>
> is reduced to
>
> t
>
> which evaluates to TRUE. therefore,
>
> t AND n/a = t
>
> bottom line: if 'n/a' means 'do not consider when resolving' it
> evalutates to TRUE when used in an AND clause in terms of *functional*
> equivalency. can you give me an exmaple otherwise?

In the proposed logic,

t AND t = t
t AND n/a = t

However, that does NOT mean that for

t AND x = t

x must be t (in this logic). For an analogous example in classical logic,
Take implication =>

t => t = t
t => f = f
f => t = t
f => f = t

x => t = t does not force x to be t
f => x = t does not force x to be t.

n/a is n/a. It is a separate entity.

cheers,
-Polar

>
> b
>
>
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