RE: [xacml] Change request: separating round, abs,floor and othe r function.

On Thu, 22 Aug 2002, Daniel Engovatov wrote:

>
> >to make sure that the result is a singleton. That is inforced by the rule
> >logic, and not by ERROR at the time of evaluation.
>
> I would have to disagree that this is important enough to intriduce
> such additional complexity.

It's actually simpliciticy.

> We agreed that we have to handle errors in evaluation anyway (not just
> invalid sequence length, but invalid syntax, division by zero, or
> whatever else an extension function may require to be communicated as
> "unable to compute" state)

"handle" errors when they are unavoidable, such as divide by zero. It's
another thing to write policies depending on them.

> While we can enforce such limited type safety for standard functions - in
> the way you described
> - it may not be possible to enforce for extension functions.

I don't care about extension functions. Once you've gone beyond the
specified ones, the whole evaluation stragegy is up to you and you can do
what ever you want.

> As we have this mechanism in place - I do not think there is anything
> wrong with using this for checking for correct sequence length - it
> will not affect speed or security in any way.

I don't want people writing policies relying on exceptional ERRORs.

> XACML function can be interpreted INTERNALLY, within implementation,
> to have such length enforcement logic - PAP can deal with that if
> needed.

I'm looking for a formal language that can be verified, typechecked, and
reasoned about. No PDPs, no PAPs, no PEPs. Just language.

> Daniel..
>
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