Re: [xacml] [Polar] PH09: New section 7.4.2 Attributes

[Seth Proctor <seth.proctor@sun.com>]

On Mon, Nov 04, 2002 at 10:05:27AM -0800, Daniel Engovatov wrote:
> There is exactly the same performance overhead to perform this check 
> whatever the semantics of this expression is.  Somewhere, somehow you will
> have if(size == 1) expression evaluated.

Actually, no. It's much more than just a simple if(size == 1) check that
we're talking about, since there's an extra Apply, an extra function
evaluation, an extra etc...not to mention the extra bits on disk to store
a policy with all that extra stuff in it. Using the one-and-only functions
results in a much more expensive evaluation all around.

> Implicit application, as I suggested, will allow the implementation to
> optimize it a bit though - to avoid an extra value copy probably..

If the way this mapping is done is through an explicit use of the one-and-only
functions, you cannot do an implicit application of this functionality and
still produce an interoperable PDP. Ie, it will treat the same policy data
differently in some cases than other PDPs. This is Bad. Either the spec is
explicit about a way to treat these values implicitly, or the one-and-only
functions are used, which is expensive. It does much more than just "avoid
an extra value copy"


seth