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Subject: RE: [xacml] [Polar] PH09: New section 7.4.2 Attributes

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


-----Original Message-----
From: Seth Proctor [mailto:seth.proctor@sun.com]
Sent: Monday, November 04, 2002 9:59 AM
To: Simon Godik
Cc: xacml@lists.oasis-open.org
Subject: Re: [xacml] [Polar] PH09: New section 7.4.2 Attributes

On Mon, Nov 04, 2002 at 09:39:22AM -0800, Simon Godik wrote:
> use type-one-and-only function:
> apply string-equal
>     apply string-one-and-only
>         subj-attr-desig attrid string-uri issuer must-be-present
>     attr-val string-uri hello

And are you ok with the performance/size overhead this incurs? Nearly every
function in the spec is defined to take single values, which means that
nearly every AD/AS used in a policy will need this wrapping. Also, this
that a function will never know about an empty bag and be able to treat it
differently than an error case, since *-one-and-only is defined to return
Indeterminate if no values are found. When I originally rasised that issue,
TC was adamant that functions should have the ability to differentiate
between an error case and an empty bag.

A second, though much smaller problem, is that it effectively requires
who create new attribute types to create a *-one-and-only function for each
attribute type they invent if they want this behavior. Why not just have
language in the spec that lets a PDP do this implicitly, and save on size,
computation time, complexity, and flexibilty?


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