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

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

> My suggestion was to treat Designator used as an argument for a funciton
> requiring single attribute as if it is implicitly wrapped in *-one-and-only
> function application (will yield indeterminate if the bag is not of size
> one)

Actually, it can be even simpler. Regardless of where the Designator/Selector
is, let return either a bag with one element or just that element when it
only resolves one value. If this is in a function, that function will decide
what to do if it gets a bag with multiple values (ie, it might be able to
handle it, it might be indeterminate, it might be able to skip it and try
other resoltions).

If you require a designator/selector to act in a special way when it's inside
a function, you muddy the logic of the AD/AS, and if you tell it to always
act as a *-one-and-only you break functions that can deal with (or expect to
get) bags, since there is no way to know that a certain parameter to a certain
function does/doesn't want a bag.

Were you ok with the one sentence addition proposed? Ie

  "A bag containing one value is treated as semantically equivalent to a
   single value of the specified bag type."


seth


ps  In general, I think what you've suggested also makes sense, but I'd need
to see some specific text to make sure.