[xacml] questions about section 5 and is-present elemets

I'm incorporating Polar's text into section 
5.

 

I have couple of questions:

1. is it nesessary to call 
subject-attribute-designator 
categorized-subject-attribute-designator

since we do not have -where element any 
more?

 

2. for is present designators:

is'n it better do define 'present' function that 
takes as an argument existing attribute deisgnators:

<Apply FunctionId="present">

    <ResourceAttributeDesignator 
... />
</Apply>

 

Simon