[xacml] Present Elements

[Polar Humenn <polar@syr.edu>]

Everybody,

Given that I am writing up sections for the following elements:

SubjectAttributeIsPresent
SubjectAttributeIsPresentWhere
ResourceAttributeIsPresent
ActionAttributeIsPresent
EnvironmentAttributeIsPresent
SelectedAttributeIsPresent

These elements will basically extend the AttributeDesignatorType and will
have meanings as booleans.

So, these structures return a value of type "xs:boolean". The question is
do we include the "mustBePresent" attribute of which Simon is presently
placing in the AttributeDesignatorType. It may be useful to some (I
wouldn't use it), but it could be.

Let's say we have the following:

<ActionAttributeIsPresent AttributeId="urn:....:action-id"/>

would return TRUE if the attribute is present, and would return FALSE if
it were not. There could be operational errors that may cause it to return
Indeterminate, but presence is not one of them.

Now let's say for discussion, what if we have:

<ActionAttributeIsPresent
      AttributeId="urn:....:action-id"
      MustBePresent="true"/A>

I would suggest that this structure return TRUE if the attribute is not
there, and raise and Indeterminate, if not.

It's not that I would use it, but I'm just thinking of completeness here.
Being that

<ActionAttributeDesignator
     AttributeId="urn:...:action-id"/>

may return values or an empty bag, and

<ActionAttributeDesignator
     AttributeId="urn:...:action-id"
     MustBePresent="true"/>

may return values or Indeterminate.  (I guess it will return an empty bag
if it is present and has no value?)

What do people think?

-Polar