Handle Multiple Users/Subjects

Hi,

I’m researching about Multi User Authorisation and decided to work on a prototype with XACML.

In the Core Spec there is a paragraph about Multiple Subjects. But if I get it right it’s more about multiple Subjects in terms of one Access-Subject which uses a Programm (as another subject) to access resource X.

In my reserach I consider the scenario where Bob and Alice are both on one system and want to access a resource.
I have several ideas how to realise this but I’m not sure if I miss a fundamental point in XACML.

Is it supported that two access-subjects request one resource in a single request?

Best regards,

Arno