Category declarations

Attribute category declarations offer short names for attribute categories, making them readily usable in attribute declarations. Typically you don't need to declare your own categories since system.alfa declares the four standard attribute categories, as follows:

category subjectCat  = "urn:oasis:names:tc:xacml:1.0:subject-category:access-subject"
category resourceCat = "urn:oasis:names:tc:xacml:3.0:attribute-category:resource"
category actionCat = "urn:oasis:names:tc:xacml:3.0:attribute-category:action"
category environmentCat = "urn:oasis:names:tc:xacml:3.0:attribute-category:environment"