What's the immutable core of ODRL that cannot be changed by Profiles? #173

4.2 ODRL Profile Requirements

The requirements for communities developing ODRL Profiles MUST document the following:

• Any additions to the Information Model
• Any cardinality changes to the Information Model
• Any aspects of the Information Model that will have different default values or (editorial) interpretations
• Any aspects of the Information Model that is not being supported
• New Vocabulary terms
• Vocabulary terms not explicitly being supported
• Vocabulary terms with more specific interpretations
• The ODRL Profile identifier (IRI)

What are the "core" concepts of ODRL that cannot be changed/removed by Profiles?