ODRL policy comparison by normalisation

ODRL is a policy-expressing language, framework and vocabulary that has become the standard for representing policies and regulations for digital rights. The complexity of this language is a barrier to its usage, which has caused many related theoretical and practical works to focus on different, and not interoperable, fragments of ODRL. Moreover, semantically equivalent policies can be expressed in numerous different ways, which makes comparing them and processing them harder. Building on top o