Using Semantic Web technologies and production rules for reasoning on obligations, permissions, and prohibitions

Nowadays the studies on the formalization, enforcement, and monitoring of policies and norms is crucial in different fields of research and in numerous applications. ODRL 2.2 (Open Digital Right Language) is a W3C standard policy expression language formalized using Semantic Web technologies. It is used to represent permitted and prohibited actions over a certain asset, and obligations required to be met by parties involved in the exchange of a digital asset. In this paper, we propose to extend the model of obligation, permission, and prohibition proposed by ODRL 2.2 in two directions. Firstly, by inserting in the model the notion of activation event (or action) and by expressing event and action as complex constructs having types and application-independent properties. Secondly, by considering the temporal aspects of obligations, permissions, and prohibitions (e.g. expiration dates and deadlines) as part of their application independent model. These extensions are necessary in order to be able to propose an application-independent operational semantics of the extended model, which is formalized using State Machines and is computed by a specific production rule system. The proposed approach has been tested by developing a framework in Java able to get as input a set of policies formalized using Semantic Web languages, and to compute their evolution in time based on the events and actions that happen in the interaction among the parties involved in the specified policies.