Nowadays economy is every day more and more a digital economy where many human activities are performed by means of digital devices on digital assets. It is useless that digital assets are made public without the specification of constrains on their usage and access, this because the absence of a license or an agreement on the use of the data is not equivalent to the right to do whatever a person wants with those data. Licenses and agreements may be specified using human-readable formats, but the increasing usage and exchange of digital assets requires more formal and machine-readable mechanisms for their specification. This in order to enable machine to machine interactions combined with a number of useful services, like: (i) an advance search of resources based on their license; (ii) the possibility to aggregate different resources released under different licenses by computing license compatibility or conflicts; (iii) the automatic checking of the satisfaction or violations of the normative or legal relations that such an exchange of digital assets may create in the chain of interactions among data producers, data publishers, and data consumers.
In order to perform many of those services it is crucial to propose not only the syntax of a formal language for expressing licenses, norms, and agreements, but for being able to perform automatic reasoning on those “constrains” it is also fundamental to express a formal semantics of such a language. Among the existing formal languages for expressing licenses or more general normative or legal relations among autonomous parties/agents (norms and agreements), the most interesting one is ODRL. Therefore, the first objective of this project proposal is to investigate how it is possible to extend the expressivity of ODRL for being mainly able to express: (i) pure obligations and the relationships among obligations, permissions, and prohibitions and their temporal dynamics; (ii) institutional power to create and modify policies on digital assets; (iii) introducing temporal aspects. Another limit of ODRL is that it has only an informal semantics. Without a formal semantics it is not possible to perform automatic reasoning on those policies and therefore it is quite impossible to automatically provide monitoring and simulation services. Therefore, the second goal of this project is to specify the semantic aspects of the proposed extended normative language. The third goal is to design, develop, and evaluate a software framework able to exploit automatic reasoning on the semantics of norms for providing the fundamental services described above.
Our approach will mainly consists in proposing the extension of the ORDL language by expressing the semantics of the new concepts and their dynamics in a semiformal but rigorous way, by complementing formal models with informal specifications in natural language. Then, we will investigate two possible approaches for the formal specification of the semantics of the proposed language based as much as possible on the adoption of Semantic Web Technologies. We shall then choose the solution that, while being sufficiently expressive, has the best performance in spite of a growing amount of data on the protected digital assets and number of high-level norms and norm instances. The performances will be evaluated by implementing the various components of the software framework able to provide the services of monitoring, simulation, and norms consistency check. The framework scalability will be evaluated by measuring the complexity of the algorithms proposed and by comparing its performances with other approaches presented in literature.