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DLN is a recent nonmonotonic description logic, designed for satisfying independently proposed knowledge engineering requirements, and for removing some recurrent drawbacks of traditional nonmonotonic semantics. In this paper we study the logical properties of DLN and illustrate some of the relationships between the KLM postulates and the characteristic features of DLN, including its novel way of dealing with unresolved conflicts between defeasible axioms. Moreover, we fix a problem affecting the original semantics of DLN and accordingly adapt the reduction from DLN inferences to classical inferences. Along the paper, we use various versions of the KLM postulates to deepen the comparison with related work, and illustrate the different tradeoffs between opposite requirements adopted by each approach.

Chapter 1 summarises the results of our structural analysis of the text of the GDPR. The primary goal being to derive a set of must-have structural requirements, that are necessary in order to represent the GDPR in a machine readable format. Chapter 2 in turn details our progress on the the formal representation of the GDPR, which will be iteratively refined throughout the course of the project and completed with the release of the final versions of the pilots’ business policies and GDPR’s formalization (as part of the implementation packages WP3 and WP5).

Policy comparison is useful for a variety of applications, including policy validation and policy-aware service selection. While policy comparison is somewhat natural for policy languages based on description logics, it becomes rather difficult for rule-based policies. When policies have recursive rules, the problem is in general undecidable. Still most policies require some form of recursion to model - say - subject and object hierarchies, and certificate chains. In this paper, we show how policies with recursion can be compared by adapting query optimization techniques developed for the relational algebra. We prove soundness and completeness of our method, discuss the compatibility of the restrictive assumptions we need w.r.t. our reference application scenarios, and report the results of a preliminary set of experiments to prove the practical applicability of our approach.

With the rapid development of various types of open infrastructures, including Internet, grid, and wireless networks, much attention has been focused on the development of distributed systems for collaborative applications in many areas, including collaborative research and development, healthcare, e-commerce, disaster management and homeland security. Besides reliability and timeliness, the great advantages of collaborative distributed systems for improved group awareness and collaboration opportunities are, however, often overshadowed by accompanying security and privacy concerns. In practice, it is desirable that security and privacy for collaborative distributed systems are flexible, scalable and adaptable to the changing and heterogeneous environments. Ensuring efficient collaboration with such security and privacy requirements is a great challenge due to the difficulties of: 1) Ensuring flexible and verifiable security in collaboration. 2) Negotiating and reconciling policies of multiple organizations when the collaboration occurs across organizational boundaries. 3) Collaboratively drawing a conclusion based on data collected from various members while maintaining the privacy of each member. This panel will address various challenging issues of security and privacy in developing collaborative distributed systems and discuss recent advances as well as future trends in dealing with them.