Title: Interaction and Interference: Two-Party Contracts
joint work with Fernando Schapachnik (Universidad de Buenos Aires)

Disclaimer: This talk is not about ACTA.

Abstract: Deontic logic has long been used to describe the ideal (as opposed to actual) behaviour of entities, allowing for the formalisation of notions such as permission and obligation. The advantage of looking at such statements from a deontic logic perspective, as opposed to as a set of properties, is that the clauses become first class objects in a logic about which we can reason directly. Furthermore, concepts such as violation and consequences of violation can be reasoned about within the logic. This is becoming more and more important in, for instance, web-service contract negotiation, and service-composition (where each of the services comes with a contract). Many questions arise: Are two contracts compatible? Is a contract stronger than another? Of the different deontic modalities, the concept of a right is particularly interesting. Unlike others such as obligation and prohibition which are violated when an entity achieves (or fails to achieve) a goal, a right is violated when the option to achieve that goal is not available.  A crucial question addresses the meaning of having the option to do something. Who grants or denies it? Much work appears in the literature formalising and studying the  different types of rights. The problem is that frequently one has to formalise ancillary notions such as intention, causality and interference. However, computer scientists have long studied interacting two-party systems in the form of synchronous systems - which give many if not all of the desired notions. In this talk I will be discussing recent work with Fernando Schapachnik in which we explored the use of synchronous composition as a basis for deontic semantics for two party systems. In particular, I will be discussing different types or rights in such a setting, and compare them to existing approaches in the literature.