Logic Fragments: Coordinating Entities with Logic Programs

Abstract

Rigorous engineering of self-organising and self-adaptive systems is a challenging activity. Interactions with humans and unexpected entities, dependence on contextual information for self-organisation and adaptation represent just some of the factors complicating the coordination process among multiple entities of the system. Recently we proposed a coordination model based on logic inference named Logic Fragments Coordination Model. Logic Fragments are combinations of logic programs defining interactions among agents distributed over the nodes of the system. They are able to accommodate various types of logics, ranging from classical up to many-valued paraconsistent ones. The logical formalisation makes it possible to express coordination in a rigorous and predicle way, both at design-time and run-time. In this paper we define, under the form of an evaluation algorithm, the semantics of Logic Fragments; introducing logical predicates used to manage and reason on local and remote information. By associating specific semantics to the symbols inferred during the evaluation of logic programs it is possible to make logical inference effects unambiguous on the system; such an approach turns Logic Fragments into a coordination-oriented logic-based programming model. We conclude the paper discussing three examples showing the use of Logic Fragments to implement on-the-fly ad-hoc coordination mechanisms, as well as design-time and run-time verification of spatial properties.