Bilattices, due to M. Ginsberg, are a family of truth value spaces that allow elegantly for missing or conflicting information. The simplest example is Belnap's four-valued logic, based on classical two-valued logic. Among other examples are those based on finite many-valued logics, and on probabilistic valued logic. A fixed point semantics is developed for logic programming, allowing any bilattice as the space of truth values. The mathematics is little more complex than in the classical two-valued setting, but the result provides a natural semantics for distributed logic programs, including those involving confidence factors. The classical two-valued and the Kripke/Kleene three-valued semantics become special cases, since the logics involved are natural sublogics of Belnap's logic, the logic given by the simplest bilattice. 1 Introduction Often useful information is spread over a number of sites ("Does anybody know, did Willie wear a hat when he left this morning?") that can be speci...

Abstract—Component-based software engineering is generally recognized as one of the best methods to develop, deploy, and manage increasingly complex software systems. To enable the dynamic composition of software modules, it is often required to expose their functionality dependencies. This results the a well-known requires-provides specifications ’ model. In this paper, we introduce a framework that enables individual software components to specify their requires-provides interfaces in a policy dependent way. Our framework specifies policies as combinations of Constraint Logic Programming (CLP) based rules. Moreover, our policies are flexible and expressive, allowing the enforcement of multiple aspects for the requested composition including security and quality of service. We apply our framework to specify Quality of Protection (QoP) and Quality of Service (QoS) policies. We demonstrate the applicability of our policy language using as an example a teleconferencing application with diverse requirements for the specification of security and resource policies. Keywords-Policy-based software composition; Policies for software interfaces; Policies for aspect-oriented software I.