Heterogeneous Active Agents

Over the years, many different agent programming languages have been proposed. In this paper, we propose a concept called Agent Programs using which, the way an agent should act in various situations can be declaratively specified by the creator of that agent. Agent Programs may be built on top of arbitrary pieces of software code and may be used to specify what an agent is obliged to do, what an agent may do, and what an agent may not do. In this paper, we define several successively more sophisticated and epistemically satisfying declarative semantics for agent programs, and study the computation price to be paid (in terms of complexity) for such epistemic desiderata. We further show that agent programs cleanly extend well understood semantics for logic programs, and thus are clearly linked to existing results on logic programming and nonmonotonic reasoning. Last, but not least, we have built a simulation of a Supply Chain application in terms of our theory, building on top of commercial software systems such as Microsoft Access and ESRI's Map Object. (Also cross-referenced as UMIACS-TR-98-15

On the Indiscernibility of Individuals in Logic Programming

According to Leibniz' principle, two individuals a and b are indiscernible, if they share the same properties. Indiscernibility of objects provides a potential for optimization in deductive systems, and has e.g. been exploited in the area of active database systems. In this paper, we address the issue of indiscernibility in logic programs and outline possible benefits for computation. After a formal definition of the notion of indiscernibility, we investigate some basic properties. The main contribution is then an analysis of the computational cost of checking indiscernibility of individuals (i.e. constants) in logic programs without function symbols, which we pursue in detail for ground logic programs. For the concern of query optimization, they show that online computation of indiscernibility is expensive, and thus suggest to adopt an offline strategy, which may pay off for certain computational tasks

On the Indiscernibility of Individuals in Logic Programming

According to Leibniz's principle, two individuals a and b are indiscernible, if they share the same properties. Indiscernibility of objects provides a potential for optimization in deductive systems, and has e.g. been exploited in the area of active database systems. In this paper, we address the issue of indiscernibility in logic programs and outline possible benefits for computation. After a formal definition of the notion of indiscernibility, we investigate some basic properties. The main contribution is then an analysis of the computational cost of checking indiscernibility of individuals (i.e. constants) in logic programs without function symbols, which we pursue in detail for ground logic programs. For the concern of query optimization, they show that online computation of indiscernibility is expensive, and thus suggest to adopt an offline strategy, which may pay off for certain computational tasks