Berndt Farwer

A common semantic basis for BDI languages

We describe the design of an intermediate language (AIL) for BDIstyle programming languages. AIL is not intended as yet another programming language, but is meant to provide a common semantic basis for a number of BDI programming languages in order to support both formal verification and the transfer of concepts and developments. We examine some of the key features of AIL, unifying a wide variety of structures appearing in the operational semantics of BDI programming languages. In particular, we highlight issues in the treatment of events, goals, and intentions, which are central to the design of these languages.

A Linear Logic View of Object Petri Nets

Linear Logic [4] has been shown to incorporate a fragment suitable for representing P/T-nets and giving a semantics to the computations of such nets (e.g. [1], [6], [2]). This result is generalised to coloured nets. Furthermore a new kind of high-level nets is defined: Linear Logic Petri Nets (LLPN). These nets are used as an intuitive semantics to well-known and new high-level net concepts like object systems ([8], [12], and [10]) and agent orientation.

Automated Verification of Multi-Agent Programs

In this paper, we show that the flexible model-checking of multi-agent systems, implemented using agent-oriented programming languages, is viable thus paving the way for the construction of verifiably correct applications of autonomous agents and multi-agent systems. Model checking experiments were carried out on AJPF (agent JPF), our extension of Java PathFinder that incorporates the agent infrastructure layer, our unifying framework for agent programming languages. In our approach, properties are specified in a temporal language extended with (shallow) agent-related modalities. The framework then allows the verification of programs written in a variety of agent programming languages, thus removing the need for individual languages to implement their own verification framework. It even allows the verification of multi-agent systems comprised of agents developed in a variety of different (agent) programming languages. As an example, we also provide model checking results for the verification of a multi-agent system implementing a well-known task sharing protocol.

Model checking object petri nets in prolog

Object Petri nets (OPNs) provide a natural and modular method for modelling many real-world systems. We give a structure-pre-serving translation of OPNs to Prolog by encoding the OPN semantics, avoiding the need for an unfolding to a flat Petri net. The translation provides support for reference and value semantics, and even allows different objects to be treated as copyable or non-copyable. The method is developed for OPNs with arbitrary nesting. We then apply logic programming tools to animate, compile and model check OPNs. In particular, we use the partial evaluation system logen to produce an OPN compiler, and we use the model checker xtl to verify CTL formulae. We also use logen to produce special purpose model checkers. We present two case studies, along with experimental results. A comparison of OPN translations to Maude specifications and model checking is given, showing that our approach is roughly twice as fast for larger systems. We also tackle infinite state model checking using the ecce system.

Expressing properties of resource-bounded systems: the logics RTL* and RTL

Computation systems and logics for modelling such systems have been studied to a great extent in the past decades. This paper introduces resources into the models of systems and discusses the Resource-Bounded Tree Logics RTL and RTL*, based on the well-known Computation Tree Logics CTL and CTL*, for reasoning about computations of such systems. We present initial results on the complexity/ decidability of model checking.

Object nets for mobility

This paper studies mobile agents that act in a distributed name space. The difference between belonging to a name space (where objects can be accessed directly via pointers) and migrating between name spaces (where objects have to be treated as values, that can be copied into network messages) is taken account of by introducing Petri net based formalism, employing the nets-within-nets paradigm. This formalism, called mobile object nets, generalises the well-established theory of elementary object nets, which has seen many applications over the last decade. While mobile object nets provide a solution to the specific modelling problem mentioned above, they are much more generic and not restricted to this domain.

A Systematic Approach towards Object-Based Petri Net Formalisms

The paper aims at establishing the semantical background for extending Petri net formalisms with an object-oriented approach by bringing together Nested Petri Nets (NP-nets) of Lomazova and Linear Logic Petri nets (LLPNs) of Farwer. An introductory example shows the capabilities of these formalisms and motivates the proposed inter-encoding of two-level NP-nets and LLPNs. A conservative extension to the Linear Logic calculus of Girard is proposed - Distributed Linear Logic. This extension of Linear Logic gives a natural semantical background for multi-level arbitrary token nets.

Dynamic Modification of System Structures Using LLPNs

In this paper we aim to set up a framework for object Petri net semantics, allowing the modification of object net structures at run-time. The approach uses linear logic Petri nets (LLPNs) and performs the structure modification on a linear logic encoding of the object net. In addition, Valk’s self-modifying Petri nets are shown to be subsumed by LLPNs.

Directions for Agent Model Checking

In this chapter we provide a perspective on current and future work in the area of agent model-checking. In particular, we describe our approach, which was the first to provide comprehensive verification of practical agent programming languages. It provides a library of general agent concepts that has been formally defined and implemented in Java, upon which interpreters for various agent programming languages can be succinctly programmed. The Java library has been prepared so that it can be efficiently used with an existing Java model checker, thus facilitating the verification of (heterogeneous) multi-agent programs. Besides giving an overview of our approach, in this chapter we identify its current shortfalls and discuss where we aim to target future development.

An approach to modelling fms with dynamic object petri nets

AbdmdAnalysis has up to now only been possible for a subclass of static Petri net models for flexible Manufacturing Systems (FMS). In this paper we relax this restriction and introduce the use of (dynamic) object Petri nets for the system model of FMS. By using a eonsemtive extension of the so-far used Petri net formalism we ensure that the crucial deadlock prevention and avoidance algorithms will still b a p plicable. While analysis with respect to deadlock-freeness is maintained, System Engineers gain the possibility of building models that reflect dynamic changes of the formerly static system structure. Furthermore, a clear distinction is made between the models of maehinea, programs, parts, and the deadlock prevention control.