Their Problems Are My Problems -- The Transition between Internal and External Conflict

In Multi-Agent Systems there has been quite an amount of research on how to model conflicts in (intelligent) agent architectures for example by imitating mental states and augmenting them with social notions. Nevertheless, a great deal of investigation is missing on the transition between internal and external conflicts. Arguments in favor of taking a closer look at this transition include a practical one from applications where internal conflicts may easily become external conflicts and vice versa, and a technical one motivated by the existence of more efficient algorithms for solving internal conflicts. In tji

From Formal Workflow Models to Intelligent Agents

Todays business workflows, e.g. in administration, have a strong need for support by information technology, because they heavily rely on the efficient and fluent interaction of human actors and artificial systems. At the same time, workflow tasks supported or automatically executed by computers get more and more complex. Intelligent agents try to cope with both of these settings by providing a Software Engineering abstraction, which incorporates complex functionality for task planning and execution with elaborate interaction capabilities. This paper presents a method for identifying and specifying such agents and their behavior by careful analysis of formal workflow models. It follows a small example out of an industrial-size case study, which is currently conducted at Europe's biggest hospital, Charit'e Berlin. There are at least two aspects of todays business workflows, which have to be considered for support by information technology. The first aspect is the partially or fully aut..

A Formalization of Autonomous Dynamic Reconfiguration in Distributed Constraint Satisfaction

Several interesting practical problems in process control, planning and scheduling can be expressed and solved using the model of constraint satisfaction problems. At least four drawbacks of this classical model directly relate to areas of distribution: complexity, scalability, privacy and robustness. Hence, research on distributed constraint satisfaction problems is a new direction in the area of multi-agent systems. A typical engineering task in distributed constraint satisfaction is the design of the distribution itself. A careful look at this task reveals that the design of distribution is critical to the quality and efficiency of the problem solving process and is itself an optimization problem

On Proving Properties of Concurrent Algorithms for Distributed CSPs

Because of social, economical and technical reasons, some years ago the classical CSP model has been extended to the model of Distributed Constraint Satisfaction Problems (DCSPs) in which several computational agents try to solve a connected CSP collectively. Many recent systems tackling this problem lack a theoretically founded specification and safety or liveness property proofs. This may be due to the difficulty of modeling and verifying concurrently running threads and their interaction. In this article we will briefly present a general approach to the modeling and verification of concurrent algorithms tailored to DCSP solving and based on algebraic Petri nets. We will present a realistic case study on distributed agreement finding and prove according termination and consistency properties. 1. INTRODUCTION The model of Constraint Satisfaction Problems (CSPs) and its according methods in information propagation and search have proven to be well-suited to solve common practical pro..

B-DIce - A BDI Control Environment for Manufacturing Systems

B-DIce is a Belief-Desire-Intention control environment for Flexible Manufacturing Systems. It is a Multi Agent System and consists of agents of medium complexity. The target of this project is to create a system, which reliably and efficiently deals with dynamic job shop scheduling problems. At the same time, solutions presented by the system shall be comprehensible for the human planner. This article provides an overview on the progress of this project, including the formal problem specification, design of the agents and their interactions. 1 Introduction The development and maintenance of complex systems, like manufacturing control systems, is only practicable with the help of sophisticated software techniques. Until today, Object Oriented Techniques are the choice of industry. Recently it is discussed, whether the notion of autonomous "agents" could be helpful for structuring complex heterogeneous systems. Agents allow a level of data abstraction, which cannot be achieved by tradi..

Autonome Dynamische Rekonfiguration im kooperativen Problemlösungsprozeß

Mit dieser Arbeit wird eine ausführliche Untersuchung von kooperativem Problemlösen, seinen Vor- und Nachteilen, vor allem aber seiner Verbesserung durch Autonome Dynamische Rekonfiguration vorgelegt. Autonome Dynamische Rekonfiguration behandelt zwei typische Probleme kooperativen Problemlösens: schlechte Problemlösungsergebnisse und hoher Kommunikationsaufwand. Die Kernidee ist dabei die autonome und dynamische Anpassung der Konfiguration eines Problemlösungsprozesses, d. h. der Verteilung von Wissen, Zielen und Fähigkeiten, an das Problem selbst. Grundlage dafür sind zwei lokale Operationen: Agent Melting und Agent Splitting. Beim Agent Melting werden das Wissen, die Ziele und Fähigkeiten mehrerer Agenten in einem Agenten zusammengeführt, beim Agent Splitting ein Agent in mehrere Agenten zerlegt, wobei möglicherweise neue Agenten entstehen. Dabei wird eine stichhaltige theoretische Grundlage sowohl für kooperatives Problemlösen als auch für Autonome Dynamische Rekonfiguration gelegt. Die Problemstellung, eine gute Konfiguration für ein gegebenes Problem zu finden, weist eine Verbandsstruktur auf und ist nachweislich schwer zu lösen. Durch die Charakterisierung von Agent Melting und Agent Splitting als Operationen auf Äquivalenzrelationen können wichtige Eigenschaften dieser Operationen nachgewiesen werden, wie Strukturerhalt, Wirkung, Hinlänglichkeit und nebenläufiges Verhalten. Im praktischen Teil dieser Arbeit wird eine effiziente und effektive Instanz von kooperativem Problemlösen präsentiert. Alle dargestellten Konzepte, wie das Multi-phase-Agreement-Finding-Protokoll zum externen Problemlösen, die kompositionale Belief-Desire-Intention-Agentenarchitektur und eine spezielle Architektur zur Constraint-Spezifikation beim internen Problemlösen, sind so entworfen, daß sie mit dynamischen Konfigurationsänderungen umgehen können. Alle Konzepte werden durch einen lokalen Steuerungsmechanismus integriert, der durch Beobachtung und Selbstbeobachtung entscheidet, wie die Konfiguration angepaßt werden muß. Sowohl Theorie als auch Praxis werden mithilfe einer Fallstudie aus der medizinischen Terminplanung evaluiert. Die Autonome Dynamische Rekonfiguration liefert dabei überzeugende Ergebnisse - die Lösungsqualität wird um bis zu 20 Prozent gesteigert, während der Kommunikationsaufwand mehr als halbiert wird. Mithilfe dieser Technik erreicht der kooperative Problemlösungsprozeß fast die Qualität eines zentralen Ansatzes, ist aber effizienter.This thesis is a comprehensive study of collaborative problem solving, its advantages and pitfalls, but mainly its improvement by autonomous dynamic reconfiguration. Autonomous dynamic reconfiguration deals with two common problems in collaborative problem solving - poor problem solving results and high communication effort. The main idea of autonomous dynamic reconfiguration is to autonomously and dynamically adapt the configuration of a collaborative problem solving effort, i.e. the distribution of knowledge, goals and skills, to the problem itself. This is done by two individual local operations -- agent melting and agent splitting. Agent melting means to unify the knowledge, goals and skills of two or more agents in a single agent, while agent splitting denotes a process in which a single agent is split, possibly resulting in an additional new agent. In this work we lay a sound theoretical foundation for collaborative problem solving itself and for its improvement by autonomous dynamic reconfiguration. The problem of finding a good configuration for a given problem has been proven to feature a lattice structure and to be complex to solve. Based on a characterization of agent melting and agent splitting as equivalence relation manipulators, these two operators show verifiable properties regarding structure retainment, impact, sufficiency and concurrency. On the practical side, collaborative problem solving finds a very flexible and effective instantiation in this work. All presented concepts for collaborative problem solving, such as the multi-phase agreement finding protocol for external problem solving, the composable belief-desire-intention agent achitecture and the distribution-aware constraint specification architecture for internal problem solving, are designed to support a changing configuration. This set of concepts is integrated by the AuReCon controller that decides by observation and self-observation how to locally adjust the configuration. The proposed theory and practice are validated using a case study in medical appointment scheduling. The autonomous dynamic reconfiguration approach shows convincing results in improving the problem solving quality by up to 20 percent and by more than halving the communication effort. Using autonomous dynamic reconfiguration, the collaborative problem solving techniques can match the quality of a central approach and are more efficient

Distributed Constraint Optimization for Medical Appointment Scheduling

Though multi-agent systems seem to be promising to solve scheduling problems in administration and health care management, most implemented recent systems lack a sound foundation for collaboration. Research in distributed constraint satisfaction/optimization problems (DCSPs and DCOPs) could yield a change here. But instead of tackling academic-size problems with complete algorithms, in this paper we present an approach to coordinate several agents each using an o-the-shelf constraint solver in a real-world case study. We present a full DCOP model of medical appointment scheduling as well as inter-agent and intra-agent algorithms to solve this problem

Coordinating distributed CLP-solvers in medical appointment scheduling

Abstract. Research on monolithic logic-based systems has usually left out an important aspect of information technology systems supporting medical processes — distribution. Often social restrictions build up by questions of authority prohibit the implementation of global systems with omniscient view. Hence, IT in medical domains has to obey these restrictions by being distributed as well. The direct consequence is the need for communication and coordination. In this paper, we present an industrial-size case study in medical appointment scheduling that is envisaged to be solved by combining the strength of CLP for local (internal) problems with the strength of coordination for external problems. The essence of this approach is the realization of a multi agent system (MAS) consisting of CLP-based agents.

Transforming Object-Oriented Domain Models into Declarative CLP Expressions

An increasing number of applications of information technology is characterized by the need for sophisticated methods of knowledge-based problem solving. Hence, though most of the recent software systems are written in traditional programming languages there has been increasing awareness of the demand for more abstract and declarative languages. In this paper, we will present a multi-stage framework for transforming object-oriented domain models, as they can often be found in information systems, into more declarative constraint logic expressions to solve complex problems. This framework is tailored to the needs of distributed constraint satisfaction among several agents. We will exemplify the usage of our concepts by following a real-world case study in medical appointment scheduling. 1 Introduction An increasing number of industrial and administrative applications of information technology is characterized by the need for sophisticated methods of problem solving, such as ..