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1. Applying the ATAM to an Architecture for Decentralized Control of a Transportation System

Author

Boucké, Nelis, Weyns, Danny, Schelfthout, Kurt, Holvoet, Tom, Hutchison, David, editor, Kanade, Takeo, editor, Kittler, Josef, editor, Kleinberg, Jon M., editor, Mattern, Friedemann, editor, Mitchell, John C., editor, Naor, Moni, editor, Nierstrasz, Oscar, editor, Pandu Rangan, C., editor, Steffen, Bernhard, editor, Sudan, Madhu, editor, Terzopoulos, Demetri, editor, Tygar, Dough, editor, Vardi, Moshe Y., editor, Weikum, Gerhard, editor, Hofmeister, Christine, editor, Crnkovic, Ivica, editor, and Reussner, Ralf, editor

Published
2006
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2. Views: Middleware Abstractions for Context-Aware Applications in MANETs

Author

Schelfthout, Kurt, Holvoet, Tom, Berbers, Yolande, Hutchison, David, Series editor, Kanade, Takeo, Series editor, Kittler, Josef, Series editor, Kleinberg, Jon M., Series editor, Mattern, Friedemann, Series editor, Mitchell, John C., Series editor, Naor, Moni, Series editor, Nierstrasz, Oscar, Series editor, Pandu Rangan, C., Series editor, Steffen, Bernhard, Series editor, Sudan, Madhu, Series editor, Terzopoulos, Demetri, Series editor, Tygar, Dough, Series editor, Vardi, Moshe Y., Series editor, Weikum, Gerhard, Series editor, Garcia, Alessandro, editor, Choren, Ricardo, editor, Lucena, Carlos, editor, Giorgini, Paolo, editor, Holvoet, Tom, editor, and Romanovsky, Alexander, editor

Published
2006
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3. Exploiting a Virtual Environment in a Real-World Application

Author

Weyns, Danny, Schelfthout, Kurt, Holvoet, Tom, Hutchison, David, Series editor, Kanade, Takeo, Series editor, Kittler, Josef, Series editor, Kleinberg, Jon M., Series editor, Mattern, Friedemann, Series editor, Mitchell, John C., Series editor, Naor, Moni, Series editor, Nierstrasz, Oscar, Series editor, Pandu Rangan, C., Series editor, Steffen, Bernhard, Series editor, Sudan, Madhu, Series editor, Terzopoulos, Demetri, Series editor, Tygar, Dough, Series editor, Vardi, Moshe Y., Series editor, Weikum, Gerhard, Series editor, Carbonell, Jaime G., editor, Siekmann, Jörg, editor, Weyns, Danny, editor, Van Dyke Parunak, H., editor, and Michel, Fabien, editor

Published
2006
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4. Towards Adaptive Role Selection for Behavior-Based Agents

Author

Weyns, Danny, Schelfthout, Kurt, Holvoet, Tom, Glorieux, Olivier, Hutchison, David, editor, Kanade, Takeo, editor, Kittler, Josef, editor, Kleinberg, Jon M., editor, Mattern, Friedemann, editor, Mitchell, John C., editor, Naor, Moni, editor, Nierstrasz, Oscar, editor, Pandu Rangan, C., editor, Steffen, Bernhard, editor, Sudan, Madhu, editor, Terzopoulos, Demetri, editor, Tygar, Dough, editor, Vardi, Moshe Y., editor, Weikum, Gerhard, editor, Carbonell, Jaime G., editor, Siekmann, Jörg, editor, Kudenko, Daniel, editor, Kazakov, Dimitar, editor, and Alonso, Eduardo, editor

Published
2005
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5. Architecture-Centric Development of an AGV Transportation System

Author

Weyns, Danny, Schelfthout, Kurt, Holvoet, Tom, Hutchison, David, editor, Kanade, Takeo, editor, Kittler, Josef, editor, Kleinberg, Jon M., editor, Mattern, Friedemann, editor, Mitchell, John C., editor, Naor, Moni, editor, Nierstrasz, Oscar, editor, Pandu Rangan, C., editor, Steffen, Bernhard, editor, Sudan, Madhu, editor, Terzopoulos, Demetri, editor, Tygar, Dough, editor, Vardi, Moshe Y., editor, Weikum, Gerhard, editor, Carbonell, Jaime G., editor, Siekmann, Jörg, editor, Pěchouček, Michael, editor, Petta, Paolo, editor, and Varga, László Zsolt, editor

Published
2005
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7. A Basic Taxonomy for Role Composition

Author

Steegmans, Elke, Schelfthout, Kurt, Holvoet, Tom, Berbers, Yolande, Valckenaers, Paul, Germain, Bart Saint, Goos, Gerhard, editor, Hartmanis, Juris, editor, van Leeuwen, Jan, editor, Lucena, Carlos, editor, Garcia, Alessandro, editor, Romanovsky, Alexander, editor, Castro, Jaelson, editor, and Alencar, Paulo S. C., editor

Published
2004
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15. A Basic Taxonomy for Role Composition

Author

Steegmans, Elke, primary, Schelfthout, Kurt, additional, Holvoet, Tom, additional, Berbers, Yolande, additional, Valckenaers, Paul, additional, and Germain, Bart Saint, additional

Published
2004
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16. Adding variants on-the-fly: Modeling meta-variability in dynamic software product lines

Author

Helleboogh, Alexander, Weyns, Danny, Schmid, Klaus, Holvoet, Tom, Schelfthout, Kurt, and Van Betsbrugge, Wim

Abstract

Dynamic software product lines (DSPL) are software product lines (SPL) that support runtime variability. Runtime variability is typically interpreted as binding variation points at runtime. We emphasize meta-variability as an important dimension of runtime variability in DSPL. Whereas dynamic binding considers the runtime (de)activation of variants within the scope of a given variability model, meta-variability considers runtime changes to the variability model itself. Meta-variability is essential to support long-lived software products that are subject to evolution. In this paper, we consider meta-variability in an industrial DSPL that is developed in a joint project with Egemin N.V., a leading company that provides full life cycle support for automated transportation systems (ATS). The contribution of this paper is threefold. First, we introduce a way to model meta-variability in DSPL in an explicit manner. Second, we put forward a meta-variability meta model that extends the variability meta model with concepts that explicitly support meta-variability. Third, we capture and apply meta- variability in an industrial DSPL for automated transportation systems. ispartof: pages:18-27 ispartof: Proceedings of the Third International Workshop on Dynamic Software Product Lines (DSPL @ SPLC 2009) pages:18-27 ispartof: Third International Workshop on Dynamic Software Product Lines: DSPL 2009 location:Pittsburgh, PA, USA date:24 Aug - 24 Aug 2009 status: published

Published
2009

17. Towards of software product line for automated transportation systems

Author

Weyns, Danny, Helleboogh, Alexander, Holvoet, Tom, Schelfthout, Kurt, and Van Betsbrugge, Wim

Abstract

ispartof: pages:105-118 ispartof: Proceedings of the Second International Workshop on Dynamic Software Product Lines pages:105-118 ispartof: Dynamic Software Product Lines location:Limerick, Ireland date:8 Sep - 8 Sep 2008 status: published

Published
2008

18. Supporting Coordination in Mobile Networks: a Middleware Approach (Ondersteuning van coördinatie in mobiele netwerken door middel van een middleware platform) : Supporting Coordination in Mobile Networks: a Middleware Approach

Author

Schelfthout, Kurt, Berbers, Yolande, and Holvoet, Tom

Abstract

Draadloze communicatie en de steeds groter wordende miniaturisering van computerapparaten, verhoogt de ontwikkeling en het gebruik van zogenaamde mobiele software toepassingen. Mobiele toepassingen voeren uit op knopen die zelf kunnen bewegen, terwijl ze draadloos verbonden blijven met het netwerk. Mobiele toepassingen worden gekenmerkt door (1) hun noodzaak om rekening te houden met hun fysische omgeving, typisch context genoemd; (2) hun noodzaak om om te gaan met dynamiek en onverwachte gebeurtenissen uit hun context. Deze thesis stelt ten eerste twee rogrammeerabstracties voor, views en rollen, die het ontwerpen en implementeren van mobiele toepassingen vergemakkelijken door tegemoet te komen aan de twee bovenstaande noden. Ten tweede, worden twee alternatieve implementatiestrategieën voor een middleware platform dat beide abstracties ondersteunt, voorgesteld en geëvalueerd. Ten derde wordt de bruikbaarheid van beide abstracties nagegaan in een industriële toepassing. De eerste abstractie, een view, is een automatisch onderhouden verzameling van data objecten, die kopieën of representaties zijn van data objecten verkregen van een aantal knopen in het netwerk. De middleware automatiseert het verzamelen van de data objecten van de knopen, en onderhoudt het view terwijl de data objecten en knopen continu veranderen. De tweede abstractie, een rol, bevat het gedrag van een component van de toepassing die deelneemt aan de uitvoering van een protocol. De middleware automatiseert het starten en onderhouden van een sessie van het protocol uitgevoerd tussen een aantal componenten, terwijl de deelnemers aan het protocol omwille van hun mobiliteit continu wijzigen. Twee implementatie strategieën voor een middleware platform ter ondersteuning van beide abstracties worden voorgesteld, respectievelijk voor mobiele en voor mobiele ad hoc netwerken. Beide strategieën worden analytisch en empirisch gevalideerd, om het effect van (soms oncontroleerbare) parameters na te gaan op bandbreedte-verbruik en betrouwbaarheid. De validatie toont aan dat beide implementaties praktisch bruikbaar zijn. De bruikbaarheid van de abstracties wordt nagegaan door ze toe te passen in een controle toepassing voor onbemande voertuigen. De voertuigen moeten automatisch ladingen verplaatsen in een magazijn of fabriek. Uitdagende problemen zoals vermijden van botsingen, vermijden van deadlock, en toewijzen van taken worden met behulp van het middleware platform opgelost. Dit levert sterke aanwijzingen op dat de abstracties en middleware het ontwikkelen van mobiele applicaties vereenvoudigen en versnellen. 1 Introduction 1 1.1 Background . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 1.2 Problem . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 1.3 Approach . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 1.4 Contributions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 1.5 Overview of the Text . . . . . . . . . . . . . . . . . . . . . . . . . 9 2 Background 11 2.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 2.2 Communication Mechanisms for Coordination in Distributed Applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 2.3 Modularising Coordination . . . . . . . . . . . . . . . . . . . . . 20 2.4 Scope of the Thesis . . . . . . . . . . . . . . . . . . . . . . . . . . 26 2.5 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31 3 Objectplaces 33 3.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33 3.2 Concepts and Definitions . . . . . . . . . . . . . . . . . . . . . . 34 3.3 Basic Operations . . . . . . . . . . . . . . . . . . . . . . . . . . . 35 3.4 Composed Operations . . . . . . . . . . . . . . . . . . . . . . . . 40 3.5 Example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43 3.6 Related Work . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44 3.7 Summary and Conclusion . . . . . . . . . . . . . . . . . . . . . . 44 4 Views 45 4.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45 4.2 Concepts and Definitions . . . . . . . . . . . . . . . . . . . . . . 48 4.3 Gathering and Maintaining View Content . . . . . . . . . . . . . 50 4.4 Constructing View Representations . . . . . . . . . . . . . . . . . 53 4.5 Object-Oriented Interface . . . . . . . . . . . . . . . . . . . . . . 54 4.6 Quality of Views . . . . . . . . . . . . . . . . . . . . . . . . . . . 56 4.7 Example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57 4.8 Related Work . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58 4.9 Summary and Conclusion . . . . . . . . . . . . . . . . . . . . . . 61 5 Roles 63 5.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63 5.2 Concepts and Definitions . . . . . . . . . . . . . . . . . . . . . . 66 5.3 Support for Interaction Session Setup and Maintenance . . . . . 69 5.4 Support for Design of a Role’s Behaviour . . . . . . . . . . . . . 78 5.5 Example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81 5.6 Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87 5.7 Related Work . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 90 5.8 Summary and Conclusion . . . . . . . . . . . . . . . . . . . . . . 92 6 Architecture and Implementation 93 6.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 93 6.2 Architecture . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 94 6.3 Group Formation Implementation for Mobile Networks . . . . . . 102 6.4 Group Formation Implementation for Mobile Ad Hoc Networks . 105 6.5 Other Implementation Options . . . . . . . . . . . . . . . . . . . 126 6.6 Related Work . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 127 6.7 Summary and Conclusions . . . . . . . . . . . . . . . . . . . . . . 130 7 Application and Validation in AGV Control 131 7.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 131 7.2 AGV Control Application . . . . . . . . . . . . . . . . . . . . . . 132 7.3 Collision Avoidance . . . . . . . . . . . . . . . . . . . . . . . . . 139 7.4 Deadlock Avoidance . . . . . . . . . . . . . . . . . . . . . . . . . 154 7.5 Transport Assignment using Gradient Fields . . . . . . . . . . . . 162 7.6 Summary and Conclusion . . . . . . . . . . . . . . . . . . . . . . 167 8 Conclusions 169 8.1 Contributions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 170 8.2 Open Problems and Future Work . . . . . . . . . . . . . . . . . . 172 A Collision Avoidance Protocol 191 A.1 Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 191 A.2 Invariant . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 192 A.3 Maintaining the Invariant . . . . . . . . . . . . . . . . . . . . . . 193 B Deadlock Prevention 197 B.1 Step 1: Building a wait-for graph . . . . . . . . . . . . . . . . . . 197 B.2 Step 2: Construction of deadlock zones . . . . . . . . . . . . . . . 198 B.3 Step 3: Preventing deadlock using zones . . . . . . . . . . . . . . 199 B.4 Ordering of the Nodes in a Zone . . . . . . . . . . . . . . . . . . 200 B.5 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 201 nrpages: 201+viii status: published

Published
2006

19. Views: customizable abstraction for context-aware applications in MANETs

Author

Schelfthout, Kurt, Holvoet, Tom, Berbers, Yolande, Garcia, A, Choren, R, Lucena, C, Romanovsky, A, Holvoet, Tom, and Giorgini, P

Abstract

ispartof: pages:39-46 ispartof: Proceedings of Software Engineering for Large Scale Multi-Agent Systems 2005 pages:39-46 ispartof: Software Engineering for Large Scale Multi-Agent Systems location:St. Louis, Missouri, USA date:15 May - 16 May 2005 status: published

Published
2005

20. ObjectPlaces: an environment for situated multi-agent systems

Author

Schelfthout, Kurt and Holvoet, Tom

Abstract

Situated multi-agent systems are MAS with an explicit representation of the environment, which agents can observe and in which agents can act. An appropriate middleware platform should support the construction and manipulation of such an environment. We require three properties from the environment: (1) observableness: an agent must be able to get a current view on its context; (2) activity: the environment updates the agent's current view; (3) dynamism: the environment can change without direct influence from the agents. ObjectPlaces is a tuplespace-like middleware that offers an event-based interface and a concept of dynamic objects to support these requirements. ispartof: pages:1500-1501 ispartof: Proceedings of the Third International Joint Conference on Autonomous Agents and Multiagent Systems, AAMAS 2004 vol:3 pages:1500-1501 ispartof: Autonomous Agents and Multi-Agent Systems location:New York date:19 Jul - 23 Jul 2004 status: published

Published
2004

21. Decentralized Control of Automatic Guided Vehicles : applying multi-agent systems in practice

Author

Weyns, Danny, Holvoet, Tom, Schelfthout, Kurt, Wielemans, Jan, Weyns, Danny, Holvoet, Tom, Schelfthout, Kurt, and Wielemans, Jan

Abstract

An automatic guided vehicle (AGV) transportation system is a fully automated system that provides logistic services in an industrial environment such as a warehouse or a factory. Traditionally, the AGVs that execute the transportation tasks are controlled by a central server via wireless communication. In a joint effort between Egemin, an industrial manufacturer of AGV transportation systems, and DistriNet Labs research at the Katholieke Universiteit Leuven, we developed an innovative decentralized architecture for controlling AGVs. The driving motivations behind decentralizing the control of AGVs were new and future quality requirements such as flexibility and openness. At the software architectural level, the AGV control system is structured as a multi-agent system; the detailed design and implementation is object-oriented. In this paper, we report our experiences with developing the agent-based control system for AGVs. Starting from system requirements, we give an overview of the software architecture and we zoom in on a number of concrete functionalities. We reflect on our experiences and report lessons learned from applying multi-agent systems for real-world AGV control.

Published
2008
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22. Towards a software product line for automated transportation systems

Author

Weyns, Danny, Helleboogh, Alexander, Holvoet, Tom, Schelfthout, Kurt, Van Betsbrugge, Wim, Weyns, Danny, Helleboogh, Alexander, Holvoet, Tom, Schelfthout, Kurt, and Van Betsbrugge, Wim

Abstract

Since the seventies, Egemin has successfully been providingfull life cycle support for automated transportation systems(ATS) used to automate internal logistics in productionand warehousing environments. With increasing customerdemands a number of considerable problems related to thecompany’s engineering practice came to the surface. Examplesare duplication of solutions and erosion of the softwareand its architecture. With the introduction of a softwareproduct line (SPL) Egemin aims to shift the focus ofits activities from developing individual products (ATS forclients) towards the development of a repository of core assetsfor a family of ATS supported by an explicitly definedproduction process. The objective is to establish plannedreuse aiming to improve the quality of the software and ultimatelyto increase productivity. A particular challenge withthe introduction of the SPL is support for runtime variabilitythat allows an ATS to dynamically adapt its behavior tochanges in the operating environment. In this paper, we outlinehow Egemin is introducing a dynamic SPL for ATS. Wegive particular attention to support for runtime variability.

Published
2008

24. Multiagent systems as software architecture : another perspective on software engineering with multiagent systems

Author

Weyns, Danny, Holvoet, Tom, Schelfthout, Kurt, Weyns, Danny, Holvoet, Tom, and Schelfthout, Kurt

Abstract

The trend in agent-oriented software engineering is to consider multiagent systems (MASs) as a radically new way of engineering software. This position isolates agent-oriented software engineering from mainstream software engineering and could be one important reason why MASs are not widely adopted in industry yet.In this paper, we present another perspective on software engineering with MASs. We put forward MASs as software architecture. We give an overview of a reference architecture for situated MAS. This reference architecture extracts and generalizes common functions and structures from various applications we have studied and built. The reference architecture provides a blueprint for architectural design of MAS applications that share the come base of the systems it is derived from. Considering MASs essentially as software architecture paves the way to integration with mainstream software engineering.

Published
2006
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25. DynCNET : a protocol for flexible task assignment applied in an AGV transportation system

Author

Weyns, Danny, Boucké, Nelis, Schelfthout, Kurt, Holvoet, Tom, Weyns, Danny, Boucké, Nelis, Schelfthout, Kurt, and Holvoet, Tom

Abstract

The work presented in this paper is part of an ongoing effort to study suitable task assignment mechanismsfor decentralized MAS. Our focus is on systems that are characterized by tasks with delayedcommencement. Such a task requires a preceding effort before the agent can start executing the task. Anexample is a robot that first has to move to the location of a task before it can start executing that task.Important quality requirements for assigning tasks with delayed commencement are flexibility (enableagents to adapt task assignment with changing circumstances) and openness (enable agents to take intoaccount other agents that come and go during the process of task assignment).In previous work, we have studied Contract Net (CNET) and a field-based approach for task assignment(FiTA). CNET does not provide the required flexibility and openness. FiTA satisfies the requiredqualities, however, the field-based approach provides an emergent solution for task assignment. It is wellknown that emergent solutions are difficult to engineer and reason about. This raises the question whetherit is not easier to extend CNET to take dynamics and changes into account.This paper presents the DynCNET protocol. DynCNET is an extention of CNET, with “Dyn” referringto support for dynamic task assignment. DynCNET provides flexibility and openness for assigningtasks with delayed commencement. We compare the DynCNET protocol with CNET and FiTA in anAGV transportation system. Our experiences in this real-world setting show that: (1) the performance ofDynCNET and FiTA are similar, while both outperform CNET; (2) extending CNET to deal with delayedcommencement of tasks is not obvious; the complexity to engineer DynCNET is similar to FiTA but muchmore complex than CNET; (3) whereas task assignment with FiTA is an emergent solution, DynCNETexplicitly specifies the interaction among agents allowing engineers to reason on the assignment of tasks.This latter property may be of overriding importance

Published
2006

26. Decentralized control of E'GV transportation systems

Author

Weyns, Danny, Schelfthout, Kurt, Holvoet, Tom, Lefever, Tom, Weyns, Danny, Schelfthout, Kurt, Holvoet, Tom, and Lefever, Tom

Abstract

Egemin N. V. is a Belgian manufacturer of Automatic Guided Vehicles -named E'GVs- and control software for automating logistics services in warehouses and manufactories using E'GVs. In a joint R&D project, Egemin and the AgentWise research group are developing an innovative version of the E'GVs control system aimed to cope with new and future system requirements such as flexibility and openness.In this project, we exploit principles and mechanisms known from situated multi-agent systems for modelling and implementing a decentralized control system. Instead of a centralistic approach, where one computer system is in charge of numerous complex and time-consuming tasks (such as routing, collision avoidance, deadlock avoidance, etc.), we aim to provide the E'GVs with a considerable amount of autonomy. This allows to obtain a system that is far more flexible than the current software - the E'GVs adapt themselves to the current situation in their direct vicinity, order assignment is dynamic, the system can cope with E'GVs leaving the system (e.g. for maintenance) or adding new E'GVs, and so on.In this paper, we describe the architecture that is employed for implementing the control of the E'GV system. The implementation of the control software seamlessly integrates with E'nsor, the low-level vehicle control system. We illustrate a concrete control scenario in which two E'GVs coordinate their behavior to avoid collisions.

Published
2005
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27. Middleware for protocol-based coordination in dynamic networks

Author

Schelfthout, Kurt, Weyns, Danny, Holvoet, Tom, Schelfthout, Kurt, Weyns, Danny, and Holvoet, Tom

Abstract

Pervasive and ad hoc computing applications are frequently deployed in dynamic networks. Due to mobility of the computing nodes, their unreliability, or a limited communication range, at any time a node may enter or leave an interaction between a group of application components. Middleware approaches have been proposed to deal with these dynamics, by supporting the dissemination (or gathering) of information in dynamic networks. In our experience however, applications frequently need to execute a complete protocol to coordinate. Existing middleware can then be used as a discovery mechanism, but offers no support for handling the protocol itself. This paper presents a middleware model that enables an easier implementation of distributed protocols that need to take into account the continuously changing context in the dynamic network. It uses roles as a first order abstraction, handles the distributed instantiation of roles in an interaction session, and maintains the session as nodes in the mobile network move. We describe our experience with applying the middleware in a case study on a system of automatic guided vehicles.

Published
2005
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28. Agent implementation patterns

Author

Schelfthout, Kurt, Coninx, Tim, Helleboogh, Alexander, Holvoet, Tom, Steegmans, Elke, Weyns, Danny, Schelfthout, Kurt, Coninx, Tim, Helleboogh, Alexander, Holvoet, Tom, Steegmans, Elke, and Weyns, Danny

Abstract

Our own experience in developing agents and multi-agent systems painfully taught us that there are no instruments to support the implementation of such systems. A thorough literature study confirms the fact that implementation issues, which are definitely non-trivial but clearly underestimated, are mostly achieved in an ad hoc fashion. This obviously results in people reinventing solutions for common problems. In this paper, we propose agent implementation patterns as an instrument to describe problems and generic solutions for implementing agents and multi-agent systems. Agent implementation patterns contrast with other proposals of agent patterns in that the latter typically deal with architectural and conceptual models, and not with the actual implementation of agent characteristics. If we eventually want to come to a best practice for the development and implementation of agent systems, system developers should share their knowledge and experience gained during the implementation of their systems. Agent implementation patterns can contribute to formalize and share such knowledge.

Published
2002

34. Views

Author

Schelfthout, Kurt, primary, Holvoet, Tom, additional, and Berbers, Yolande, additional

Published
2005
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36. Exploiting a Virtual Environment in a Real-World Application.

Author

Van Dyke Parunak, H., Michel, Fabien, Weyns, Danny, Schelfthout, Kurt, and Holvoet, Tom

Abstract

In situated multi-agent systems (situated MASs), agents are explicitly placed in an environment. A situated agent does not not use long-term planning to decide what action sequence should be executed, but selects actions on the basis of its current position, the world it perceives and limited internal state. Situated agents exploit the environment to coordinate their behavior and to reach a common goal. In a recent project, we applied situated MASs to the control of an automated transportation system that uses automatic guided vehicles (AGVs) to transport loads in a warehouse. In contrast to traditional approaches where the AGVs are controlled by a central server, in this project we model the AGVs as agents in a situated MAS, aiming to improve flexibility and openness. Since the physical environment of AGVs is very restricted, it offers little opportunities for agents to use the environment. We introduce a virtual environment for agents to live in. This virtual environment (1) offers a medium that agents can use to exchange information and coordinate their behavior, and (2) serves as a suitable abstraction to shield low-level physical processing from the AGV agents. Since the only infrastructure available to the AGVs is a wireless network, the virtual environment is necessarily distributed over the AGVs. Synchronization of the state of the virtual environment is provided by ObjectPlaces, a middleware infrastructure that offers support to exchange and share information among nodes in mobile and ad-hoc networks. In this paper, we demonstrate how the environment is used creatively in the design of a MAS solution, helping to manage the complexity of engineering a complex real-world application. [ABSTRACT FROM AUTHOR]

Published
2006
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37. Views: Middleware Abstractions for Context-Aware Applications in MANETs.

Author

Garcia, Alessandro, Choren, Ricardo, Lucena, Carlos, Giorgini, Paolo, Romanovsky, Alexander, Schelfthout, Kurt, Holvoet, Tom, and Berbers, Yolande

Abstract

Programming applications for highly dynamic environments such as mobile ad hoc networks (MANETs) is complex, since the working context of applications changes continuously. This paper presents "views" as abstractions for representing and maintaining context information, tailored to applications in MANETs. An application agent can define a view by declaratively describing the context information it is interested in. A supporting middleware platform, called ObjectPlaces, ensures that the information represented by a view continuously reflects the agent's context information, despite the dynamic situation in a MANET. We elaborate on the distributed protocol that ObjectPlaces uses to maintain the information of views, and give an evaluation of the protocol's correctness and overhead. [ABSTRACT FROM AUTHOR]

Published
2006
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40. Views.

Author

Schelfthout, Kurt, Holvoet, Tom, and Berbers, Yolande

Published
2005
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41. Architecture-Centric Development of an AGV Transportation System.

Author

Pěchouček, Michael, Petta, Paolo, Varga, László Zsolt, Weyns, Danny, Schelfthout, Kurt, and Holvoet, Tom

Abstract

Architectural design plays a key role in software engineering. The software architecture is the backbone of the designed solution, it has the functional requirements of the system and satisfies the quality requirements. In our research, we put forward situated multiagent systems (situated MAS) as an approach to build distributed applications with demanding quality requirements such as flexibility and openness. In this paper we illustrate how we apply situated MAS to an Automatic Guided Vehicle (AGV) transportation system. We discuss the high-level structure of the software architecture and explain how the architecture aims to meet important quality requirements. [ABSTRACT FROM AUTHOR]

Published
2005
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42. Towards Adaptive Role Selection for Behavior-Based Agents.

Author

Kudenko, Daniel, Kazakov, Dimitar, Alonso, Eduardo, Weyns, Danny, Schelfthout, Kurt, Holvoet, Tom, and Glorieux, Olivier

Abstract

This paper presents a model for adaptive agents. The model describes the behavior of an agent as a graph of roles, in short a behavior graph. Links between roles provide conditions that determine whether the agent can switch roles. The behavior graph is assigned at design time, however adaptive role selection takes place at runtime. Adaptivity is achieved through factors in the links of the behavior graph. A factor models a property of the agent or its perceived environment. When an agent can switch roles via different links, the factors determine the role the agent will switch to. By analyzing the effects of its performed actions the agent is able to adjust the value of specific factors, adapting the selection of roles in line with the changing circumstances. Models for adaptive agents typically describe how an agent dynamically selects a behavior (or action) based on the calculation of a probability value as a function of the observed state for each individual behavior (or action). In contrast, the model we propose aims to dynamically adapt logical relations between different behaviors (called roles here) in order to dynamically form paths of behaviors (i.e. sequences of roles) that are suitable in the current state. To verify the model we applied it to the Packet-World. In the paper we discuss simulation results that show how the model enables the agents in the Packet-World to adapt their behavior to changes in the environment. [ABSTRACT FROM AUTHOR]

Published
2005

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