1. N.I. Karacapilidis, D. Papadias, T. Gordon and H. Voss, Collaborative Environmental Planning with GeoMed, European Journal of Operational Research, Special Issue on Environmental Planning, to appear.

   Environmental planning usually involves a large number of decision makers with different backgrounds and interests. Appropriate decision making procedures are needed in order to jointly consider their individual approaches and achieve collaboration. This paper discusses issues involved in Collaborative Environmental Planning and reports work on GeoMed, a group decision support system for Geographical Mediation on the World Wide Web. We first present an argumentation framework that constitutes the core of the system and supports fair, rational and efficient decision making. In the sequel, we discuss the necessary enhancements in order to deal with spatial applications, and environmental planning in particular. Finally, we give a description of GeoMed and an overview of the services provided.

2. N.I. Karacapilidis and C.P. Pappis, A framework for Group Decision Support Systems: Combining AI tools and OR techniques, European Journal of Operational Research, Special Issue on AI tools for Decision Support Systems, to appear.

   Work on the implementation of Group Decision Support Systems has to exploit recent advancements of computer science. Existing frameworks for single-user Decision Support Systems, based on well-established Operations Research methods such as Multicriteria Decision Making techniques, have to be integrated with successful technical developments in electronic communication and computing. Starting from the presentation of the related Operations Research background, this paper proceeds by discussing challenges coming from the areas of Computer-Supported Cooperative Work and Information Systems on the World Wide Web platform. Based on this discussion, a framework for an "open", computer-mediated Group Decision Support System is proposed. The term "open" is related to a platform-independent system, which can efficiently support alternative types of goals and control protocols between its users.

3. N.I. Karacapilidis and C.P. Pappis, Production Planning and Control in Textile Industry: A case study, Computers in Industry, Vol. 30, 1996, pp. 127-144.

   This paper presents an interactive model based system for the management of production in textile production systems focusing on the Master Production Scheduling problem. Because of the special characteristics of the industry, that is mainly the multi-phase process with multiple units per phase, different planning horizons and different production requirements for each phase, the scheduling of these systems becomes quite complex. Apart from a comprehensive presentation of the set of the modules the system is composed of, together with their interrelationships, the above characteristics are analyzed, and their impact on the production control system is explained. The system is also related to two well-known production control systems, namely MRP-II and Optimised Production Technology. The system's attributes are presented with the aid of data structure diagrams, while the complete algorithm concerning the Master Production Scheduling module, in a pseudo-code form, and the corresponding part of the database are illustrated in the Appendix.

4. N.I. Karacapilidis, C.P. Pappis and G.I. Adamopoulos, On a World Wide Web based Planning Support System, YUJOR, Vol. 6, No 2, 1996, pp. 159-169. Also in Proceedings of the 3rd Balkan Conference on Operational Research, Thessaloniki, Greece, October 16-19, 1995.

   Work presented in this paper focuses on the design of a computer-mediated system for supporting group planning on the World Wide Web platform. It is shown that, by developing a suite of appropriate intelligent tools and providing a public-domain application, any Web browser, such as Mosaic or Netscape, may be sufficient for an agent to take part in a planning procedure. The specific role of the system is that of an assistant and advisor, recommending solutions and leaving the final decisions and actions to the agents. In other words, it emphasizes on a human-human coordination, communication and problem solving, rather than on a human-machine one. The proposed framework decomposes the problem of group planning into decision-making, uncertainty handling, constraint satisfaction and propagation, and integrates them appropriately.

5. N.I. Karacapilidis and C.P. Pappis, Form Similarities of the CON and SLK Due Date Determination Methods, Journal of Operational Research Society, Vol. 46, 1995, pp. 762-770.

   The optimal due date determination and sequencing problem of n jobs, on a single machine, with deterministic processing times is reviewed. An algorithm, using the SLK method, has been previously described by the authors, by means of which one optimal sequence as well as all the alternative optima are determined without resorting to the Complementary Pair and Exchange Principle concepts. In this paper, a similar algorithm using the CON method is proposed, the optimization criterion being the minimization of the total lateness penalty. It is shown that both algorithms lead to the same minimum value of the objective function. It is also shown that all the alternative optima of either method may be determined if those derived from the other are known.

6. C.P. Pappis and N.I. Karacapilidis, Lot size scheduling using fuzzy numbers, International Transactions in Operational Research, Vol. 2, No 2, 1995, pp. 205-212.

   Due to imprecision that is often inherent in the estimates of future demand for various products in a batch type production system, there are cases where the lot sizing problem may be more naturally treated using fuzzy concepts. Triangular fuzzy sets may be employed in order to represent qualitative estimates that are expressed linguistically. In this paper the above approach is introduced in order to derive an appropriate number of production runs and the corresponding lot sizes.

7. N.I. Karacapilidis and C.P. Pappis, Optimization algorithms for a class of single machine scheduling problems using due date determination methods, YUJOR, Vol. 5, No 2, 1995, pp. 289-297.

   The problem of determining optimal schedules for the static, single machine scheduling problem with the aid of CON and SLK due date determination methods is considered. The objective is to minimize the total weighted earliness and tardiness penalty in the case which weights are proportional to the processing times of the respective jobs. For each method, an optimization algorithm has been developed, by means of which the set of all optimal sequences is provided. The numerical example, presented after the theoretical foundation, confirms considerations about the structural similarity of the two methods.

8. C.P. Pappis and N.I. Karacapilidis, Application of a similarity measure of fuzzy sets to fuzzy relational equations, Fuzzy Sets and Systems, Special Issue on Fuzzy Relation - Part 2, Vol. 75, No 2, 1995, pp. 135-142.

   In this paper, the grade of similarity of two fuzzy sets A and B is defined and its properties are given. The set G(R,b) of grades of similarity associated with the set of the solutions of the Inverse Problem ("given a fuzzy matrix R and a fuzzy vector b find all a such that a R = b") is also defined and several properties are shown.

9. C.P. Pappis and N.I. Karacapilidis, Applying the service level criterion in a location allocation problem, Decision Support Systems, Vol. 11, 1994, pp. 77-81.

   A DSS to help solve the location-allocation problem applying service level criterion is presented in this paper. The decisive parameters considered are the maximum allowable distance between a customer and the respective supplying center and the total number of such centers. A case study of a Greek bottling company with computational results is also included.

10. N.I. Karacapilidis and C.P. Pappis, Optimal Due Date Determination and Sequencing of n Jobs on a Single Machine Using the SLK Method, Computers in Industry, Vol. 21, 1993, pp. 335-339.

    The problem of scheduling n jobs with deterministic processing times on a single machine is considered. An algorithm, by means of which the set of all optimal sequences is obtained using the SLK due date assignment method, is provided. The optimization criterion used is the minimization of the total earliness and tardiness penalty. It is proven that this set can be determined without making use of the Complementary Pair and Exchange Principle concepts.

11. C.P. Pappis and N.I. Karacapilidis, A comparative assessment of measures of similarity of fuzzy values, Fuzzy Sets and Systems, Vol. 56, No 2, 1993, pp. 171-174.

    The properties of several measures of similarity of fuzzy values are presented and compared. The measures examined include the measure based on the union and intersection, the one based on the maximum difference and the one based on the differences as well as the sum of the corresponding grades of membership. It is shown that several properties are common to all measures. However, some properties do not hold for all of them.

12. G. Adamopoulos, N.I. Karacapilidis, and S.N. Pantazopoulos, Production management in the textile industry using the YFADI decision support system, Computers and Chemical Engineering, Vol. 18 Suppl., 1994, pp. 577-583. Also in Proceedings of ESCAPE-3/European Symposium on Computer Aided Process Engineering, Graz, Austria, July 5-7, 1993.

    The decision support system (DSS) presented here is dealing with the production planning and scheduling in the textile industry. The DSS aims at the efficient management of a mixed production system (job-shop and flow-shop), such as that of the textile industry. Its main feature is the effective combination of a database and a model based management system in order to merge existing expert knowledge. A powerfull user interface makes the DSS user-friendly. A multi-module formulation is used for better interpretation and analysis of the production procedures.

Conference Papers (refereed on the full paper)

1. N.I. Karacapilidis and D. Papadias, A Group Decision and Negotiation Support System for Argumentation Based Reasoning, in Gr. Antoniou & M. Truszczynski (eds) Learning and Reasoning with Complex Representations, Springer-Verlag, Berlin, Lecture Notes in AI, to appear.

   This paper describes a Group Decision and Negotiation Support System for cooperative or non-cooperative argumentative discourses. The system provides agents means of expressing and weighing their individual arguments and preferences, the aim being the selection of a certain choice. It also supports defeasible and qualitative reasoning in the presence of ill-structured information. Argumentation is performed through a set of discourse acts which call a variety of procedures for the propagation of information in the corresponding discussion graph.

2. N.I. Karacapilidis, B. Trousse and D. Papadias, Using Case-Based Reasoning for Argumentation with Multiple Viewpoints, in Proceedings of the 2nd International Conference on Case-Based Reasoning (ICCBR'97), Providence, Rhode Island, July 25-27, 1997, Springer-Verlag, Berlin, Lecture Notes in AI, to appear.

   The integration of classical case-based reasoning with other problem solving methods attracts increasing research interest in the broader area of information and decision support systems. This paper presents a framework where CBR and Argumentation Based Reasoning jointly aid agents to address various discourse instances in group decision making processes. The ability to comprehend and engage in arguments is essential for these environments, while use of precedent cases is well-suited. Cases in our model are not merely considered as representations of past data, but as flexible entities associated with the underlying viewpoint of an agent and the evolution of the corresponding discussion. The paper provides an object-oriented description of the elements involved, and illustrates their dependencies through a comprehensive example.

3. T. Gordon and N.I. Karacapilidis, The Zeno Argumentation Framework, in Proceedings of the 6th International Conference on Artificial Intelligence & Law (ICAIL'97), Melbourne, Australia, June 30 - July 3, 1997, to appear. Also in Proceedings of the Workshop on Computational Dialectics: Models of Argumentation, Negotiation and Decision Making, International Conference on Formal and Applied Practical Reasoning (FAPR'96), Bonn, Germany, June 3-7, 1996.

   The Zeno Argumentation Framework is a formal model of argumentation based on the informal models of Toulmin and Rittel. Its main feature is a labelling function using arguments to compute heuristic information about the relative quality of the alternative positions proposed as solutions for some practical issue. The Zeno Argumentation Framework was designed to be used in mediation systems, an advanced kind of electronic discussion forum with special support for argumentation, negotiation and other structured forms of group decision-making.

4. N.I. Karacapilidis, D. Papadias and T. Gordon, An Argumentation Based Framework for Defeasible and Qualitative Reasoning, in D.L. Borges and C.A.A. Kaestner (eds.) Advances in Artificial Intelligence, Proceedings of the XIIIth Brazilian Symposium on Artificial Intelligence (SBIAÕ96), Curitiba, Brazil, October 23-25, 1996, Springer-Verlag, Berlin, Lecture Notes in AI, Vol. 1159, 1996, pp. 1-10. Also in Proceedings of the ECAI'96 Workshop on Gaps and Bridges: New Directions in Planning and Natural Language Generation, Budapest, Hungary, August 12-16, 1996, pp. 37-42.

   Multiagent settings are usually characterized by numerous goals, diverse opinions and conflicts of interest. In order to reach understanding and achieve cooperation, agents need a means of expressing their individual arguments which may contain explanations, justifications or any other kind of information. Furthermore, existing information may usually be incomplete, inconsistent and expressed in qualitative terms. In this paper, we present an argumentation-based framework that supports defeasible and qualitative reasoning in such environments. An interval-based qualitative value logic is applied, together with an inference mechanism in order to refine agents' knowledge, check consistency and, eventually, conclude the issue. The model is currently under development in Java, the aim being to deploy it on the World Wide Web.

5. T. Gordon, N.I. Karacapilidis, H. Voss and A. Zauke, Computer-Mediated Cooperative Spatial Planning, Proceedings of the 3rd International Conference on Design and Decision Support Systems in Architecture and Urban Planning, Vol. 2, Spa, Belgium, August 18-21, 1996, pp. 105-116.

   Decision making on spatial planning problems has to integrate recent advancements on geographical information systems with a framework that supports fair, rational and efficient decision making procedures. Such a framework will assist government and businesses with the retrieval, use and reuse of information in cooperative, distributed planning procedures requiring access to spatial data. This paper gives an overview of a computer-mediated group decision support system for the World Wide Web, namely ZENO. The target is to provide intelligent assistance to human mediators and other kinds of "trusted third parties" during the above procedures. The role of the system is to remain neutral and help assure that the interests and goals of all members of a group, regardless of their status, are respected and appreciated. In this paper, the system's features are illustrated with a retrospective model of a real urban planning example, concerning the allocation of a new technology park in the area of the city of Bonn, where more than eighty communities, local and federal authorities, and other organizations have been requested to submit their suggestions, objections and comments on a spatial planning problem.

6. N.I. Karacapilidis, T. Gordon, D. Papadias and H. Voss, Building an Interactive Multimedia Information System: The GeoMed case study, Proceedings of the ECAI'96 Workshop on Knowledge Representation for Interactive Multimedia Systems: Research and Experience (KRIMS'96), Budapest, Hungary, August 12-16, 1996, pp. 10-16.

   Implementation of information systems has witnessed a movement towards data types of increasing complexity. This is widely facilitated by recent advances in computing and communication. At the same time, the user community does not only need access to existing information in various systems, but efficient ways to contribute its own. This paper discusses issues on the development of an Interactive Multimedia Information System on the World-Wide Web. Reporting work on GeoMed, a new EU-funded project aiming at building a Geographical Mediation System, we indicate means of indexing, organization and management of information. Multimedia information is represented in GeoMed within electronic documents and messages, not only as passive data but as graphical user interfaces to external Information Systems. Concepts discussed include Multimedia Information Management Systems, semantics, annotation tools, knowledge representation structures and reasoning mechanisms.

7. T. Gordon, N.I. Karacapilidis and H. Voss, ZENO - A Mediation System for Spatial Planning, in U. Busbach, D. Kerr and K. Sikkel (eds.) CSCW and the Web - Proceedings of the 5th ERCIM/W4G Workshop, Sankt Augustin, Germany, February 7-9, 1996, Arbeitspapiere der GMD 984, pp. 55-61.

   Zeno is a mediation system for the World-Wide Web. It allows large numbers of interested parties in various locations to take part in a planning process over an extended period of time. In the paper, we introduce our context of application, i.e. city and regional planning, and then derive some very general requirements for an adequate information technology support for participants in such planning processes. Our Zeno system, designed to meet these requirements, is introduced next. The further development of Zeno will take place as part of the European GeoMed project, which will be discussed briefly before we say something about the pilot application we are developing together with the City of Bonn.

8. N.I. Karacapilidis, D. Papadias and M.J. Egenhofer, Collaborative Spatial Decision Making with Qualitative Constraints, Proceedings of the 3rd International ACM Workshop on Advances in Geographic Information Systems, Baltimore, Maryland, December 1-2, 1995, pp. 53-59.

   Usually spatial planning problems involve a large number of decision makers with different backgrounds and interests. The process of Collaborative Spatial Decision Making (CSDM) has to reconcile the individual approaches and lead to solutions that satisfy all participants. In this paper we deal with a particular instance of CSDM that involves qualitative constraints. Qualitative CSDM is very important for practical applications where decision makers communicate spatial knowledge using relations in space rather than absolute coordinates. It is also an interesting topic from the scientific point of view, because it combines several research areas related to Geographic Information Systems such as Spatial Query Languages, Constraint Satisfaction Mechanisms, Heterogeneous Databases, Spatial Access Methods and Group Decision Making. We describe the problems that need to be dealt with, we outline solutions, and we propose a computational model that can automate a large party of Qualitative CSDM.

9. N.I. Karacapilidis and D. Papadias, A TMS-based approach for efficient conflict resolution and replanning in resource allocation problems, Proceedings of 6th International Conference on Manufacturing Engineering (ICME-95), Melbourne, Australia, November 29-December 1, 1995, pp. 461-466.

   This paper describes how results from Truth Maintenance Systems and Temporal Abstraction Techniques can be combined for efficient problem solving. The above combination is proved useful for problems in which temporal abstractions are inherent such as resource allocation problems. The temporal abstraction techniques hat are involved here are: temporal summarization, that replaces a set of time intervals by a single one, and the value-assignment delay heuristic that decomposes the problem into clusters of variables, based on the ease a resource can be assigned. The proposed formalism provides an architecture for the representation of consistency as well as a problem solving framework that efficiently resolves conflicts on resources contention and manipulates rescheduling with the minimum effort. The need for backtracking is limited and rescheduling is rendered a quite easier and faster task.

10. G.I. Adamopoulos, C.P. Pappis and N.I. Karacapilidis, A hybrid heuristic method for scheduling with fuzzy due-dates , Proceedings of the 3rd Balkan Conference on Operational Research, Thessaloniki, Greece, October 16-19, 1995.

    In this paper we deal with a single machine bicriterion scheduling problem, assuming fuzzy due dates and controllable processing times. The objective is to maximize the grade of satisfaction incurred by the jobs' compression, subject to limited processing cost. The latter is a linear function of the jobs' compression. The problem is solved via a hybrid approach which encapsulates concepts from Tabu Search, Genetic Algorithms and Simulated Annealing. Both Complete Enumeration and Branch and Bound techniques were used to evaluate the efficiency of the proposed method.

11. N.I. Karacapilidis, Planning under Uncertainty: A Qualitative Approach, in C. Pinto-Ferreira and N.J. Mamede (eds.) Progress in Artificial Intelligence, Proceedings of the 7th Portuguese Conference on Artificial Intelligence (EPIA-95), Funchal, Portugal, October 3-6, 1995, Springer-Verlag, Berlin, Lecture Notes in AI, Vol. 990, 1995, pp. 285-296.

    Hierarchical planners create descriptions of abstract states and divide their planning task into subproblems for refining these states. In spite of their success in reducing the search space, they classically assume the existence of certain and complete information. In real world planning instances, one has to select among alternative strategies at each abstract state, observing both incomplete knowledge of the attributes that each strategy may pose, and partial ordering of these attributes. In addition, reasoning is defeasible: further information may cause another alternative to be more preferable than what seems optimal at the moment. This work presents a planning framework based on qualitative value decision making formalisms. Sketching the appropriate strategy operator schemata for hierarchical planning, it focuses on aspects of uncertainty handling by combining abilities of constraint programming languages with the introduced concepts of credulous and skeptical conclusions of an issue. The topics of argumentation among the planning agents and common conflicts in the ordering of defaults are discussed by means of a real planning example.

12. N.I. Karacapilidis and T. Gordon, Dialectical Planning, Proceedings of the 14th International Joint Conference on Artificial Intelligence (IJCAI-95) Workshop on Intelligent Manufacturing Systems, Montreal, Canada, August 19-25, 1995, pp. 239-250. Also in J. Sauer, A. GŸnter and J. Hertzberg (eds.) Planen und Konfigurieren 96 , Proceedings of the 10th Workshop Planen und Konfigurieren (PuK 96), Bonn, Germany, April 15-17, 1996, Infix-Verlag, Sankt Augustin, Proceedings in Artificial Intelligence series, Vol. 3, 1996, pp. 205-216 (with minor changes and under the subtitle Designing a mediating system for group decision making).

    Planning of real world instances has to be performed through a lot of debates, negotiations and arguments between groups of planning agents. Conflicts of interest are inevitable and support for achieving consensus and compromise is required. The identification and selection among alternative courses of action have to be supported with rational, fair and effective decision-making models, especially in the prevailing cases of limited and uncertain information. Dialectical Planning is among the most promising application areas for what we call Computational Dialectics, that is computational models of norms of rational discourse. Work presented in this paper focuses on the design and implementation of such a mediating system for supporting group planning founded on a normative model of limited rationality.

13. N.I. Karacapilidis and D.G. Pothos, On achieving arc consistency in scheduling problems, in G. Liu et al. (eds.) Optimization: Techniques and Applications , Proceedings of the 3rd International Conference on Optimization Techniques and Applications (ICOTA-95), Chengdu, China, June 12-15, 1995, World Scientific, 1995, pp. 803-812.

    The formulation of classical scheduling problems as Constraint Satisfaction Problems receives recently great attention. This paper is focused on the subsequent enforcement of enhanced arc consistency techniques in these problems. Cases of local consistency are presented and their relative computational complexity with backtracking is indicated. Consistency enforcing is exemplified with a job-shop scheduling problem where set-up times are involved between the successive processing of two jobs. The inherent precedence and capacity constraints of the problem are exploited with the proposed consistency enforcing schemes leading to a significant pruning of the corresponding search tree.

14. N.I. Karacapilidis, T. Brown and E.H. Mamdani, OR and KBS interworking for enhanced decision support, Proceedings of the International AMSE Conference Information Processing '94 , New Orleans, LA, November 9-11, 1994, AMSE Press, Vol. 1, pp. 25-35.

    The interworking of classical Operational Research techniques and Knowledge-Based Systems' approach is highlighted in this paper. The strict and quantitative character of the former is in contrast to the human-style subjective and qualitative nature of the latter. Difficulties that result from the sole use of Operational Research techniques suggest their co-operation with KBSs as desirable. RACE-II project DESSERT has been used as a test-bed for the specification and validation of relationship types between various OR and KBS methods of interworking. Various instances of the project that are characterised by the above co-operation are discussed, displaying the enhancement of the resulting decision support.

15. N.I. Karacapilidis, C.P. Pappis, S.N. Pantazopoulos and G. Adamopoulos, Designing a DSS for production planning and scheduling in the textile industry, in J. Janssen and C.H. Skiadas (eds) Applied Stochastic Models and Data Analysis, Proceedings of the 6th International Symposium on Applied Stochastic Models and Data Analysis, Chania, Greece, May 3-5, 1993, World Scientific, 1993, pp. 466-477.

    This paper presents YFADI (meaning weft in greek language), a computerized Decision Support System (DSS), for the production planning and scheduling in the Textile Industry. The design of the system aims at an efficient production management applied to multiple products. The system takes under consideration the specific characteristics of the Textile Industry, with its mixed production system (job-shop and flow-shop), but it can also easily fit to any similar environment. Its main elements are: (i) a database management system, (ii) a model based management system for formulating system models and algorithms, (iii) a set of modules for the interpretation and analysis of the production planning and scheduling problems, and (iv) an intelligent user interface for an effective communication between the user and the DSS.

16. C.P. Pappis and N.I. Karacapilidis, The location-allocation problem in a bottling company, in G. Feichtinger et. al. (eds) Methods of Operations Research 64, Proceedings of the International Conference on Operations Research, Vienna, Austria, August 28-31, 1990, Verlag Anton Hain, 1991, pp. 427-440.

    A method to solve the location-allocation problem concerning the distribution system of a Greek bottling company is presented in this paper. The method assumes the maximum allowable distance between a customer and the respective supplying center as the decisive parameter of the problem. The computer programs whice are employed for the solution of the problem are also presented.