Fundamenta Informaticae - Volume 57, issue 2-4

Authors: Dix, Jürgen | Eiter, Thomas | Fink, Michael | Polleres, Axel | Zhang, Yingqian

Article Type: Research Article

Abstract: In this paper we consider the following problem: Given a particular description of a multi-agent system (MAS), is it implemented properly? We assume that we are given (possibly incomplete) information about the system and aim at refuting its proper implementation. In our approach, agent collaboration is described as an action theory. Action sequences reaching the collaboration goal are computed by a planner, whose compliance with the actual MAS behaviour allows to detect possible collaboration failures. The …approach can be fruitfully applied to aid in offline testing of a MAS implementation, as well as in online monitoring. Show more

Keywords: knowledge representation, multi agent systems, planning

Citation: Fundamenta Informaticae, vol. 57, no. 2-4, pp. 345-370, 2003

Authors: Fichtner, Matthias | Großmann, Axel | Thielscher, Michael

Article Type: Research Article

Abstract: We present a robot control system for known structured environments that integrates robust reactive control with reasoning-based execution monitoring. It provides a robot with a powerful method for dealing with situations that were caused by the interaction with humans or that are due to unexpected changes in the operating environment. On the reactive level, the robot is controlled using a hierarchy of low-level behaviours. On the high level, a logical representation of the world enables the …robot to plan action sequences and to reason about the state of the world. If the execution of an action does not have the expected effect, high-level reasoning allows the robot to infer possible explanations and, if necessary, to recover from the failure situation. For the robot to act optimally, the discrepancies between the internal world model and the real world have to be detected and corrected. The proposed system obtains new information about the world by executing sensing actions (active perception) and by sensory interpretation during the robot's operation. It also takes into account temporal information about changes in the environment. All updates of the world model are performed in a way that the changes are consistent with an underlying action theory. Having implemented the proposed system on a common mobile robot platform, we demonstrate the value of intelligent execution monitoring by means of two realistic office delivery scenarios. Show more

Keywords: artificial intelligence, knowledge representation,

Citation: Fundamenta Informaticae, vol. 57, no. 2-4, pp. 371-392, 2003

Authors: Konczak, Kathrin | Schaub, Torsten | Linke, Thomas

Article Type: Research Article

Abstract: The integration of preferences into answer set programming constitutes an important practical device for distinguishing certain preferred answer sets from non–preferred ones. To this end, we elaborate upon rule dependency graphs and their colorings for characterizing different preference handling strategies found in the literature. We start from a characterization of (three types of) preferred answer sets in terms of totally colored dependency graphs. In particular, we demonstrate that this approach allows us …to capture all three approaches to preferences in a uniform setting by means of the concept of a height function. In turn, we exemplarily develop an operational characterization of preferred answer sets in terms of operators on partial colorings for one particular strategy. In analogy to the notion of a derivation in proof theory, our operational characterization is expressed as a (non–deterministically formed) sequence of colorings, gradually turning an uncolored graph into a totally colored one. Show more

Citation: Fundamenta Informaticae, vol. 57, no. 2-4, pp. 393-421, 2003