Prediction as a Knowledge Representation Problem : A Case Study in Model Design

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(1)Linköping Studies in Science and Technology. Thesis No. 942. Prediction as a Knowledge Representation Problem: ACase Study in Model Design by. P@trik Haslum. Submitted to the School of Engineering at Linköping University in partial fulfilment of the requiremens for degree of Licentiate of Engineering Department of Computer and Information Science Linköpings universitet SE-581 83 Linköping, Sweden. Linköping 2002.

(2) Tryckt av Unitryck, Linköping, Sverige, 2002. ISBN 91-7373-331-8 ISSN 0280-7971.

(3) Prediction as a Knowledge Representation Problem: ACase Study in Model Design by P@trik Haslum April 2002 ISBN 91-7373-331-8 Linköping Studies in Science and Technology Thesis No. 942 ISSN 0280-7971 LiU-Tek-Lic-2002:15 ABSTRACT The WITAS project aims to develop technologies to enable an Unmanned Airial Vehicle (UAV) to operate autonomously and intelligently, in applications such as traffic surveillance and remote photogrammetry. Many of the necessary control and reasoning tasks, {\it e.g.} state estimation, reidentification, planning and diagnosis, involve prediction as an important component. Prediction relies on models, and such models can take a variety of forms. Model design involves many choices with many alternatives for each choice, and each alternative carries advantages and disadvantages that may be far from obvious. In spite of this, and of the important role of prediction in so many areas, the problem of predictive model design is rarely studied on its own. In this thesis, we examine a range of applications involving prediction and try to extract a set of choices and alternatives for model design. As a case study, we then develop, evaluate and compare two different model designs for a specific prediction problem encountered in the WITAS UAV project. The problem is to predict the movements of a vehicle travelling in a traffic network. The main difficulty is that uncertainty in predictions is very high, due to two factors: predictions have to be made on a relatively large time scale, and we have very little information about the specific vehicle in question. To counter uncertainty, as much use as possible must be made of knowledge about traffic in general, which puts emphasis on the knowledge representation aspect of the predictive model design. The two model designs we develop differ mainly in how they represent uncertainty: the first uses a coarse, schema-based representation of likelihood, while the second, a Markov model, uses probability. Preliminary experiments indicate that the second design has better computational properties, but also some drawbacks: model construction is data intensive and the resulting models are somewhat opaque. This work has been supported by the Knut and Alice Wallenberg Foundation, and the ECSEL graduate studies program.. Department of Computer and Information Science Linköpings universitet SE-581 83 Linköping, Sweden.

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