In this paper we study the problem of concept contraction for the description logic EL. Concept contraction is concerned with the following question: Given two concepts C and D (with the interesting case being that D subsumes C) how can we find a generalisation of C that is not subsumed by D but is otherwise as similar as possible to C? We take an AGM-style approach and model this problem using the notion of a concept contraction operator. We consider constructive definitions as well as sets of postulates for concept contraction,and link the two by means of representation theorems.

We examine the problem of partitioning a square into convex polygons which are as circular as possible. Circular means that the polygon's aspect ratio is supposed to be near 1. The aspect ration of a convex polygon denotes the ratio of the diameters of the smallest circumscribing circle to the largest inscribed disk. This problem has been solved for the equilateral triangle as well as for regular k-gon with k > 4. In the case of a square, the optimal solution is still an open problem. We are planning to find a solution which is ldquogood enoughrdquo with the help of evolutionary algorithms.