In the first chapter, we learned that sketches raise the problem of distinguishing necessary from accidental properties, necessary properties being crucial for the purpose of sketch comparisons. In our thesis we propose to recognise them using perceptually or mentally aided distinctions. The first step in achieving this is to get a general idea of what representations are based on such distinctions. Several representations of perceptually aided spatial relations have been proposed in the field of qualitative spatial reasoning. But before we come to those representations we need to work out what is relevant when comparing sketches. It is primarily the imprecision of sketches that makes them difficult to handle. Hence, it is helpful to provide a framework for distinguishing different levels of spatial precision. We are then able to figure out where present approaches lack appropriate concepts for dealing with imprecise shape information such as that found in sketches.
KeywordsTopological Relation Shape Property Polygonal Approximation Spatial Precision Interval Relation
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