Qualitative representation of planar outlines
Richard Meathrel, Antony Galton · European Conference on Artificial Intelligence · 2000
A new boundary-based scheme for qualitatively representing planar outlines is described, consisting of a set of seventeen tokens, and based on a combined discretisation of tangent bearing, curvature, and the rate of change of curvature. By grouping together strings of atomic tokens, higher-level primitive curve tokens can be specified (PCTs), that correspond to localised curve features of greater abstraction. We show how the primitives of existing boundary-based schemes may be defined as PCTs, and how associated token ordering graphs can be constructed that visually encode token-string syntax, based on the ordering constraints implicit in a set of PCT specifications. Because of the atomic nature of its building blocks, we propose that the scheme can be developed into a general framework for constructing sets of task-specific primitives, for use in application areas such as computer vision and qualitative spatial reasoning.