Definition and implementation of vague objects ?

Vagueness occurs often in spatial information. A concept is vague if objects exist that cannot be classified either to the concept or to its complement. Vagueness arises in the presence of borderline cases. Examples are soil maps, geological maps, forestry inventories, and vegetation maps. Soil classes, or vegetation classes are such that they cannot be defined sharply. The change from one class to another is gradual. Most work on vagueness in spatial information is dedicated to vague regions and topological relations between them. A vague region is a region with a broad boundary, i.e., its boundary is not a sharp line, but a zone of transition. Current work on vague regions either considers the broad boundary as a homogenous unit [1–3], or considers a gradual transition, so that points in the broad boundary have different degrees of membership to the region [4–7]. An example of the first is the so-called Egg-Yolk model [8, 9], based on mereology. The broad boundary region is seen as an egg, which is the whole region, and a yolk, which is the certain part of it. Topological relations between egg-yolk regions are defined based on Region Connection Calculus [10]. A second example ? The work is funded by the European Community, under IST-1999-14189 project