Coverages are of two types. A discrete coverage has a domain that consists of a finite collection of geometric objects and the direct positions contained in those geometric objects. A discrete coverage maps each geometric object to a single record of feature attribute values. The geometric object and its associated record form a geometry value pair. A discrete coverage is thus a discrete or step function as opposed to a continuous coverage. Discrete functions can be explicitly enumerated as (input, output) pairs. A discrete coverage may be represented as a collection of ordered pairs of