EVALUATING RECURSIVE QUERIES IN CAD USING AN EXTENDED PROJECTION FUNCTION.

Abstract

Entities such as mechanical assemblies are recursive when they contain other assemblies at a lower level of detail. The authors show how recursive CAD entities can be manipulated using an extended projection function. The function finds nested subentities within entities that are modeled as trees of aggregations and generalizations. It allows these subentities to be found using expressions that are independent of the complexity of an entity's data structure. A description is given of the function, its relationship to the transitive closure function, and its implementation in a CAD database system.