Task-driven descriptions of mechanical parts in a CAD system

A feature recognition system is described for the detection of shape features which allow the performance of a task in a given working environment. The features are recognized in a technical drawing or in a 3D CAD model describing the part to be managed. The output of the recognition processes represents the recognized features as volumes in a hybrid gfeometric model. The system is designed by using Conditional Attributed IL Systems, that allow the representation of both boundary models and technical drawings describing the solid as string of attributed symbols. These strings are rewritten by the use of rules describing features according to a given working context. The recognized features are in any case denoted by sets of symbols corresponding to volumetric representations.