Boris Pasternak, Gabriel Gabrielides, Rainer Sprengel

1992, Memo, 32 pages, English text

Abstract:

This report describes the design and development of a prototype for the interpretation of technical drawings, called WIZ. The report introduces drawing interpretation as a knowledge processing task. At first, the state of the art in drawing analysis is examined. Then, starting from a discussion about the necessary kinds of knowledge to perform drawing interpretation, we present our frame-based knowledge structure and explain its implementation using a generic blackboard model. This allows easy adaptibility to new application domains. The main part of the report deals with the basic interpretation cycle which exploits a-priori knowledge about the drawing structure and associated geometrical constraints. This is discussed in detail for an example from the area of engineering drawings. The interpretation starts with the vectorization primitives and stops when physical objects (axles, cylinders, etc.) and non-physical dimensioning objects (dimension sets, metric arrows, etc.) are recognized. It is shown that the results of drawing interpretation can be used for domain specific tasks, e.g. dimension checking or drawing redesign. Finally, a graph-based strategy for dimension checking is described in detail.