This paper is concerned with the problem of intelligent understanding of engineering drawing. The presented method is based on the engineering semantics classification. The contribution of different kind of semantics and the relationships among them in engineering drawings understanding are firstly discussed

namely

expression mode semantics is the premise

projection relation semantics is the kernel and dimension constraint semantics is the elicitation. Then the technology of engineering semantics obtaining and the corresponding integration are mainly introduced

thus the functional semantics expressed through the engineering semantics information could be obtained. In the end

complete details are provided to illustrate the identification of simple features and the combined relationship among the primitives using this approach. This method has been successfully used in the prototype system and the expected results have been got. It shows that the drawing understanding could be simplified

the recognition and processing could be speed up

and furthermore

the understanding reliability could be enhanced by using the technology.