| Feature modeling is product-oriented and it is an important milestone of CAD development, which really makes integrated CAD/CAPP/CAM possible. It is also the theory and technological foundation of solving products problems. Semantic feature modeling is a declarative feature modeling approach that not only provides a well-defined specification of feature semantics, but also effectively maintains this semantics during the modeling process. In fact, one of the basic ideas of feature–based modeling is the ability to associate functional information to shape information in a feature model, which form the semantic of the feature together. Bidarra,R. researches feature semantics, e.g. the detailed description of feature class, and describes that validity maintenance of semantic feature models is its final aim. Feature class specification is classified into three categories: (1) specification of feature parameterized shape that encapsulates elements, parameters and natures of feature shape; (2) specification of feature validity conditions that involves a variety of constraints such as algebraic constraint, dimension constraint, semantic constraint and interaction constraint; (3) interface of user-supplied data to the feature model that determines the appropriate normal positions and orientations such as attach constraint and geometric constraint. Embedding validity criteria in each feature class makes feature adjustable, provide the mechanism of shape inheritance and shape composition in order to achieve the user-defined and compound feature. So it enhances the efficiency of designing process and improves the ability of modeling. Feature model validity maintenance is the process of monitoring each modeling operation in order to ensure that all features in feature model conform to the semantics specified in their respective classes. The basic principles of validity maintenance can be summarized as follows: (1) A modeling operation, to be considered as valid, should yield a feature model that conforms to all constraints. This ensures that every feature in the model conforms to the designer intent explicitly specified up to that moment. (2) After an invalid modeling operation, the user should be assisted in overcoming the constraint violations in order to recover model validity again. Maintaining feature model validity, e.g. feature semantic validity is by means of validity constraints that is the member in the definition of feature. At the creation of a feature and later modeling step, validity checking, whether those constraints are valid, indicates feature validity. Many validation violations, e.g. constraint violations are caused by feature interaction. So feature interactions play a major role in semantic feature modeling system, either the specification of feature class or validity maintenance of feature model. To the above analysis, this paper analysis the semantic feature modeling of new generation, consult research results of Bidarra, etc and use validity criterion, establish recognition methods of intersecting feature to semantic feature modeling. This paper bases on the solution of restriction, set up the theory of intersecting feature recognition mechanism, maintain validity of feature model, thus to make product model editing easier. Based on research results, we do further improvement and perfection to the owner-copyright industry modeling system (HUST-CAIDS) that is developed independently, make the product design of CAID meet project designer's needs even more. CAID system faces the industrial shape-designing software system of the engineering products, it has shortened the design cycle of product development, have improved the added value of the products. Through further investigation in the aspects of subject, this paper offers a new theory and method for key technology of the semantic feature modeling and domestic CAD software development. It can make CAID software system user -oriented need for enormous economic benefits and social benefit.
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