Modeling evolving information about engineering design products: An object-centered approach combining description logic and object-oriented modeling.

摘要

Engineering design is one of the most challenging application areas for computer-based systems. Engineering design requires the creation of, and the manipulation of, complex entities that are linked by various semantic relationships. The descriptions of these design entities and the relationships between them change throughout the design process. A computer-aided design environment that assists with the design of engineering products should not only support the representation of the end product model and the relationships among its components, but also the evolution of these components and relationships during the design process. In addition, several different views of a design product must be generated and maintained. A representation of design product models should be flexible enough to allow the incremental generation and manipulation of these views. Various data types and knowledge formalisms are usually used by designers to describe the products of their designs. The diversity of the data types that describe design products and the knowledge sources that reason with this data creates the need for a flexible environment that supports various data types and multiple knowledge representation paradigms. The design product must also be modeled and viewed at multiple levels of abstraction. Finally, since the design process is mainly driven by design constraints which play an essential role in the evolution of design products, a flexible constraint representation mechanism which allows for instance-specific constraints as well as class-defined constraints should be incorporated in a semantic representation of design product models.;This document presents an object-centered approach for representing engineering design product models based on combining description logic with object-oriented techniques. The object-centered approach is superior to its counterpart, the class-centered approach, in that objects can be created and manipulated independently from the schema classes, and are automatically classified under appropriate concept classes for which they satisfy membership sufficiency conditions. I demonstrate how the object-centered approach overcomes the limitations which render the class-centered approach inadequate for representing evolving design product models. These limitations include the lack of mechanisms for object evolution, schema evolution, representing partial information about objects, classification, recognition of objects, and constraint management. In the proposed object-centered approach, an evolving model of a design product is represented as a collection of interrelated design entities and design aspects that describe the various characteristics of this design product. The various views of a design product are represented as one or several hierarchies of design aspects. Design aspects from different views are grouped together by various semantic relationships to form design entities which are used as building blocks for the design product model. Description logic was chosen to implement the object-centered approach because it provides important services for design product modelers such as: data definition language, data manipulation language, incomplete data representation, subsumption of concepts, instance recognition, and integrity constraint checking. A modeling environment called SHADES which combines description logic and object-oriented modeling for representing engineering design product models was developed and is described in this document. The object-centered approach for modeling design products is demonstrated through illustrative examples and its advantages are discussed in detail.