Modelling product ontology with CQL

For the selection of an industrial product, detailed product specification is indispensable. ISO13584 Parts Library (PLIB) is an International Standard that defines how the specification of a product can be exchanged using ISO10303 physical file format. However, this does not provide a standardized means of query about objects in the library, nor the differential transfer of ontology of products between different implementations based on the standard. Moreover, a standard gradually evolves over time in its syntax and semantics. Thus metadata migration as well as data migration between data models conforming to different versions of the standard becomes indispensable. This poses a serious problem since the entities in the PLIB are expressed in an object- oriented manner, while the database query languages currently available such as SQL (Structured Query Language) or OQL (Object Query Language) are either about relational databases that have no class hierarchy, or about Object-oriented databases whose class construction and queries depend on embedded language such as C++or Java. CQL (Class Query Language), presented herein, is to address this problem. The language is a declarative query language about an ontology represented in an object-oriented class hierarchy, based on the mathematical class concept known as ZFC (Zermelo-Fraenkel set theory with axiom of Choice). Furthermore, the language enables Boolean operations between classes whose properties are not necessarily the same. Thus, the language is a theoretical extension of the SQL to the object-oriented modelling domain. This paper describes the mathematical foundation of CQL and illustrates the syntactic characteristics of the language.