A product configurator can be defined as a product-oriented expert system (or knowledge-based system) that allows users to specify products by selecting components and properties under the restriction of valid combinations. For several industrial companies, the use of configurators has produced a range of benefits, such as: shorter lead times (sales to delivery), improved quality of product specifications, preservation of knowledge, fewer resources used to specify products, optimized products, less routine work, improved certainty of delivery, and less time required to train new employees [6,7,14,23,25].
Development of a product configurator implies that domain expert knowledge is elicited and then represented in the product configurator. The representation of domain knowledge is often one of the most demanding tasks in a product configuration project [3,11,15,24]. In order to be able to describe domain expert knowledge in a form that allows it to be implemented in the knowledge base of a configurator, two distinctive kinds of models are often applied, namely analysis models and design models. Analysis models (also called domain or conceptual models) are used to describe a real world domain of interest before initiating design and coding [22]. In configuration projects, analysis models can be understood as mediators between product technical domain experts and knowledge engineers, in the sense that analysis models can be used to capture what the domain experts articulate and let the domain experts then evaluate whether the captured knowledge is correct. The model that specifies what should be implemented in the configurator software is called a design model. Since the analysis phase usually involves product experts who are often without much diagrammatic modelling qualifications, the requirements for the analysis language often focus on user-friendliness. Design models, on the other hand, are typically created by persons who are familiar with diagrammatic modelling. Therefore, the requirements for a design language focus on how well the language facilitates expression in a sufficiently exact and formalized manner of what should be implemented in the configurator, rather than easy comprehension. In configurator literature that deals with diagrammatic representation techniques, two types of diagrams are often mentioned, namely product variant masters (PVMs) and class diagrams (both described in the following section). While class diagrams are richer, more flexible Computers in Industry 61 (2010) 409-418