Complex Objects and Relationships
Engineering data have complex structures and are usually large in volume. But engineering design objects and their components are not independent. In particular, they are generally organized into taxonomical hierarchies. The specialization association is the well-known association. Also the part-whole association, which relates components to the compound of which they are part, is another key association in engineering settings.
In addition, the position relationships between the components of design objects and the configuration information are typically multi-dimensional. Also, the information of version evolution is obviously time-related. All these kinds of information should be stored. It is clear that spatio-temporal data modeling is essential in engineering design (Manwaring, Jones, & Glagowski, 1996).
Typically, product modeling for product family and product variants has resulted in product data models, which define the form and content of product data generated through the product lifecycle from specification through design to manufacturing. Products are generally complex (see Figure 1, which shows a simple example of product structure) and product data models should hereby have advanced modeling abilities for unstructured objects, relationships, abstractions, and so on (Shaw, Bloor, & de Pennington, 1989).
Figure 1. An example illustration of product structure