From dynamic supertypes to subjects: A natural way to specify and develop systems

When we understand, specify, and develop systems, we use certain concepts and constructs to deal with complexity. Object-oriented (OO) approaches provide good ways for doing so. However, many existing OO approaches (perhaps based on object models used in existing OO languages) cannot solve important problems encountered in large and complex systems. For example, we often have to deal with properties of ''things'' that cannot be represented in a neat hierarchy. Some of these properties may significantly change with time. Moreover, many of these properties refer to collections of objects without identifying a single object as ''owner'' of each property. The authors of this technical note have separately proposed approaches for solving these problems, but at very different stages of the development life cycle. However, the underlying concepts of these approaches are so close that they can be successfully combined to provide a common solution that encompasses all stages of the life cycle.