Object Naming and Object Composition

In this paper, we show that a flat domain of object names is inappropriate in the context of object composition since new naming requirements must be fulfilled. These requirements can be summarized by: (1) visibility and hiding of components, (2) checking whether two objects belong to the same composition, (3) sharing of components between compositions, (4) reference from one composition to another composition. Object naming in the object paradigm is based on the use of the concept of object identity which can be considered as an intrinsic and universal name of the object. It does not record information about the structure of objects. This naming mechanism is inadequate for fulfilling the requirements stated above. For instance, once you have the identity of an object you can access that object. This means you can not achieve component hiding within the composition. There are many alternatives for solving this problem including the design of complex naming mechanisms. Our solution consists of recognizing that referencing objects is contextual while the concept of object identity is context independent. Based on this observation, we view the execution of an application as an evolving structure of labelled graphs of objects. Each state of the application is represented by a graph of objects. This allows us to use the concept of sense of direction [Floc98a] for designing various kinds of naming mechanisms. In this paper, we designed three naming mechanisms using sense of direction. The first is based on a chordal sense of direction. The second is hierarchical naming without component sharing. The last is a slight modification of the second to allow component sharing. This is achieved by introducing special names for shared components.