Component Publications and Compositions

One of the major issues in component-based design is how to use a component correctly in different applications according to the given interface specification, called the

publication

, of the component. In this paper we formulate this as the problem of component publication composition and refinement. We define the notion of publications of components that describes how a component can be used by a third party in building their own components or in writing their applications without access to the design or the code of the component. It is desirable that different users of the components can be given different publications according to their need. The first contribution of this paper is to provide a procedure, which calculates a weakest contract of the required interface of a component from the contract of its provided interface and its code. The other contribution, that is more significant from a component-based designer’s point of view, is to define composition on publications so that the publication of a composite component can be calculated from those of its subcomponents. For this we define a set of primitive composition operators over components, including

renaming

,

hiding

,

internalizing

,

plugging

and

feedback

. This theory is presented based on the sematic model of rCOS, a refinement calculus of component and object systems.