Study Of Design Patterns

Abstract Design Patterns is a kind of new technique for supporting software development and design reuse emerging recently. Presently, researches on design patterns mainly focus on finding new ones and the applications of some of them. But its concepts is not very clear and description is not perfect now, which are obstacles to its further researches, the development of related tools and its applications. In this paper, a two梩ier model describing design patterns is presented, ahd on the basis of the model, a consistent formal specification is given It separates the abstract object collaboration relations with its concrete implementation structure, expands the implementation space of design patterns, and describes the composition relations of design patterns and Composite Patterns appropriately. By using the Extension Mechanisms of Unified Modeling Language(UML), we integrate description model of design patterns with UML, and implement it in Rose98, which establishes the basis of combining design patters and current Object桹riented methods. A Composite Pattern is presented, which provide a hierarchical structure of composite components that is capable of maintaining its inner state consistency, accepts interaction with client on any level in the hierarchical, and support the encapsulation, dynamic creation and dynamic composition of the components. The application of the Composite Pattern in VA framework is analyzed, and the design pattern reuse in the development of Chinese report component is given.