Patterns, frameworks, and middleware: their synergistic relationships

The knowledge required to develop complex software has historically existed in programming folklore, the heads of experienced developers, or buried deep in the code. These locations are not ideal since the effort required to capture and evolve this knowledge is expensive, time-consuming, and error-prone. Many popular software modeling methods and tools address certain aspects of these problems by documenting how a system is designed However they only support limited portions of software development and do not articulate why a system is designed in a particular way, which complicates subsequent software reuse and evolution. Patterns, frameworks, and middleware are increasingly popular techniques for addressing key aspects of the challenges outlined above. Patterns codify reusable design expertise that provides time-proven solutions to commonly occurring software problems that arise in particular contexts and domains. Frameworks provide both a reusable product-line architecture [1] - guided by patterns - for a family of related applications and an integrated set of collaborating components that implement concrete realizations of the architecture. Middleware is reusable software that leverages patterns and frameworks to bridge the gap between the functional requirements of applications and the underlying operating systems, network protocol stacks, and databases. This paper presents an overview of patterns, frameworks, and middleware, describes how these technologies complement each other to enhance reuse and productivity, and then illustrates how they have been applied successfully in practice to improve the reusability and quality of complex software systems.