POP Frameworks: Amortizing the Cost of Using Applications as Components

Package-oriented programming (POP) is a promising approach to component-based software design. POP treats suites of massmarket application packages as component libraries. Their standardized architectures, programmability, interoperability, rich orthogonal functions, and low cost make them attractive candidates as components. However, they also have characteristics that make it hard and risky to find workable designs. Each designer has to face these difficulties and risks anew. We introduce the idea of POP frameworks as a means of amortizing the upfront cost of resolving these design problems over multiple applications. Like an object-oriented framework, a POP framework factors out the design and code common to a family of applications. The challenge that we face in designing POP frameworks is to understand and accommodate the unusual characteristics of POP components. We hypothesize that POP frameworks can significantly ease the task of developing families of POP-based applications. To evaluate this idea, we developed an experimental POP framework for a family of software tools and used it to instantiate two tools. The four contributions of this paper are the concept of POP frameworks, the analysis of the impact of contemporary POP component characteristics on framework design, a prototype POP framework for a particular family of tools, and experience that suggests that POP frameworks have the potential to advance our ability to build sophisticated new applications quickly and inexpensively.