Framework Composition: Problems, Causes and Solutions

Reuse of software has been one of the main goals of software engineering for decades. With the emergence of the object-oriented paradigm, an important enabling technology for reuse of larger components became available and resulted in the definition of object-oriented frameworks. Our and others experiences with frameworks have shown that frameworks indeed provide considerable reuse in framework-based application development. However, whereas framework-based application development initially included a single framework, increasingly often multiple frameworks are used in application development. These frameworks have to be composed, but the software engineer may experience a number of problems while doing this, related to (1) composition of framework control, composition with legacy components, (3) framework gap, (4) overlap of framework entities and (5) composition of entity functionality. The primary causes for these composition problems are related to (1) the cohesion between classes inside each framework, (2) the domain coverage of the frameworks, (3) the design intentions of the framework designers and (4) the potential lack of access to the source code of the frameworks. Based on the identified problems and causes, we analyse the existing solutions and their limitations.