Non-intrusive Instance Level Software Composition

A software system is comprised of parts, which interact through shared interfaces. Certain qualities of integration, such as loose-coupling, requiring minimal changes to the software and fine-grained localisation of dependencies, have impact on the overall software quality. Current general-purpose languages do not have features that target these integration qualities at the instance level, hence they lack expressive power to define integration-specific code. As a result integration requires invasive code alterations, tightly coupled components that hinder maintainability and reuse. In this thesis, we focus on developing language extensions and frameworks, which offer a declarative way of defining the elements involved in the instance level software composition. Our motivation is that nonintrusive means of integration at the granularity of the instance level has an impact on the maintainability and the extensibility of the software. We focused on declarativeness since we want to improve how integration concerns are expressed in the implementation. We particularly focus on two challenges specific to the instance-level integration step; the two contributions proposed as a solution to each of these challenges both present declarative approaches for implementing specific concerns. These concerns are; 1. selecting objects based on how they are used in a system and, 2. non-intrusive implementation and injection of adapters. The first challenge is the difficulty of selecting objects based on other criteria than the type system. This is important during integration since, independent of their type, objects can become relevant to a component when they participate in specific events. Such events mark the phases in the life-cycle of objects. The phase in which an object currently is, affects how it is handled in an application; however phase shifts are often