A comparison of design patterns and roles in the context of behavioural evolution

Component-based software development focuses on building software systems by integrating existing software components. Central to component-based software development are the notions of reusability, extensibility and adaptability. Components as well as their composition must be easily reused and extended to meet new requirements. Variation-oriented programming is concerned with the incorporation of context-dependent variations in existing object-oriented systems. Based on the principle of separation of concerns, variation-oriented programming addresses amongst other issues - behavioural evolution and behaviour composition, at runtime. We identify the limitations imposed by the use of design patterns when used for behavioural evolution, in terms of behaviour composition, while at the same time satisfying reusability and extensibility. Then we proceed to present the ATOMA framework as an architecture and a means for achieving behaviour composition, as this is guided by the incorporation of context-dependent behavioural variations based on the concept of roles. Roles axe considered, in this light, as pluggable behavioural adjustments of an existing object-oriented system.