Software Architecture: Foundations, Theory, and Practice

Chapter 14. Architectural Adaptation

Few applications are designed, built, used, and ultimately discarded without undergoing change. Change is endemic to software: Both the perceived and actual malleability of the medium, coupled with the ease of altering code, induces everyone associated with an application to initiate changes. Users change their minds about what they want and hence what they require of an application. Designers seek to improve their designs with respect to performance, or appearance, or some other property. The application's usage environment can change. Whatever the reason, software developers are faced with the challenges of coping with the need to modify an application. We group all of these types of changes under the term adaptation : modification of a software system to satisfy new requirements and changing circumstances.

Adaptability was introduced in Chapter 12 as one of several non-functional properties for which architects must frequently design. Several basic architectural techniques supporting adaptation were presented. Just as Chapter 13 was devoted to in-depth exploration of the non-functional properties of security and trust, so this chapter delves further into adaptability. Nonetheless, this chapter does not aspire to present techniques for dealing with all possible types of adaptation at all levels of granularity and abstraction—to do so would require a book of its own. Consistent with the focus of the book, our discussion is centered on facilitating ...