ARCHITECTURA L ADAPTATION TALIESIN SMITH

CONCEPTS Adaptation – Modification of a software system to satisfy new requirements and changing circumstances Agent – People and/or software that perform the change Context – The factors behind the motivation for change

SOURCES AND MOTIVATION Corrective change Functional requirements Non-functional requirements Operating environment

SOURCES AND MOTIVATION Product-line forces New variant New branch point Merging product lines Observation and Analysis

BUILDING ANALOGY A building is made up of various layers Some layers are harder to change than others All layers change with varying frequency Architectural erosion

BUILDING ANALOGY Identify how layers interact Separate layers so that changing one affects few others Make changes based on complete structure, not local Look at overall effects of change, then incorporate changes down into local code

ELEMENTS SUBJECT TO CHANGE - COMPONENTS To facilitate adaptation, give components the following capabilities Self-knowledge and exposure of such to external entities Self-knowledge of component’s role in larger scheme Proactively engage other elements to adapt

ELEMENTS SUBJECT TO CHANGE - INTERFACES Changing interfaces requires changing that which they interface to Create adaptors that take data, translate, and pass on to the component This creates problems after too many changes

ELEMENTS SUBJECT TO CHANGE - CONNECTORS Usually changed to achieve new or different non- functional properties The more powerful the connector, the easier the adaptation

AGENTS Identity and Location Humans can deal with a wider range of problems Programs can identify and fix problems faster If agent is deployed with the system, it need not get to the application and has access to more contextual information Knowledge Risks, constraints, etc.

CONTEXT Timing The earlier change is initiated, the better Difficulty increases sharply after deployment Degree of Freedom More freedom is not always better Increases search space and decreases initial guidance Cost can be decreased by doing lower-quality assessment, but results in possible degradation o f the system

CONCEPTUAL FRAMEWORKS