A software architecture is the result of multiple decisions made by a software architect. These decisions are called architectural decisions, as they bring solutions to architectural problems. Relations between decisions can be captured in architectural decision models. Such models are then a form of reusable knowledge for software architects. Several models have been described in the literature, introducing necessary concepts and relations. These concepts and relations were usually explained using natural language. Not much work has been done so far on their formal definitions. Specifically, such a definition of an architectural decision model is still missing. The purpose of this paper is filling this gap by providing the formal definition of an architectural decision model at both syntax and semantics levels. At the syntax level, different concepts and relations that are elements of a model have been mathematically defined. At the semantics level, the meaning of a model has been defined in a form of denotational semantics. The formalization not only allows for better understanding of architectural decision models but opens the possibility to reason on such models, e.g., checking their consistency - something that is very limited for the models proposed so far. A practical example of the semantics of an architectural decision model is also presented.
@cite_6 , decisions made are distinguished from decisions required from the architect. The proposed UML metamodel for capturing architectural decisions contains, among others, three core entities: , and . An instance of ADIssue (an architectural decision issue) informs the architect that a single architecture design problem has to be solved, whereas instances of ADAlternative (architectural decision alternatives) present possible solutions to this problem. These two entities provide reusable background information. Finally, instances of ADOutcome (architectural decision outcomes) present an actual decision made to solve the problem including its rationale. The mentioned UML metamodel is complemented with formal definitions for a rich set of relationships between alternatives, alternatives and issues, and issues alone. However, the formal definitions of their semantics are missing.
@cite_6
2162923122
Software architects consider capturing and sharing architectural decisions increasingly important; many tacit dependencies exist in this architectural knowledge. Architectural decision modeling makes these dependencies explicit and serves as a foundation for knowledge management tools. In practice, however, text templates and informal rich pictures rather than models are used to capture the knowledge; a formal definition of model entities and their relations is missing in the current state of the art. In this paper, we propose such a formal definition of architectural decision models as directed acyclic graphs with several types of nodes and edges. In our models, architectural decision topic groups, issues, alternatives, and outcomes form trees of nodes connected by edges expressing containment and refinement, decomposition, and triggers dependencies, as well as logical relations such as (in)compatibility of alternatives. The formalization can be used to verify integrity constraints and to organize the decision making process; production rules and dependency patterns can be defined. A reusable architectural decision model supporting service-oriented architecture design demonstrates how we use these concepts. We also present tool support and give a quantitative evaluation.