Aspect-oriented approach to early design modelling

Developers of modern software systems are often required to build software that addresses security, fault-tolerance and other dependability concerns. A decision to address a dependability concern in a particular manner can make it difficult or impossible to address other concerns in software. Proper attention to balancing key dependability and other concerns in the early phases of development can help developers better manage product risks through early identification and resolution of conflicts and undesirable emergent behaviours that arise as a result of interactions across behaviours that address different concerns. The authors describe an aspect-oriented modelling (AOM) approach that eases the task of exploring alternative ways of addressing concerns during software modelling. The paper focuses on use of the AOM approach to produce logical, aspect-oriented architecture models (AAMs) that describe how concerns are addressed in technology-independent terms. An AAM consists of a set of aspect models and a base architecture model called the primary model. An aspect model describes how a dependability concern is addressed, and a primary model describes how other concerns are addressed. Composition of the aspect and primary models in an AAM produces an integrated view of the logical architecture described by the AAM. Composition can reveal conflicts and undesirable emergent properties. Resolving these problems can involve developing and analysing alternative ways of addressing concerns. Localising the parts of an architecture that address pervasive and nonorthogonal dependability concerns in aspect models allows developers to more easily evolve and replace the parts as they explore alternative ways of balancing concerns in the early stages of development.