Software architecture alludes to “the overall structure of the software and the ways in which that structure provides conceptual integrit...
Software architecture alludes to “the overall structure of the software and the ways in which that structure provides conceptual integrity for a system” [SHA95a]. In its simplest form, architecture is the hierarchical structure of program components (modules), the manner in which these components interact and the structure of data that are used by the components. In a broader sense, however, components can be generalized to represent major system elements and their interactions.
One goal of software design is to derive an architectural rendering of a system. This rendering serves as a framework from which more detailed design activities are conducted. A set of architectural patterns enable a software engineer to reuse designlevel concepts.
Shaw and Garlan describe a set of properties that should be specified as part of an architectural design:
Structural properties. This aspect of the architectural design representation defines the components of a system (e.g., modules, objects, filters) and the manner in which those components are packaged and interact with one another. For example, objects are packaged to encapsulate both data and the processing that manipulates the data and interact via the invocation of methods.
Extra-functional properties. The architectural design description should address how the design architecture achieves requirements for performance, capacity, reliability, security, adaptability, and other system characteristics.
Families of related systems. The architectural design should draw upon repeatable patterns that are commonly encountered in the design of families of similar systems. In essence, the design should have the ability to reuse architectural building blocks.
Given the specification of these properties, the architectural design can be represented using one or more of a number of different models . Structural models represent architecture as an organized collection of program components. Framework models increase the level of design abstraction by attempting to identify repeatable architectural design frameworks (patterns) that are encountered in similar types of applications. Dynamic models address the behavioral aspects of the program architecture, indicating how the structure or system configuration may change as a function of external events. Process models focus on the design of the business or technical process that the system must accommodate. Finally, functional models can be used to represent the functional hierarchy of a system.
A number of different architectural description languages (ADLs) have been developed to represent these models . Although many different ADLs have been proposed, the majority provide mechanisms for describing system components and the manner in which they are connected to one another.
