Systematic OO Programming with Axiomatic Design

A xiomatic design offers a systematic and orderly way to proceed through the software development process. The methodology ensures that developers make the best possible design decisions by providing decision-making criteria in the form of two axioms: • The independence axiom suggests that the best designs maintain the independence of the functional requirements, ensuring that the design can achieve each function without inadvertently affecting any other function. • The information axiom suggests that the best designs minimize their information content. Thus, the solution with the greatest likelihood of success is the simplest solution. Software developers can • determine the quality of the design based upon the degree to which it satisfies the defined functional requirements ; • ensure that the design satisfies each function independently and that coupling, which could cause unin-tended consequences, does not occur; • enjoy easier job assignment and team management because they can use the system architecture diagram to assign tasks and define the interrelationships between various modules or classes; and • handle software change orders quickly and easily because the system architecture identifies the modules affected by a change. Axiomatic design lets the developer document the design fully, making it easier to change or add extensions. Chronologically, axiomatic design begins with a thorough investigation of customer attributes to discover cus-tomers' needs. Developers note these needs, then determine the design's functional requirements (FRs) by answering the question, " What must this design do to satisfy our customers' needs? " Developers determine the answers and record the results as FRs in the left column of a design matrix. Across the top of the matrix, developers record the design parameters (DPs)Ñ physical solutions that satisfy each functional requirement. More than one design parameter may satisfy a particular function, but the information axiom will help determine the best solution. Developers may indicate a relationship between the functional requirement and the design parameter with an X in the matrix or with an equation. The matrix lets the developer check that each design parameter satisfies only one functional requirement. Developers decompose the design, working through each part to determine the subfunctional requirements and subdesign parameters of their previous design decisions until they've completed the entire design. The V-shaped diagram in Figure 1 shows the axiomatic development process for software. Some software development tools begin at the bottom of the V with module definition, giving little attention to top-down conceptual design. Axiomatic …