Softwarew Engineering-Component Level Design


Component-level design, also called procedural design, occurs after data, architectural, and interface designs have been established. The intent is to translate the design model into operational software. But the level of abstraction of the existing design model is relatively high, and the abstraction level of the operational program is low. The translation can be challenging, opening the door to the introduction of subtle errors that are difficult to find and correct in later stages of the software process. In a famous lecture, Edsgar Dijkstra, a major contributor to our understanding of design, stated :

Software seems to be different from many other products, where as a rule higher quality implies a higher price. Those who want really reliable software will discover that they must find a means of avoiding the majority of bugs to start with, and as a result, the programming process will become cheaper . . . effective programmers . . . should not waste their time debugging—they should not introduce bugs to start
with.

Although these words were spoken many years ago, they remain true today. When the design model is translated into source code, we must follow a set of design principles that not only perform the translation but also do not “introduce bugs to start with.”

It is possible to represent the component-level design using a programming language. In essence, the program is created using the design model as a guide. An alternative approach is to represent the procedural design using some intermediate (e.g., graphical, tabular, or text-based) representation that can be translated easily into source code. Regardless of the mechanism that is used to represent the componentlevel design, the data structures, interfaces, and algorithms defined should conform to a variety of well-established procedural design guidelines that help us to avoid errors as the procedural design evolves.
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