Real World Instrumentation with Python

Designing the Software

Now that you have some functional requirements, in whatever format, it’s time to think about designing the software to meet those requirements. How much latitude is available in the design will depend on how detailed the functional requirements happen to be. If they are extremely detailed, you won’t have as much leeway as with a loose set of functional requirements.

The Software Design Description

In Figure 8-4 the last thing in line before the software is the software design description, also known as the SDD. The SDD is, in effect, a set of low-level implementation requirements. Often the SDD is written in a more narrative form than the functional-level requirements. It typically contains things like definitions of return code values, flowcharts, block diagrams, inheritance diagrams, message sequence charts, and so on. The SDD is the theory of operation document for the system to be built, and it should contain enough details such that a programmer can translate it directly into working code. Typically, the SDD is organized along the same lines as the software. In other words, there might be a section describing data acquisition, another dealing with data processing, one that describes the user interface, and so on. A comprehensive SDD may also contain one or more introductory overview sections that reiterate the SOW in a more technical context and lay the groundwork for the detailed descriptions in subsequent sections of the document.

For small projects an ...