Structured Design (Design Goals)

- 1 min

Yesterday’s post introduced the idea of Structured Design. In this post, I will explain what I understand as the objectives of Structured Designed. Its main goal is good design and to achieve that goal, Structured Design focuses on the following characteristics of a system:

  1. Efficiency
  2. Reliability
  3. Maintainability
  4. Flexibility
  5. Generality
  6. Utility

Efficiency looks at how well resource management is performed in a system as well as how it can be improved. A system that manages its limited resources well is considered efficient.

Reliability focuses on how often a system which is considered repairable, will fail and the time between each failure. This is often described by the acronym MTBF (mean-time-between-failure). The third characteristic, Maintainability is to a certain extent related to Reliability. This characteristic describes the amount of time it takes to restore the system from an error. It is often referred to as MTTR (mean-time-to-repairs). This includes the time it takes to discover, analyse and fix the error. If the amount of time is relatively small, then the system is considered maintainable. Systems Availability is described by the following formula:

MTBF / (MTBF + MTTR)

Flexibility describes the ease in which a system can be extended and altered so that it can perform various tasks without changing the core theme of the system. Generality describes how generic a system can be. This goes in tandem with Flexibility since what is meant by generality is not how big a system should be and how many needs it should cover. What Generality means is that a system should be build from many smaller components that are easy to compose and decompose. If done correctly this means that you should be able to combine these components in many various ways and by doing so you achieve Generality.

Utility is the ease in which a system is available in the outside world and how easy it is to interact from a user’s perspective.

This concludes a brief description of the goals that Structured Design tries to achieve. I expect these objectives to be explored further as I progress further in the book.

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