Code And Cocktails

Software Life Span

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(Cross posted to the Cyrus Innovation Blog)

Software maintenance is an extremely important but highly neglected activity.

…says Boehm1 in the midst of a long paper about the current and possible future state of Software Engineering at the end of 1976. I think this statement is just as true today as it was almost 40 years ago when Boehm wrote it.

Boehm defines Software Maintenance as “the process of modifying existing operational software while leaving its primary functions intact.” (which sounds a lot like what we now call Refactoring). He states the Maintenance has three main ‘functions’ which imply certain needs:

  • Understanding the existing software: This implies the need for…well-structured and well-formatted code
  • Modifying the existing software: This implies the need for software, …, and data structures which are easy to expand and which minimize side effects of changes…
  • Revalidating the modified software: This implies the need for software structures which facilitate selective retest, and aids for making retest more thorough and efficient.

We have the tools today to do these things. They are things like modular design, the SOLID principles, and TDD. We have learned ways to write well-structured code which minimize side effects of changes and which facilitate retest. We’ve written languages and libraries which help us do these things.

But yet maintenance is still a problem.

Perhaps we as an industry are focusing only on the “cool” stuff. Or believe/hope that “someone else” will maintain it. Or focusing on immediate customer need and not considering long term needs. The customer themselves may not consider the long term costs.

As professionals we need to consider the life-span of the code we are writing, and write it accordingly. If a civil engineer is asked to build a bridge that need only last for a single crossing it will be quite different than if the bridge needed to last for decades (or longer). We need to think in same ways.

Currently we often write software as if it only needs to work for today. No thought is given to tomorrow.

We have the tools to write software that can live as long as it needs to. But we need to treat the life-span as a requirement.


  1. Boehm, B. W. “Software Engineering” Classics in Software Engineering. Ed. Edward Nash Yourdon. New York: YOURDON Press, 1979. pp325-361. Print. 

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