What is "over-engineering" as applied to software?

terminology definition
Vlad Gudim picture Vlad Gudim · Jun 16, 2009 · Viewed 13.8k times · Source

I wonder what would be a good definition of term "over-engineering" as applied to software development. The expression seems to be used a lot during software design discussions often in conjunction with "excessive future-proofing" and it would be nice to nail down a more precise definition.

Answer

Michael Borgwardt picture Michael Borgwardt · Jun 16, 2009

Contrary to most answers, I do not believe that "presently unneeded functionality" is over-engineering; or it is the least problematic form.

Like you said, the worst kind of over-engineering is usually committed in the name of future-proofing and extensibility - and achieves the exact opposite:

  • Empty layers of abstraction that are at best unnecessary and at worst restrict you to a narrow, inefficient use of the underlying API.
  • Code littered with designated "extension points" such as protected methods or components acquired via abstract factories - which all turn out to be not quite what you actually need when you do have to extend the functionality.
  • Making everything configurable to "avoid hard-coding", with the effect that there's more (complex, failure-prone) application logic in configuration files than in source code.
  • Over-genericizing: instead of implementing the (technically uninteresting) functional spec, the developer builds a (technically interesting) "business rule engine" that "executes" the specs themselves as supplied by business users. The net result is an interpreter for a proprietary (scripting or domain-specific) language that is usually horribly designed, has no tool support and is so hard to use that no business user could ever work with it.

The truth is that the design that is most easily adapted to new and changing requirements (and is thus the most future-proof and extensible) is the design that is as simple as possible.

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