Don't repeat yourself

Do not repeat yourself (DRY, German about Do not repeat yourself, also known as a once and only once, dt about Once and only once ) is a principle that says to avoid redundancy or at least reduce.

Software Engineering

One field of application for the DRY principle is for example the programming.

Redundant existing information (eg code - duplication in source code) are difficult to maintain, because the consistency must be ensured between the duplicates. For systems that remain faithful to the DRY principle, however, changes need to be made in only one place.

While the DRY principle, the avoidance of redundancy to the goal that SPOT principle has to deal with ( intentional ) Redundancy the subject.

DRY is a fundamental principle in Andy Hunt and Dave Thomas's book The Pragmatic Programmer. In it, they propose to apply DRY for database descriptions, tests, build scripts, and even for documentation.