Abstraction principle (computer programming)

In software engineering and programming language theory, the abstraction principle (or the principle of abstraction) is a basic dictum that aims to reduce duplication of information in a program (usually with emphasis on code duplication) whenever practical by making use of abstractions provided by the programming language or software libraries. The principle is sometimes stated as a recommendation to the programmer, but sometimes stated as a requirement of the programming language, assuming it is self-understood why abstractions are desirable to use. The origins of the principle are uncertain; it has been reinvented a number of times, sometimes under a different name, with slight variations.

When read as recommendation to the programmer, the abstraction principle can be generalized as the "don't repeat yourself" principle, which recommends avoiding the duplication of information in general, and also avoiding the duplication of human effort involved in the software development process.

As a recommendation to the programmer, in its formulation by Benjamin C. Pierce in Types and Programming Languages (2002), the abstraction principle reads (emphasis in original):

As a requirement of the programming language, in its formulation by David A. Schmidt in The structure of typed programming languages (1994), the abstraction principle reads:.

Under this very name, the abstraction principle appears into a long list of books. Here we give a necessarily incomplete list, together with the formulation if it is succinct:

The principle plays a central role in design patterns in object-oriented programming, although most writings on that topic do not give a name to the principle. The influential book by the Gang of Four, states: "The focus here is encapsulating the concept that varies, a theme of many design patterns." This statement has been rephrased by other authors as "Find what varies and encapsulate it."

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