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.