Liskov Substitution Principle
A software design principle holding that objects of a superclass should be replaceable with objects of a subclass without altering the correctness of the program.
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Origin
Introduced by computer scientist Barbara Liskov in her 1987 keynote "Data Abstraction and Hierarchy" at the OOPSLA conference. Liskov and Jeannette Wing later formalized the idea in a 1994 paper on behavioral subtyping. Robert C. Martin gave it its current name when he included it among his SOLID design principles.
Updated February 22, 2026