Lsp Quotes

LSP: The Liskov Substitution Principle Barbara Liskov’s famous definition of subtypes, from 1988. In short, this principle says that to build software systems from interchangeable parts, those parts must adhere to a contract that allows those parts to be substituted one for another.

The LSP makes clear that in OOD the ISA relationship pertains to behavior. Not intrinsic private behavior, but extrinsic public behavior; behavior that clients depend upon.