Representation Independence and Data Abstraction (Summary) (NOT KNOWN IF TALK GIVEN BECAUSE AUTHOR HAS LEFT AT&T)

One purpose of type checking in programming languages is to guarantee a degree of "representation independence:" programs should not depend on the way stacks are represented, only on the behavior of stacks with respect to push and pop operations. In languages with abstract data type declarations, representation independence should hold for user-defined types as well as the built-in types.