Design Principles : Liskov Substitution Principle

LSP - Liskov Substitution Principle

What is wanted here is something like the following substitution property : If for
each object o1 of type S there is an object o2 of type T such that for all programs
P defined in terms of T the behavior of P is unchanged when o1 is substituted for o2
then S is a subtype of T.

RTTI usage
Design by contract