Type Systems, Contract Systems, and IFC are three terms that I think are hard to distinguish using lay language.
Perhaps what you're pointing out is that there are many dynamic and static ways to verify assertions about programs? Certainly.
When programmers talk about "type systems" I think they tend to mean a static, sound, computable approach to verifying assertions about programs.
JIF is a _type system_, albeit not a unification-based one like ML. Moreover, the situations the GP is discussing seem like things that don't need the powerful type system of JIF. Something like ML could handle those situations with ease.
I think contract often takes one of two meanings among non-researchers. Either people are referring to assertions that are dynamically checked or they're referring to very expressive assertions (regardless of when they're checked).
These are all different ways of proving statements about programs.
Perhaps what you're pointing out is that there are many dynamic and static ways to verify assertions about programs? Certainly.
When programmers talk about "type systems" I think they tend to mean a static, sound, computable approach to verifying assertions about programs.
JIF is a _type system_, albeit not a unification-based one like ML. Moreover, the situations the GP is discussing seem like things that don't need the powerful type system of JIF. Something like ML could handle those situations with ease.
I think contract often takes one of two meanings among non-researchers. Either people are referring to assertions that are dynamically checked or they're referring to very expressive assertions (regardless of when they're checked).
These are all different ways of proving statements about programs.