But even without "leaks" as you describe them, there are still semantic leaks.  Just because S implements push: and pop, doesn't mean that S is actually going to act like a stack.  The fact that it has the proper selectors is only the beginning.

If you want *really* strong guarantees for your code, you need to get into program proofs.  Developing the state of programming proofs to where they are practical, would truly be a wonderful thing.  But it doesn't sound like what you present system is aimed towards.


Lex


"Peter Smet" <peter.smet at flinders.edu.au> wrote:
> Charles,
> 
> Maybe I am looking at interfaces from the wrong angle. I see an Interface as
> a kind of contract. If an Object implements an interface, you can make lots
> of otherwise dangerous assumptions about what messages it understands.
> Similar to IDL or Types (I know, that word makes Smalltalkers cringe). If
> Distributed Objects are to be the next big thing, how will you talk to them?
> Discovering an Interface is a good way. As I have explained, the current
> Interfaces are 'leaky' in that an Object can have Interface A, you can send
> it an Interface A message, but the object will not understand it. I gave an
> example of this in my previous post -
> 
> >>To truly reason
> >>about Interfaces it is not enough to treat them as a bunch of selectors.
> To
> >>me, the function of an Interface is as a prerequisite for communcation
> >>between objects. In its present form, objects with compatible interfaces
> may
> >>NOT be able to communicate.
> >>