Re: LSP Was: Mixing OO and DB

"Daniel T." <daniel_t_at_earthlink.net> writes:
>I'm not sure what you mean by the above.

  The text often quoted as »the LSP« is

      "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 ."

  This text does not /explicitly/ mention »contract« or   »specification« (it does not contain theses words nor any   synonyms).

  It is true, that it might implicitly refer to a specification   or that it stems from a context referring explicitly to a   contract.

>I think the phrase that is often quoted from the Liskov papers is
>unfortunate because it says nothing of *her* solution to the problem. A
>better quote from her '99 paper is:
>
> "the subtype ought to preserve any properties that can be proved
> about the supertype."

  Yes. See also

http://www.cs.cmu.edu/~wing/publications/LiskovWing94.pdf http://citeseer.ist.psu.edu/liskov94behavioral.html Received on Sat Feb 23 2008 - 17:46:44 CET