Re: LSP Was: Mixing OO and DB

Bob Badour wrote:

> S Perryman wrote:

BB> In that case, I can only conclude you are an ignorant fool because
BB> D&D responded to L&W showing a computational model where Circle is
BB> indeed a subtype of Ellipse.

>> I can only conclude that you are an immense fool, for making claims
>> about what people can or cannot do, with no context info to base your
>> claim
>> on (someone with nominal intelligence would IMHO at the very least
>> challenge me to provide the demonstration - YMMV of course) .

> The Third Manifesto. Cure your ignorance and read it.

Immense fool + 1.
Have it (1st edition) . Read it. LOL.

Just to show this one is past its bedtime ...

Here is the apocrypthal Circle/Ellipse problem as would be specified in Liskov/Wing notions :

type Ellipse
{

     focusA ;
     focusB ;

     invariant : focusA > 0 AND focusB > 0

     focusA(A) ;
     post: focusA = A AND focusB = OLD.focusB

type Circle
{

     radius ;
     focusA ;
     focusB ;

     invariant : radius > 0
     invariant : radius = focusA
     invariant : focusA = focusB

     focusA(A) ;

     radius(R) ;
     post: radius = R

Circle is not a Liskov/Wing subtype of Ellipse.

Please feel free (if you have have said edition) to cite the pages in the D&D book (I have it by my side) that shows me how to define the above semantics, how the conflict is indicated/resolved etc.

Regards,
Steven Perryman Received on Fri Feb 22 2008 - 15:43:22 CET