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Re: [ontolog-forum] Semantic Web shortcomings [was Re:ANN: GoodRelations

To: "[ontolog-forum]" <ontolog-forum@xxxxxxxxxxxxxxxx>
From: "Len Yabloko" <lenya@xxxxxxxxxxxxx>
Date: Fri, 22 Aug 2008 20:55:26 +0000
Message-id: <W3769117891107581219438526@webmail40>
Christopher:    (01)

>> Now the fact that the "override" syntax gives rise to some bizarre
>> abuses is just the Goedel Corollary for Languages: "You can't allow
>> everything you want without allowing things you don't want."  And
>> "thinking in Java" is no better than "thinking in Fortran" -- it is
>> one level of abstraction below that required for the task of
>> software design.
>    (02)

I agree with Ed.    (03)

CS>While I can quite understand the short-term convenience of it, my
>problem with method overriding is that it torpedoes the Liskov
>Substitution Principle:  an instance of a subclass is no longer
>guaranteed to be an instance of the baseclass.  That's more than just
>a bizarre abuse -- it's an overthrow of polymorphism as well as
>    (04)

I don't agree. Identity and behavior are orthogonal aspects in OO. What matter 
is invariance with respect to specific operations. Preservation of identity or 
any other property can only be theoretically guarantied if you define category 
with morphisms. However, in practice invariance may be undecidable or hard to  
compute.    (05)

As of today OO is simply the closest we can come to enforcing LSP in general 
programming language.    (06)

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