Re: Mixing OO and DB
From: Bob Badour <bbadour_at_pei.sympatico.ca>
Date: Fri, 22 Feb 2008 07:36:14 -0400
Message-ID: <47beb3af$0$4033$9a566e8b_at_news.aliant.net>
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> FORALL System S, FORALL Type T1,T2 IN S, the Liskov/Wing subtype
> definition certainly provides the means to evaluate the degree of
> substitutability possible for any given T1/T2.
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> I assume the above is what you meant by "type systems" (otherwise the
> analogy with normalisation is not a good one) . If I am mistaken, please
> feel free to correct me.
Date: Fri, 22 Feb 2008 07:36:14 -0400
Message-ID: <47beb3af$0$4033$9a566e8b_at_news.aliant.net>
S Perryman wrote:
>> S Perryman wrote:
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>>> Specifically : what "principle" is actually in effect here ??
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>>> That if some type T2 happens to be substitutable for T1 for one >>> particular context, that T2 should be a Liskov/Wing subtype of T1 ??
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>>> Hardly "value-added" (wrt to the Liskov/Wing definitions) is it.
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>> Actually, the principle provides a method to evaluate type systems >> just as normalization provides a method to evaluate logical designs.
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> FORALL System S, FORALL Type T1,T2 IN S, the Liskov/Wing subtype
> definition certainly provides the means to evaluate the degree of
> substitutability possible for any given T1/T2.
>
> I assume the above is what you meant by "type systems" (otherwise the
> analogy with normalisation is not a good one) . If I am mistaken, please
> feel free to correct me.
You left the part about subtypes out, but otherwise, that will do as the start of a pseudo-english description of an algorithm for evaluating a system of type systems. Received on Fri Feb 22 2008 - 12:36:14 CET