Re: On formal HAS-A definition

"Bob Badour" <bbadour_at_pei.sympatico.ca> wrote in message news:4be61731$0$12462$9a566e8b_at_news.aliant.net...
> Mr. Scott wrote:
>
>> "Bob Badour" <bbadour_at_pei.sympatico.ca> wrote in message
>> news:4be5b09f$0$26945$9a566e8b_at_news.aliant.net...
>>
>>>Mr. Scott wrote:
>>>
>>>
>>>>"Bob Badour" <bbadour_at_pei.sympatico.ca> wrote in message
>>>>news:4be59bfa$0$12451$9a566e8b_at_news.aliant.net...
>>>>
>>>>
>>>>>Mr. Scott wrote:
>>>>>
>>>>>
>>>>>
>>>>>>"Mr. Scott" <do_not_reply_at_noone.com> wrote in message
>>>>>>news:Atqdnbh1eNZ_YX7WnZ2dnUVZ_g-dnZ2d_at_giganews.com...
>>>>>>
>>>>>>
>>>>>>
>>>>>>>"Tegiri Nenashi" <tegirinenashi_at_gmail.com> wrote in message
>>>>>>>news:0b0623a8-7a8c-476b-8de2-78c31a36ab17_at_f17g2000pra.googlegroups.com...
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>>Again, I didn't research literature, but here is my shot: the HAS-A
>>>>>>>>is
>>>>>>>>an inclusion dependency. Example:
>>>>>>>>
>>>>>>>>Dept = [DeptNo DeptName]
>>>>>>>> 10 Accounting
>>>>>>>> 20 Research
>>>>>>>>;
>>>>>>>>
>>>>>>>>Emp = [DeptNo EmpName]
>>>>>>>> 10 King
>>>>>>>> 10 Smith
>>>>>>>>;
>>>>>>>>
>>>>>>>>Formally:
>>>>>>>>
>>>>>>>>Emp v (Dept ^ []) < Dept v (Emp ^ []).
>>>>>>>>
>>>>>>>>I suppose HAS-A shares many unconvenient properties with set
>>>>>>>>membership, for example, it is not transitive. Consider
>>>>>>>>
>>>>>>>>Accounts = [EmpName Institution]
>>>>>>>> Smith BoFA
>>>>>>>> Smith WellsFargo
>>>>>>>>;
>>>>>>>>
>>>>>>>>the it is not the case that "Dept HAS-A Accounts". Again, the naming
>>>>>>>>problem raises its ugly head: why would the first attributes be
>>>>>>>>called
>>>>>>>>"EmpName" rather than "PersonName"?
>>>>>>>>
>>>>>>>>More important: is this correct formalization? Specifically,
>>>>>>>>shouldn't
>>>>>>>>functional dependency
>>>>>>>>
>>>>>>>>Dept # DeptNo < Dept # DeptName
>>>>>>>>
>>>>>>>>be a part of HAS-A constraint definition?
>>>>>>>
>>>>>>>I don't think nontrivial functional dependencies have any bearing on
>>>>>>>whether or not there is a 'has-a' relationship; instead, it is the
>>>>>>>juxtaposition of attributes in a relation scheme under the convention
>>>>>>>that it is not just components that are significant but also tuples.
>>>>>>>If there is a mapping from tuples into the domain of discourse, then
>>>>>>>it follows that the components of a tuple map to parts of the whole
>>>>>>>that the tuple maps to.
>>>>>>
>>>>>>One could argue that a trivial functional dependency from the superkey
>>>>>>that consists of the entire heading of a relation to any proper subset
>>>>>>of the heading specifies a 'has-a' relationship.
>>>>>>
>>>>>>I should also point out that because 'has-a' relationships are in
>>>>>>essence part-whole relationships, that they are transitive. For
>>>>>>example, cars have tires; tires have rims; therefore, cars have rims.
>>>>>
>>>>>Except that not all cars have tires--some are on blocks. We could just
>>>>>as legitimately say that all tires have cars.
>>>>
>>>>Without tires, there is no car, but it is not necessary for a car's
>>>>tires to be physically attached for them to be part of the car.
>>>
>>>That's absurd. A car without tires remains a car just as an amputee
>>>remains a human being.
>>
>> A vehicle that never has had nor can have tires is not a car. If the car
>> is on blocks, then even though its tires have been removed, they're still
>> the car's tires. A car that is still on the assembly line also has
>> tires--even if they haven't yet been ordered. If someone were to ask,
>> "Where are that car's tires?" It would be really strange to hear an
>> answer like "there aren't any." Instead, one might say, "they've been
>> put on another car," or "they're on order," or "they've been stolen."
>>
>> An amputee's limb is still his limb even though it has been removed, but
>> even so, having four limbs isn't essential to being a human, whereas
>> having tires is essential to being a car.
>
> You are a complete fucking idiot.

Plonk! Received on Sun May 09 2010 - 04:13:30 CEST