Re: Interpretation of Relations
From: paul c <toledobythesea_at_oohay.ac>
Date: Sat, 20 Jan 2007 12:38:13 GMT
Message-ID: <V2osh.723797$1T2.394965_at_pd7urf2no>
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Date: Sat, 20 Jan 2007 12:38:13 GMT
Message-ID: <V2osh.723797$1T2.394965_at_pd7urf2no>
Joe Thurbon wrote:
> On 2007-01-19 21:22:02 +1000, paul c <toledobythesea_at_oohay.ac> said:
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>> Joe Thurbon wrote:
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>>>
>>> Relation R_People = <<D_People>: {{Joe}}>
>>> Relation R_Hair Colour = <<D_People X D_Hair>: {{Joe, Blond}}>
>>>
>>> (The bit in the <> is the relation header, the subsequent sets are
>>> the relation body).
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>>>
>>>
>>> R_Hair Colour: <<D_People X D_Hair>: {}>
>>>
>>> indicates that I don't know the colour of Joe's hair. It really means
>>>
>>> NOT Joes hair is Red
>>> NOT Joes hair is Blond
>>>
>>> Is this right? ...
> ...
Sorry, reading too quickly, I didn't notice that you had re-stated R_Hair Colour without the {Joe, Blond} tuple. So, yes I think it is right and the complement of your second version would have two rows/tuples.
p Received on Sat Jan 20 2007 - 13:38:13 CET