Re: The Practical Benefits of the Relational Model
From: Jan.Hidders <hidders_at_hcoss.uia.ac.be>
Date: 9 Oct 2002 10:36:23 +0200
Message-ID: <3da3ea87$1_at_news.uia.ac.be>
Date: 9 Oct 2002 10:36:23 +0200
Message-ID: <3da3ea87$1_at_news.uia.ac.be>
In article <bdf69bdf.0210080955.2b4af3d8_at_posting.google.com>,
Mikito Harakiri <mikharakiri_at_yahoo.com> wrote:
>hidders_at_hcoss.uia.ac.be (Jan.Hidders) wrote in message
>news:<3da1a630$1_at_news.uia.ac.be>...
>>
>> Symmetric? I can simulate the intersection with the difference. What is
>> the corresponding operator for the union?
>
>OK, let's introduce
>
>A -> B
>
>as a shorthand for complement(A minus B) [...] Therefore "->" is dual to
>minus, and the dual identity you were after is
>
>A union B = (A->B)->B
Nice. My complements. :-)
- Jan Hidders