Re: boolean datatype ... wtf?

From: David BL <davidbl_at_iinet.net.au>
Date: Wed, 29 Sep 2010 23:03:22 -0700 (PDT)
Message-ID: <bba9fa59-d83d-4467-8514-acd82dc09ad4_at_k17g2000prf.googlegroups.com>



On Sep 29, 8:48 pm, Erwin <e.sm..._at_myonline.be> wrote:

> the RM already has a way for
> representing truth information (as the presence/absence of some tuple
> in some relvar with some particular predicate), and as a consequence
> the type BOOLEAN (_WITHIN DATABASE RELVARS_) must be considered
> redundant and unnecessary.

What if I want to record a base relation like the following?

a b c d



F F F F
F F T T
F T F T
T F F F
T F T T

These boolean attributes can't be eliminated in the manner you suggest.

On another note, I can easily imagine applications with boolean attributes that cannot be regarded as derived or calculated from other information recorded in the database. E.g. soft cover versus hard cover, read versus unread, fiction versus non-fiction for a book.

I agree that one typically has the option of using more relvars to record these attributes instead as the presence/absence of some tuple. However I think it won't be possible when these boolean attributes form part of the primary key. I can imagine applications where we don't have convenient and simple identifiers for entities, and they end up being uniquely identified by a large number of attributes, and I would have thought there could easily be cases where some of the attributes in the key are boolean. Received on Thu Sep 30 2010 - 01:03:22 CDT

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