Re: boolean datatype ... wtf?
Date: Thu, 30 Sep 2010 07:27:08 -0700 (PDT)
On Sep 30, 9:41 pm, David BL <davi..._at_iinet.net.au> wrote:
> Example : I have the means to measure (x,y) in a cave but not z. I
> want to record pH measurements taken on every stalagmite or
> stalactite. Relation is
> pHLevels(x,y, isStalagmite,pH)
> isStalagmite is part of the key.
My example is no good. Obviously it is easy to eliminate the 2-valued attribute in this case by introducing two relations
One can always remove a 2-valued attribute by using a pair of relvars (irrespective of whether it is part of the key). If this is done repeatedly the number of relvars grows exponentially.
In my example of recording a relation with 4 boolean attributes, one could in fact introduce 16 relvars that each have an empty heading and hold DEE or DUM.
So a "compelling example" would need a key involving perhaps 5 or more 2-valued attributes in the key such that splitting into many relvars is awkward.
Tricky... Received on Thu Sep 30 2010 - 09:27:08 CDT