Re: teaching relational basics to people, questions

From: Sampo Syreeni <>
Date: Sat, 21 Nov 2009 04:30:25 -0800 (PST)
Message-ID: <>

On Nov 20, 10:18 pm, (rpost) wrote:

> Doesn't this make it a bit hard to predict how long queries
> on time-valued domains may take?  The amount of time required for
> manipulating a value will greatly vary.  My guess is that why
> Date and Darwen rule it out for this reason.  Then again, Date
> defines the use of essentially arbitrary domains elsewhere.

I don't think so, because all of the logic would still revolve around similar comparison operations, on an identical number of endpoints. The only difference would be that in some cases there would be a less- -or-equal-to where a less-than was before, the numerical values used to store time ranges would have their lowest order bit used to denote the distinction between an open and a closed end point, and variable precision would be available at least at the conceptual level. At the physical one, it could always be implemented so that the complexity if bounded by the less precise of the compared values, or in fact limited to some fixed value at physical design time. And since one would have to have a bona fide range datatype, building in handling for infinite ranges would also be easy; that'd get rid of one of the most persistent reasons why people incorporate nulls into designs.

Received on Sat Nov 21 2009 - 13:30:25 CET

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