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Re: How to store temporal info?

From: Lennart Jonsson <lelle2_at_bonetmail.com>
Date: Mon, 03 Mar 2003 19:38:05 +0100
Message-ID: <b407bq$1qd9l2$1@ID-167942.news.dfncis.de>


On Mon, 03 Mar 2003 14:18:49 +0000, John Gilson wrote:

[...]
>
> I would second the use of the latest-representable date, instead of NULL, to
> represent a valid time that's currently valid.
>
> The Snodgrass book is quite good and complete. You might also be interested
> in the latest by Date and Darwen, "Temporal Data and the Relational Model",
> which you can find out more about at www.thethirdmanifesto.com.
>

They had a nice summary on the site (Temporal Data and the Relational Model, Hugh Darwen's summary of the book). I only had a glimpse at it, but that alone gave me ideas I think I will ba able to use. To summarise, A Resource belongs to exactly one ResourceCategory at a time. Hence the relation:

        *Resource, *ResourceCategory, *Since

will serve my needs. The problem is then reduced to finding the max(since) <= resulttime for a given resource. Besides from not having to deal with nulls (or infinite date) in todate, it also eliminates the need of "checking for overlaps" at the time of insert

Anyhow, thanx to both of you for your comments

/Lennart

[...] Received on Mon Mar 03 2003 - 12:38:05 CST

Original text of this message

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