Re: Still struggling with history tables

On Jan 18, 2006, at 19:23 , Achilleus Mantzios wrote:

> Generally it is very hard to distinguish between two kind of UPDATES:
>
> a) UPDATEs that mean real data updates and they should be recorded
> to the history system.
> b) UPDATEs that are just false data entry, and they should mean
> just plain correction UPDATES, with no recording.
>
> This distinguishability is very important, otherwise someone would
> define a way to store historic data of changes to the historic data
> themselves, and so on.

Just a quick note:

Sometimes the term "valid-time" is used to talk about the interval of  
data validity, and tables that include valid-time intervals are  
sometimes referred to as "state tables". If you're interested in  
tracking when corrections are made, this is referred to as  
"transaction-time". Correcting the is sometimes called a  
"nonsequenced" update, because it's not correcting the sequence of  
validity: it's just a correction.

For more information, you can check out "Developing Time-Oriented  
Database Applications in SQL" by Richard Snodgrass (available as a  
free PDF download from his website[1]), or, for more theoretical  
information, "Temporal Data and the Relational Model" by CJ Date,  
Hugh Darwen, and Nikos Lorentzos.[2]

Michael Glaesemann
grzm myrealbox com

[1](http://www.cs.arizona.edu/people/rts/tdbbook.pdf)
[2](http://www.amazon.com/gp/product/1558608559/)