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/)
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