Carlos H. Cantu wrote:

>
> http://www.firebirdnews.org/?p=3830

Mike Hammer and Dennis McLeod called this the "Semantic Data
Model" in their 1978 paper.

http://portal.acm.org/citation.cfm?id=509264

Jim's been interested in it ever since and has included it in
his latest database. The trick is finding an efficient way
to model several variant of a table. Hint: neither joins nor
unions makes the cut.


Cheers,

Ann