Subject Re: [firebird-support]Semantic Data Model was Derived tables
Author Ann W. Harrison
Carlos H. Cantu wrote:

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

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.