> -----Original Message-----
 > Behalf Of Mark Wonsil
...
 > The term relational comes from relational mathematics, i.e. set
 > theory. This is why there are union and intersection (join) functions.
...
 > ImageSQL *is* an SQL interface for Image, so Adam's point stands that
 > having an SQL interface does not a relational database make.

Excellent summary Mark.

Although SQL does not make a relational database, its development is 
closely linked, and I think that's why they are confused so often. The 
best explanation I've read of what a relational database is and how it 
was derived from set theory was published in a series of articles from 
Intelligent Enterprise magazine. Which starts at the link below

http://www.intelligententerprise.com/db_area/archives/1998/9810/feat4.jhtml

At the link below it finally gets into how Edgar F Cobb wanted to 
translate set theory in a computer language called Data Sublanguage 
Alpha. It was never implemented but it provide the basis for SQL.

http://www.intelligententerprise.com/db_area/archives/1999/991602/online2.jhtml

Jerry Finn
The Migration Factory
IBM Corporation
11400 Burnet Rd.
Austin, TX 78758
http://www-1.ibm.com/servers/eserver/migration/

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