Re: Nested Sets vs. Nested Intervals
Date: 9 Nov 2005 09:23:44 -0800
> Calling Codd's work a myth is cute, but can you offer any technical
> argument in favour of "graph-based systems" in addtion to what has been
> rehashed on this newsgroup many times and besides "I say so" ?
I don't recall the arguments in Codd's original article of 1970 or so. Maybe I'll take a relook next time I stop by the University library. Anyway the following holds.
Some semantic domains are better modelled with graphs and trees than with relations. The idioms for trees and graphs in SQL is extremely convoluted to say the least (the word "pathetic" comes to mind). The original problem in this thread is an concrete example.
Relational star people themselves recognized shortcomings of the relational theory for semantic modelling. This was a major factor in the creation of the Entity-Relationship model. And guess what: the E-R is a graph-based model. (Not to mention UML class diagrams, but I know what you'll say: these are for programs, not data.)
There's graph-based and graph-based. As you I also don't subscribe to the socalled "hierarchical" and "network" models as they are often presented in relational circles. They seem to be a heritage of Codasyl and alike systems of the 1960's. Fortunately others kept researching and have come up with much better graph-based models e.g. Resource Description Framework and even XML. Received on Wed Nov 09 2005 - 18:23:44 CET