--- Bill Walton <[EMAIL PROTECTED]> wrote: > > Exactly. Without the intervening layer introduced by the Relational > Model, > a search is intimately and inextricably bound to the underlying > structure of > the data to be searched. Change the structure of the data and you > have to > change the programs that access it. That is the problem, along with > a host > of related ones, that Codd set out to solve. The Relational Model > solved > that problem and did so in a mathematically provable way. The > "mathematically provable" part is what you found so enlightening on > the > Wikipedia ;-) > > Best regards, > Bill > > Kevin >
I like to think of the relational model as playing a role in database theory analogous to that of Turing machines or lambda calculus in language theory. Turing machines may be particularly efficient ways to implement programming languages (or computers), but they are formal mathematical models we can reason about. The same goes for lambda calculus, of course, but the first functional languages were about 100 times slower than Fortran or assembly language. That's changed considerably, and today the best compilers for functional languages achieve about 70% of the performance of C. Similarly, relational databases often get a bad rap in the MUMPS community because they are perceived as inherently slow. But that is a category error: an *implementation* can be slow, but a logical mode is neither fast nor slow, it is a formal framework for *reasoning* about databases and database queries. I'll leave it to others to argue about the state of the art in design of (concrete) relational database systems, but the relational model is a mathematical framework like a Turing machine. It should be thought of as a theoretical tool. === Gregory Woodhouse <[EMAIL PROTECTED]> "It is foolish to answer a question that you do not understand." --G. Polya ("How to Solve It") ------------------------------------------------------- This SF.Net email is sponsored by xPML, a groundbreaking scripting language that extends applications into web and mobile media. Attend the live webcast and join the prime developer group breaking into this new coding territory! http://sel.as-us.falkag.net/sel?cmd=lnk&kid=110944&bid=241720&dat=121642 _______________________________________________ Hardhats-members mailing list Hardhats-members@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/hardhats-members