Path: utzoo!utgpu!jarvis.csri.toronto.edu!rutgers!gatech!purdue!mailrus!ncar!boulder!sunybcs!canisius!elgie
From: elgie@canisius.UUCP (Bill Elgie)
Newsgroups: comp.databases
Subject: Re: Relational Model
Keywords: relational empirical support
Message-ID: <2409@canisius.UUCP>
Date: 25 Jul 89 04:20:22 GMT
References: <AYknCfy00WB28IU6sk@andrew.cmu.edu> <18886@sequent.UUCP> <19101@sequent.UUCP>
Organization: Canisius College, Buffalo N.Y. 14208
Lines: 48

In article <19101@sequent.UUCP>, normb@sequent.UUCP (Norm Browne) writes:
> 
> One of the relational model's [supposed] major advantages is that it has a
> THEORETICAL underpinning (mathematical set theory).  This is why it is
> ``superior'' to the Codasyl or hierarchical models.  Does set theory really
> reflect the real world?[1]  Is it more intuitive?  
> 
  I do not understand this supposition, that a database "model" is supposed
  to "reflect the real world".  Why ?   Given the broad range of applications
  for which database systems have been implemented, it seems awfully simplis-
  tic to me to make such a generalization about any conceivable database 
  model.  Is there ANY model of ANY kind (dbms, economic, whatever) that can
  be said to "reflect the real world" ?  Or simply certain instances/subsets
  of it ?

  A given database application must "reflect the real world" of the particular
  organization, or project, or whatever, for which that application was devel-
  oped (if that database is to be successful);

  the individual designing the database must structure it so that it does, in
  fact, reflect the organization, etc, faithfully;

  in my opinion:

    it is easier to do so using a database adhering to the CODASYL or hierar-
    chical model if the application model happens to fit AND if the applica-
    tion model remains static;

    it is easier to do so using a relational model dbms otherwise, precisely
    because the relational model is closest to being a "clean slate" by not
    trying to "reflect the real world".  The relevance of a set theory under-
    pinning is NOT that it provides a view of a human organizational structure
    but that it provides a view of organized computer data which is replicable,
    robust, and, at the same time, flexible.  It is up to the implementor of
    an application to establish a "reflection".  In my opinion, this is more
    difficult to do and maintain (the real world tends to be dynamic) using
    dbms's based on models which attempt to mix data organization with human
    organization.

> Normalization and E-R can be applied to network and hierarchical DBs so
> they also do not differentiate relational DBs.
> 
  Much of what is considered to constitute the "relational data model" applies
  to (or should apply) to the design of a database for most applications: it
  is good S.O.P.


   greg pavlov (under borrowed account), fstrf, amherst, ny