Please don't take further discussion offline. This is fascinating, and as Date himself said "Theory is practical!". I believe this discussion is very relevant to what most of us do for a living. As an aside, one article of Date's I particularly enjoyed was "Tables with No Columns", Writings 1991-1994, p 45. The truth is, it DOES all start in the data model, and many of the uses we make of NULLs are due to insufficient attention paid to it. Every abstraction of the data model from "reality" requires a corresponding adjustment in the interpretation of the data. There is no getting around it. A person may say that it is worth it for performance or other reasons, but it is undeniable that an adjustment will be made by someone: the developer coding around it, or the user writing "notes" about it, or the customer who gets confused and frustrated, then goes elsewhere. I believe the most important point made was to model out all of the multiple-meaning NULL values in the data model that you possible can. It's hard work. It means going back to the users and asking them to define things they don't want to put forth the energy to define. However, if it's not done, the database will reflect neither "reality" nor the way the company wants to do business. As I said, someone, many people, will end up paying a price for modelers and developers straying from correct principles. Michael Milligan Oracle Certified Professional DBA PowerTrak DBA Field Group Ingenix, Inc. 2525 Lake Park Blvd. Salt Lake City, Utah 84120 wrk 801-982-3081 mbl 801-628-6058 michael.milligan@xxxxxxxxxxx -----Original Message----- From: Lex de Haan [mailto:lex.de.haan@xxxxxxxxxxxxxx] Sent: Friday, May 28, 2004 12:01 PM To: oracle-l@xxxxxxxxxxxxx Subject: RE: Useful Oracle books - C.J. Date theory vs. practicality thanks for the debate Dan -- same trick again ... (nice quoting exercise) Cheers, Lex. This e-mail, including attachments, may include confidential and/or proprietary information, and may be used only by the person or entity to which it is addressed. If the reader of this e-mail is not the intended recipient or his or her authorized agent, the reader is hereby notified that any dissemination, distribution or copying of this e-mail is prohibited. If you have received this e-mail in error, please notify the sender by replying to this message and delete this e-mail immediately. ---------------------------------------------------------------- Please see the official ORACLE-L FAQ: http://www.orafaq.com ---------------------------------------------------------------- To unsubscribe send email to: oracle-l-request@xxxxxxxxxxxxx put 'unsubscribe' in the subject line. -- Archives are at http://www.freelists.org/archives/oracle-l/ FAQ is at http://www.freelists.org/help/fom-serve/cache/1.html -----------------------------------------------------------------