Codd’s Twelve Rules

E.F. Codd’s 12 rules (well, thirteen):

Twelve rules are cited below as part of a test to determine whether a product that is claimed to be fully relational is actually so. Use of the term “fully relational” in this report is slightly more stringent than in my Turing paper (written in 1981). This is partly because vendors in their ads and manuals have translated the term “minimally relational” to “fully relational” and partly because in this report, we are dealing with relational DBMS and not relational systems in general, which would include mere query-reporting systems.

However, the 12 rules tend to explain why full support of the relational model is in the users’ interest. No new requirements are added to the relational model. A grading scheme is later defined and used to measure the degree of fidelity to the relational model.

This particular article seems less important thirty years later, but it was vital in the early days of relational systems to understanding what, precisely, a relational database management system ought to do and—just as importantly—what it ought not do.  It wasn’t enough to slap SQL on top of a hierarchical database platform and call it relational.

Related Posts

Building Data Dictionaries

Caitlin Hudon shares some great advice on building data dictionaries: The best defense I’ve found against relying on an oral history is creating a written one. Enter the data dictionary. A data dictionary is a “centralized repository of information about data such as meaning, relationships to other data, origin, usage, and format”, and provides us with a […]

Read More

Master Data Services No Longer Uses Silverlight

Niko Neugebauer is happy about an update to Master Data Services in SQL Server 2019: Before we continue, let me ask you one question, have you heard about Silverlight? Or in other words, and with a kind of evil voice “DID YOU EVER INSTALLED SILVERLIGHT ON A PRODUCTION SERVER”?. If you have worked with MDS oh […]

Read More

Categories

May 2016
MTWTFSS
« Apr Jun »
 1
2345678
9101112131415
16171819202122
23242526272829
3031