Re: Network databases

On 14 Jan 2005 14:25:08 -0800, lynn_at_garlic.com wrote:

>Alfredo Novoa wrote:
>> But DB2 is not a relational DBMS.
>
>here is one reference:
>Are SQL Server, DB2 and Oracle really relational?
>http://www.handels.gu.se/epc/archive/00002948/

But a bad reference.

Here is a better one:

http://www.aw-bc.com/catalog/academic/product/0,4096,0321197844,00.html

>http://expertanswercenter.techtarget.com/eac/knowledgebaseAnswer/0,295199,sid63_gci976464,00.html

Plain wrong. What an "expert"!

>http://en.wikipedia.org/wiki/RDBMS

<quote>

There is some disagreement about what can or cannot be called a "relational" DBMS.

The most popular definition of a RDBMS is relatively imprecise; some argue that merely presenting a view of data as a collection of rows and columns is sufficient to qualify as a RDBMS. Typically, products that qualify as a RDBMS under this interpretation implement some of Codd's 12 rules, but most popular database systems do not support them all.

Popular commercial DBMSs sold as RDBMSs include Oracle, Microsoft SQL Server, Sybase SQL Server, IBM's DB2, and Microsoft Access. MySQL, PostgreSQL and Firebird are free RDBMSs.

A second school of thought argues that if a database does not implement all of Codd's rules, it is not relational. This view, shared by many theorists and other strict adherents to Codd's principles, would disqualify many database systems from being considered "truly relational". In fact, any database that uses the Structured Query Language (SQL) to access and modify data is not an RDBMS under this definition. Advocates of this philosophy refer to systems that follow some but not all of the rules as Pseudo-Relational Database Management Systems (PRDBMS). For clarification, they often refer to DBMSs that do follow all of the rules Truly-Relational Database Management Systems (TRDBMS). </quote>

I am a member of the second school :)

But it is not very correct. Codd's rules are outdated since a long time ago. We can find a modern interpretation of the Relational Model in "The Third Manifesto".

http://www.thethirdmanifesto.com

Regards Received on Sun Jan 16 2005 - 00:35:51 CET