Dr. E.F.Codd must be rolling over in his grave. IBM, the IBM he worked for and developed the relational model at and for, is changing in its U2 database the definition of the relational database at the core – the first normal form rule. Specifically, that rule states that each column specifies one r none values for the attribute it defines/describes. None or one phone number not two. Now all DBAs and designers will know that the relational database structuring is built from 1stNormal through 5th or 6th Normal form. Many databases stop at 3rd or 4th. But to get to 4thNormal Form DBAs must have constructed a database that conforms to the previous rules.
Thus, C.J.Date notes in his book Database in Depth, if a [table] is in the (n+1)th normal form , then its certainly in the nth normal form. But certainly the converse is also true. So for the sake of simplicity and performance, IBMs U2 database sacrifices compliance with the full relational model.
Now I suspect, that the intentions are to perform these multi-value simplifications at the edges of the database. The core database tables would be defined in 3rd or 4th normal form and then for the complex networked or many-to-many relationships at the databases periphery would relax the rules and allow for multi-valued columns in some of these extreme tables. But I have only dabbled in the software, so who am I to say.
IBM is not kidding about this software and has developed a complete system around it:
Unidata – An extended relational database designed for embedding in vertical applications. UniData simplifies information management and query logic, providing more power for online high-transaction applications.
Universe – a second database which implements an extended relational database designed for embedding in vertical applications. This nested relational data model means intuitive data modeling and fewer resulting tables.
Redback – A scalable, object-based infrastructure for the U2 databases that includes an object-abstraction tool, allowing for development within a variety of technologies such as Java and ASP/JSP.
SystemBuilder – The Rapid Application Development (RAD) tool for IBM U2 databases, providing a structured process-based environment in which to create and maintain enterprise applications.
wIntergate – provides advanced terminal emulation application enhancement tool for IBM U2 databases and other MultiValue databases.
This line up of tools and databases provide connections not only to the major operating systems, Windows and Linux, but also to the major databases including IBMs own DB2 using some of the major database thorough fares such as ODBC, JDBC etc. In sum, U2 appears to be a continuing thrust that IBM is developing in the databae arena. Here are two resources that confirm that notions:
IBMs Direction and U2 Futures
An Assessment of the overall Multi-Value Market
A U2 System Presentation
Given XQuery and the resurrection of hierarchic databases (can an OOPsDBMS be far behind), this observer asks where is DBMS Magazine now that we really need it ? This tecnology looks not only feasible but seems to legitimize all the database stuff that string manip and regular expression jockeys like myself have been hiding away in big VARCHARs and CLOBs all along.