An Open Source database modeling technique built on the premise that the environment surrounding a data warehouse is constantly changing is called anchor modeling. A large change on the outside of the model will result in a small change inside. The technique is easy to use and understand because of the natural conecpts of objects. It is based on the sixth normal form, which avoids many of the pitfalls associated with traditional database modeling. The technique is modular and supports separation of concerns. If you start small with prototyping, you can grow into an enterprise data warehouse without having to redo previous work.

A generic modeling approach is also suitable for other types of systems, even though its origins were in data warehousing. The existing model has an independent non-destructive extension for every change. All current applications will not be affected. All versions of an application can be run against the same evolving database, and changes in the input to and output from the database can be handled asynchronously. The database model is still a subset of the anchor model.

A fixed model can only survive for a short period of time. At some point a change will occur that could not have been foreseen, and if the initial effort was to create an all-inclusive model you may now be facing dramatic alterations to cope with the new situation. It’s assumed that perfect predictions never can be made. Database models should be changed when they are built. They need to last in an ever changing environment.