Anchor Modeling

Did you know that some of the earliest prerequisites for data warehousing were set over 2500 years ago. It is called an anchor model since the anchors tie down a number of attributes (see picture above). All EER-diagrams have been made with Graphviz. All cats are drawn by the author, Lars Rönnbäck. 2 2 You can never step into the same river twice. 2 The great greek philosopher Heraclitus said " You can never step into the same river twice ". What he meant by that is that everything is changing. The next time you step into the river other waters are flowing by. Likewise the environment surrounding a data warehouse is in constant change and whenever you revisit them you have to adapt to these changes. Image painted by Henrik ter Bruggen courtsey of Wikipedia Commons (public domain). • A future-proof data warehouse must at least fulfill: – Value – Maintainability – Usability – Performance – Flexibility Fail in one and there will be consequences Value – most important, even a very poorly designed data warehouse can survive as long as it is providing good business value. If you fail in providing value, the warehouse will be viewed as a money sink and may be cancelled altogether. Maintainability – you should be able to answer the question: How is the warehouse feeling today? Could be healthy, could be ill! Detect trends, e g in loading times. Usability – must be simple and accessible to the end users. Should not take a university degree in computer science to get the information you want. Performance – demands may vary depending on the user. Analysts may be satisfied waiting 10 minutes for a query, while users looking at dynamical reports may require sub second response times. Finally flexibility, which will be the main subject of todays presentation. • Resilient to changes in the environment surrounding the data warehouse • The model simplifies – historization – null-handling – orphans – separation of concerns – prototyping • Achieves performance gains A large change outside the data warehouse should result in a small change within. Anchor modeling is nothing new. The ideas and theories have been around since the 70ies, but has only recently been adopted by us and used in practice. 5 5 Background – 6NF • A table is in sixth normal form if and only if it satisfies no non-trivial join dependencies …