zaterdag 10 april 2010

Datavault: an introduction

This year one of my goal is mastering Datavault modeling. In June i will be certifying myself in datavault. Dan Linstedt is coming to the Netherlands and will lecturing datavault modeling. The last day will be the day that a exam will be held. So in the coming weeks I’ll be blogging about the different aspects of datavault.

So what ‘s datavault all about? Well, it’s an alternative way of modeling. Other (data) model techniques are Boyce Codd normal Form and starmodelling (Kimbal). It’s a hybrid approach encompassing the best breed between3rd normal from and star schema. As Linsteds says: the design is flexible, scalable, consistent and adaptable to the needs of the enterprise. The model meets the needs of a Enterprise datawarehouse .

Below you can see an example of a complex datavault model, presented in a high level format:
This diagram shows a highly complex datavault datamodel. Looking at this diagram will give you a impression of a neuron network like the one created in brains. And yes it's influenced by that principle.
 
Mainly, there are three types of tables in the datavault design:
  • Satellites (Green) : Tables with attributes which changes at different rates (e.g. Customer name). Satellites provide the context for the business processes that are captured in hubs and links. This is mostly descriptive - and historical data and it’s used for descriptive information for the hubs or the links. You could compare this with TYPE II dimension of the Kimball methodology. It's function to provide context around the hub key.
  • Hubs (purple): These are the stand alone tables and they contain a list of the unique business keys. These keys identify the information domains used by the business. If the business were to lose the key they would lose the reference to the context, or surrounding information. Examples are customers (CustomerNumber), employees (Social security number), products (part_number), Sales orders (Orderid), purchase orders (PurchaseCode), Invoices (InvoiceNumber), etc.
  • Link (Black): These are the associatons or transactions between the business keys and it's used for relationships between hubs and links. Links are the physical representation of many-to-many 3NF relationship. The link representthe relationship between two or more business components (two or more business keys). This is an adaptation  of a many to many relationship in 3NF in order to resolve problems related to scalability and flexibility.
So this is it for now. The next blog's will be about how to turn a 3NF datamodel into a datavault model.

Greetz,
Hennie

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