zondag 25 april 2010

Datavault : Identifying the Satellites

In the first parts (part 1 and part 2) i wrote a small introduction about Datavault and identified the Hubs during a small analysis. Today i'm gonna identify the Links in the 3NF model of the AdventureWorksLT database.

So what are links, again? Links tie two or more hubs together. Links represent the relationship between two or more business elements. These are usually the business events or transactions. Each link has its own surrogate key, the keys from the hubs, a load date time stamp and a record source.

Below you can see the diagram in which i've identified the link tables:

How can you identify the link tables. Link tables can be identified by looking at typical transaction tables and many - to -  many tables (facts). Secondly, Lindstedt states that any table that doesn't  have a respective business key becomes a good link identity. First, lets start with identifying the easy link tables (many to many)

  • Salesorderheader: Many to Many table.
  • Salesorderdetail: Many to Many table.
  • CustomerAddress: Many to many table.
  • ProductModelProductDescription: Many to Many table.
  • Product: Many to many table
So there 1 more link table left:
  • The first one is the recursive Product Category table. This table has also a prent child relationship and therefore a link table is neccessary.
So that's it for now. Next time the satellites.


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