Creating Your First Multidimensional Cube - Getting Started with SQL Server 2012 Cube Development - page 49

Understanding the data source view
The data source view is a very important concept in Analysis Services. You can think
of it as an abstraction layer between the relational database and the multidimension-
al cube. You have the ability to define objects that do not exist in the database. The
data source view provides a logical view of the database, so to Analysis Services, the
objects appear to exist in the database. This includes new tables, columns, and even
referential integrity or relationships between objects.
Tip
In many cases you do not define referential integrity down in the database layer
when you work with data warehouses. The reason for this is that loading of the
data is much easier without them. If you have defined foreign keys and primary
keys, you need to ensure that you always load your objects in the correct order.
If your data warehouse does not contain referential integrity, it has to be created
in the data source view.
You can also add calculations to existing tables. They could be simple concatenations
of existing columns or contain more complex logic. Sometimes there is an advantage
to add the calculations to the data source view as you will actually store the informa-
tioninthemultidimensionalstore.However,youalsoneedtobearinmindthatthecal-
culations will be executed as part of the process step by the underlying data source,
so it may cause an additional burden on the source system if they are very complex.
When you create your data source view you can either bind to tables or views that
exist in the data warehouse itself; or you can create a named query. Think of a named
query as a view down in the database but it only resides in Analysis Services. The
reason why you would not just create a view could be that you are working against a
database where you are not allowed to change or add any objects. Also remember,
Analysis Services work against not just a SQL Server, it could also be that you are
working against a source that does not have the concepts of views.
As you understand, this gives you a lot of flexibility and allows you to create a multidi-
mensional model on top of a database schema that may be in the 3NF form.