Analysis Services 2005 defines for peak performance
Microsoft Analysis Services (MSAS) 2005 in SQL Server requires much work on a cube architect's part – work that was available for "free" in previous releases of the software. However, the new Analysis Services has considerably more flexibility and superior performance. To aggregate data correctly and to ensure the best possible performance, you must define appropriate attribute relationships and alter the values of certain attribute properties.
Purpose of attribute relationships
When you create a dimension based on a star-schema model (this implies that all attributes exist within a single dimension table), each attribute is related directly to the key attribute, but no other relationships exist between non-key attributes. If you use a snowflake schema and the dimension is based on two or more tables, then the key attribute from the main table is also related to the attribute used as the foreign key of the secondary table. In addition, the foreign key attribute is in turn related to the non-key attributes in the secondary table.