One of the features that has been expanded upon in SSAS 2008 when compared to SSAS 2005 is the concept of attribute relationships. In SSAS 2008 there ia Attribute realtionships editior which is GUI based. It allows the developer to explicity to define the realtionships between the diferent attributes in a dimension. This concept is very important to be understood while building a dimension as this has an effect on the performance of the cube. As per MSDN: attribute relationships offer the following performance advantages:
An attribute relationship provides the following advantages:
• Reduces the amount of memory needed for dimension processing. This speeds up dimension, partition, and query processing.
• Increases query performance because storage access is faster and execution plans are better optimized.
• Results in the selection of more effective aggregates by the aggregation design algorithms, provided that user-defined hierarchies have been defined along the relationship paths.
Attribute relationships are sometime inherent and sometimes it is user defined, this would happen while defining ragged hierarchies.