124 DB2 Cube Views: A Primer
3.6 Summary
In this chapter, we looked at the basic concepts and terminologies involved when
describing a cube model in DB2 Cube Views. Cube modeling with DB2 Cube
Views is designed for star (or snowflake) schemas. The objects that describe a
cube model are the fact, dimensions, hierarchies, joins, attributes and
attribute-relationships.
This chapter also demonstrates the different methods of building a cube model in
DB2 Cube Views. A cube model can be built by import, with Quick Start wizard or
from scratch. When building a cube model by import, you start with OLAP
metadata that is already available, which has been passed through a suitable
bridge to transform it into DB2 Cube Views format. When building a cube model
from scratch, you can either use the Quick Start wizard or build the metadata
objects yourself. Using the Quick Start wizard builds a cube model using existing
joins between fact and dimension tables and this requires RI (referential integrity)
implemented for the star schema.
You can also choose to build a cube model by sequentially defining the objects
(facts, dimensions, joins) yourself.
Note: Even if Referential Integrity is highly recommended for DB2 Cube Views
and pre-requisite for Quick Start wizard, it is not mandatory when building the
cube model manually and informational constraints may be used (see4.4.2,
“Define referential integrity or informational constraints” on page 136).
Important: It is RI alone (along with the variation introduced in DB2 V8.1
called Informational Constraints) that informs the DB2 optimizer of the
relationships that guide query rewrite and MQT routing.

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