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The CWM Multidimensional metamodel is a generic representation of a multidimensional database.
Multidimensional databases are OLAP databases that are directly implemented by multidimensional database systems. In a multidimensional
database, key OLAP constructs (dimensions, hierarchies, etc.) are represented by the internal data structures of a multidimensional
database server, and common OLAP operations (consolidation, drill-down, etc.) are performed by the server acting on those
data structures. Multidimensional databases are often classified as “physical OLAP? or “MOLAP? (memory-based OLAP) databases.
Multidimensional databases offer enhanced performance and flexibility over OLAP systems that simulate multidimensional functionality
using other technologies (for example, relational database or spreadsheet):
• Performance: Multidimensional databases provide rapid consolidation times and formula calculations, and consistent query response times regardless of query complexity. This is accomplished, in part, through the use of efficient cell storage techniques and highly-optimized index paths.
• Flexibility: The specification and use of multidimensional schemas and queries (including the design of cubes, dimensions, hierarchies, member formulas, the manipulation of query result sets, etc.) can be accomplished in a relatively straightforward manner, since the server directly supports (and exposes) the multidimensional paradigm.
The CWM Multidimensional metamodel does not attempt to provide a complete representation of all aspects of commercially available,
multidimensional databases. Unlike relational database management systems, multidimensional databases tend to be proprietary
in structure, and there are no published, widely agreed upon, standard representations of the logical schema of a multidimensional
database. Therefore, the CWM Multidimensional Database metamodel is oriented toward complete generality of specification.
Tool-specific extensions to the metamodel are relatively easy to formulate, and several examples are provided in Volume 2,
Extensions, of the CWM Specification.