Package org.omg.cwm.resource.multidimensional

The CWM Multidimensional metamodel is a generic representation of a multidimensional database.

See:
Description

Interface Summary

CompositesReferenceComponents	A Dimension may reference other instances of Dimension in order to derive more complex dimensional structures.
Dimension	Dimension represents physical dimension in a multidimensional database (e.g., a dimension object defined by the programming model/API of an OLAP database server).
DimensionedObject	DimensionedObject represents an attribute of Dimension.
DimensionOwnsMemberSets	A Dimension may own any number of MemberSets.
DimensionsReferenceDimensionedObjects	A Dimension may reference several instances of DimensionedObject.
MdschemaOwnsDimensionedObjects	A Multidimensional Schema may own any number of DimensionedObjects.
MdschemaOwnsDimensions	A Multidimensional Schema may own any number of Dimensions.
Member	Member represents a member of a Dimension.
MemberSet	MemberSet represents the collection of Members associated with an instance of Dimension.
MemberValue	MemberValue represents an instance value of a Member.
Schema	Schema contains all elements comprising a Multidimensional database.

Package org.omg.cwm.resource.multidimensional Description

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 (e.g., 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 straight-forward 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.

Organization of the Multidimensional Package

Dependencies

The Multidimensional package depends on the following packages:

• org.omg::CWM::ObjectModel::Core
• org.omg::CWM::ObjectModel::Instance

Major Classes and Associations

The major classes and associations of the Multidimensional metamodel are shown in Figure 11-1:

Schema is the container of all elements comprising a Multidimensional model. It also represents the logical unit of deployment of a Multidimensional database instance.

Dimension represents a physical dimension in a Multidimensional database. Whereas the OLAP metamodel defines "dimension" as a purely conceptual entity, this Dimension represents the dimension object exposed by the programming model of a Multidimensional database.

A Dimension may reference other instances of Dimension to form arbitrarily complex dimensional structures (e.g., hierarchies with varying levels of detail).

DimensionedObject represents an attribute of Dimension. Examples of DimensionedObjects include measures (variables), formulas, consolidation functions, member alias names, etc. DimensionedObjects are contained by the Schema and referenced by the Dimensions that use them.

MemberSet represents the collection of Members associated with an instance of Dimension, and MemberValue represents an instance value of a Member. MemberSet, Member and MemberValue enable the specification and interchange of both M1-level Multidimensional models and associated M0-level data values.

Inheritance from the ObjectModel

Figure 11-2 illustrates the inheritance of the Multidimensional classes from metaclasses of the Object Model.

For Additional Information

For additional information, see the CWM specification at http://www.cwmforum.org.

Since:

1.0