Common Warehouse Metamodel (CWM)

The Common Warehouse metamodel (CWM) specifies interfaces that can be used to enable easy interchange of warehouse and business intelligence metadata between warehouse tools, warehouse platforms and warehouse metadata repositories in distributed heterogeneous environments. CWM is based on three standards:

  • UML - Unified Modeling Language, an OMG modeling standard
  • MOF - Meta Object Facility, an OMG metamodeling and metadata repository standard
  • XMI - XML Metadata Interchange, an OMG metadata interchange standard

The UML standard defines an object-oriented modeling language that is supported by a range of graphical design tools. The MOF standard defines an extensible framework for defining models for metadata, and providing tools with programmatic interfaces to store and access metadata in a repository. The XMI standard allows metadata to be interchanged as streams or files with a standard format based on XML. The complete architecture offers a wide range of implementation choices to developers of tools, repositories and object frameworks. XMI in particular lowers the barrier to entry for the use of OMG metadata standards.

These three standards form the core of the OMG metadata repository architecture as illustrated in the following figure.

OMG metadata repository architecture

Key aspects of the architecture include:

  • A four layered metamodeling architecture for general purpose manipulation of metadata in distributed object repositories. See the and specifications for more details
  • The use of UML notation for representing metamodels and models
  • The use of standard information models (UML) to describe the semantics of object analysis and design models
  • The use of MOF to define and manipulate metamodels programmatically using fine grained CORBA interfaces. This approach leverages the strength of CORBA distributed object infrastructure.
  • The use of XMI for stream based interchange of metadata

This specification mainly consists of definitions of metamodels in the following domains: 

  • Object model (a subset of UML)
  • CWM foundation 
  • Relational data resources
  • Record data resources
  • Multidimensional data resources
  • XML data resources
  • Data transformations
  • OLAP (On-line Analytical Processing)
  • Data mining
  • Information visualization
  • Business nomenclature
  • Warehouse process
  • Warehouse operation


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