17.2 Background: Components of the OMG Metamodeling Architecture

   The CWM specification addresses the metadata interchange requirement of the OMG repository architecture specific to the data warehousing domain. The CWM specification leverages the following standards:

• MOF, the Meta Object Facility, is an OMG metadata interface standard that can be used to define and manipulate a set of interoperable metamodels and their instances (models). The MOF also defines a simple meta-metamodel (based on the OMG UML - Unified Modeling Language) with sufficient semantics to describe metamodels in various domains starting with the domain of object analysis and design. CWM uses MOF as its meta-metamodel.

• UML, the Unified Modeling Language, is an OMG standard modeling language for specification, construction, visualization, and documentation of the artifacts of a software system. CWM uses UML as its graphical notation, and defines a base metamodel; that is, the CWM Object Model that is consistent with the core UML metamodel.

• XMI, or XML Metadata Interchange, is an OMG standard mechanism for the stream-based interchange of MOF-compliant metamodels. XMI is essentially a mapping of the W3C’s eXtensible Markup Language (XML) to the MOF. By being implicitly MOF-compliant, any CWM model instance can be interchanged by enabled tools using the facilities of XMI.

   In summary, CWM is a domain-specific extension of the OMG’s Metamodeling Architecture, and as such, implicitly supports the MOF, UML, and XMI standards. Although CWM has certain “compatibilities? with various other standards (as outlined in subsequent sections), these compatibilities should be regarded as touch points for mapping or integration; they do not represent dependencies of any kind. CWM is not dependent upon any standards outside of those of the OMG Metamodeling Architecture.