The Metadata Challenge
On the one hand, metadata—or data that describes data—is incredibly important. Virtually all types of interactions with a database require the use of metadata, from knowing the datatypes of the data to understanding the business meaning and history of data fields.
On the other hand, metadata is useful only if the tools and clients who wish to use it can leverage it. One of the great challenges is to create a set of common metadata definitions that allows tools and databases from different vendors to interact.
There have been a number of attempts to reach an agreement on common metadata definitions. In 2000, a standard was ratified that defines a common interface for interchange of metadata implementations. Named the Common Warehouse Metadata Interchange (CWMI) by the Object Management Group (OMG), this standard is based on XML interchange. Oracle, one of the early proponents and developers of the technology in this standard, has already released CWMI bridges for exchanging metadata in its own products. Examples include Oracle bridges provided to exchange metadata from the Oracle Warehouse Builder repository to Oracle Discoverer and Oracle Express. OWB3i also includes a metadata viewer for viewing data lineage and impact analysis within the repository; the viewer is planned to be extended through CWMI to view other repositories in the future.
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