On the one hand, metadataor descriptive data about datais incredibly important. Virtually all types of interactions with a database require the use of metadata, from datatypes of the data to 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 was one of the early proponents and developers of the technology in this standard. Oracle has a CWM bridge for exchanging metadata stored in the Oracle Warehouse Builder repository. OWB also includes a metadata viewer for more detailed metadata reports, and a viewer for data lineage and impact analysis diagrams.