Using XML Encoding

Extensible Markup Language (XML) interchange is supported by MSMDCXML.dll, which is installed with Microsoft® SQL Server™ 2000 Meta Data Services.

Meta Data Services supports exporting and importing of meta data through the Meta Data Coalition (MDC) Open Information Model (OIM) XML Encoding format. XML Encoding defines rules for generating XML elements that map to information model elements. The XML Encoding format is published by the MDC and implemented in Meta Data Services to support the exchange of meta data. In Meta Data Services, exporting and importing using XML enables you to exchange meta data with other repositories or tools.

Export and import using XML is supported through a dual interface. You can use the objects separately or together to perform a seamless exchange:

• The export process generates an XML document that contains XML-tagged meta data. The XML document can be expressed in memory or stored in a file.
  
  
• The import process converts XML documents to object instance data in a repository database. You can import an XML document from memory or from a file.

The exchange of meta data is directed by your application code. By instantiating export and import objects and calling the methods supported by the objects, you can complete the entire exchange programmatically.

Backward Compatibility

Meta Data Services still recognizes models that are based on earlier versions of the OIM. If you have been using XML Interchange Format (XIF) to import and export repository data, you can still do so. You can also use MDC XML Encoding to achieve the same objective. However, you cannot combine XIF and MDC XML Encoded formats. You must use either XIF or MDC XML Encoding to perform an import and export. You cannot use both in the same exchange.

Although MDC XML Encoding supports an XML format that most closely corresponds to the most recent version of the OIM, the import and export features of MDC XML Encoding can map previous versions of OIM-based models to the newest version of OIM. This mapping occurs automatically during an import or export operation, and it does this without modifying your information model. The advantage of this mapping is that you can exchange data between information models that are based on different versions of the OIM.

The only exception to this mapping correspondence occurs for new Unified Modeling Language (UML) and OIM elements that are not defined by older versions of the OIM. If your objective is to transfer repository data from information models that use new definitions to information models that use older definitions, you will experience some data loss in the conversion. Specifically, the portion of data from the new model that cannot be accommodated by the older model is logged to an error file.

For more information about XML interchange formats and information models, see Upgrading an Information Model.

Additional Topics

The following topics provide more detailed information about XML encoding.

See Also

Meta Data Coalition

OIM in Meta Data Services