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Discussion of MOF, OMG and XML and XMI

The XMI (proposed) spec is on the OMG server ad/98-07-01 (base spec, DTD production rules, design guidelines) and ad/98-07-03 (DTDs for UML and MOF for exchanging models and metamodels respectively) . A preliminary spec' was presented in June.

The key points to note are as follows :

1. MOF is OMG's adopted technology for defining metamodels (these are analogous to DTDs) and is based on the well established 4 layer metamodelling architecture
2. MOF is the repository API (uses CORBA IDL) for managing OMG's metadata for all MOF compliant metamodels in distributed environment
3. UML was the first metamodel that was adopted by OMG
4. Additional metamodels are being defined (eg: data warehouse management, business objects, component models, workflow...)
5. XML is being proposed as part of the Unisys/IBM et al XMI submission to the Stream based Model Interchange Format RFP. There are other proposals.

Some of these standards may be applicable to the XML repository efforts as identified below. (eg: UML/XML work is specifically identified below)

This co-operation across standards group is a good sign.

Sridhar Iyengar

Unisys Fellow

sridhar.iyengar@mv.unisys.com

Unisys Corporation

Editors Note:

If you download the OMG MOF document it is hard to unravel. The specific sections you should focus on are "1.1 Four Layer Metamodel Architecture", then "1.2 Organization of the MOF", and then "1.3 How the MOF Model is Described". 1.3 especially details in subheadings each of the properties of the MOF Model. These look to potentially have close equivalents in the XML Glossary for XML/EDI.

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