Meta Object Facility

Although Microsoft's support of UML has helped the standard to proliferate, there are significant UML advocates that offer competing repository technology. Unisys Corp. is one of several such companies. Unisys, Mission Viejo, Calif., has invested heavily in object repository technology. The Universal Repository (UREP), first released in 1995, is now in its third major release and supports UML V1.1 and the Meta Object Facility (MOF) interchange format.

According to Sridhar Iyengar, Unisys fellow, "It is a collaborative effort. Integration of MOF and UML is very involved. The MOF describes various information models, and uses UML notation for describing information models. The repository implementation itself and the APIs are based on MOF."

UREP is independent of middleware technology and supports Corba, COM and Java middleware. Microsoft Repository, on the other hand, is based on COM and is available today only on Microsoft platforms. A partnership with Platinum Technology to port Microsoft Repository to additional platforms is expected to bring the Repository to the enterprise.

Iyengar anticipates that UREP will be implemented more in the enterprise environment, and that Microsoft Repository will fit more into the Microsoft Windows desktop environment. "We focus more on the heterogeneous environment, where the world is more than NT," he said.

UREP is also licensed and used in third-party tools. According to Iyengar, Select Software Tools Inc., Irvine, Calif., has chosen to implement UREP in its object analysis and design tools. BEA Systems Inc., Sunnyvale, Calif., has also licensed UREP and has integrated it into BEA enterprise products.