The wedding between the two key object software models has at last taken place, after a long engagement, writes Graham Lea.

Microsoft has announced plans to open up Component Object Model(Com) enabling it to link with third party systems such as the Object Management Group?s (OMG?s) rival Corba model.

It has a particular eye on the back-end transaction systems that will be key to Microsoft?s ambitions to dominate high-end computing. This will involve much closer links between Com and Corba.

The move has been a long time coming. Negotiations started way back in 1994, when Microsoft approached the OMG along with Digital and Candle with a proposal for platform interoperability. Under this plan Corba would comply with Microsoft?s Object Linking and Embedding (OLE) standards ? of which Com forms part. This was not acceptable to the OMG, an industry standards group which wanted Com and OLE instead to submit themselves to the authority of Corba.

Microsoft went on to invent Dcom, a distributed version of Com, claiming at its analysts? meeting in July 1997 that ?Dcom is not a Windows-only spec?.

At that time, Microsoft was also saying that, as far as Corba and Com were concerned, ?there?s going to have to be some level of interoperability between them?. More recently, Microsoft decreed that Dcom should be called Com again.

Microsoft previously regarded Com as a direct competitor to Corba, but potential customers among large businesses made it clear to Microsoft that major systems developments require a heterogeneous environment rather than a Windows-only strategy; frameworks rather than interoperability at the binary level; multiple inheritance; and persistent rather than transient objects. All this meant that Com and Corba had to make their peace.

Although Microsoft had accepted that it would have to work with Unix and mainframe applications, and that Corba was the key to this, its concern had been to find a way of controlling mainframe standards. It saw Com as a way to do this.

An early move in this direction was when Microsoft arranged for Hewlett-Packard, Digital and Software AG to port Com to Unix platforms.

In the so-called enterprise market, an important strategic objective for Microsoft is to control the server ? especially in transaction based systems. This requires more dexterity in the two-way transfer of data than Microsoft technology has previously exhibited. It also demands a fully heterogeneous environment with two-way interoperability between Corba and Com.

Microsoft?s approach to the enterprise market is to partner with those industry leaders that are already commonly accepted as reliable suppliers.

Microsoft?s plan is to become more like an integrator than a full-line developer of technology, leaving the technical details of the integration in the non-Windows world to partners. The squeeze was on for Microsoft?s Transaction Server (MTS) to interoperate with the non-Microsoft world.

The OMG has developed interworking specifications for OLE2, Com, Dcom, ActiveX, and Com+ over the past three years. Microsoft finally decided that Com and Corba must coexist earlier this year.

OMG chief executive Richard Soley said: ?We are delighted at Microsoft?s recognition that Corba is now the standard for distributed application integration in the enterprise.?

As a reluctant member of the OMG, Microsoft initially preferred to avoid working with Corba specifications, instead keeping tight proprietary control by licensing Com to a number of vendors, including Digital, HP, Iona, Siemens Nixdorf, and Silicon Graphics.

In a series of recent announcements, Iona, Visual Edge, and Digital have expanded on how they are working with Microsoft to provide the ?middleware? to link the Windows and non-Windows worlds for large users.

Iona, the Dublin-based developer of object middleware, has had its Orbix Object Transaction Monitor endorsed by Microsoft. It will be integrated in MTS, but Microsoft has said that its arrangement with Iona is non-exclusive.

Annrai O?Toole, Iona?s chief technology officer, said: ?We have a new friend in Microsoft? and went on to say that MTS had ?improved dramatically? since its launch. Iona said it is shipping the only Corba-conformant transaction server that can operate with Microsoft?s Com+.

Iona licensed Microsoft?s technology in January for its Orbix Comet, a bridge that links Com objects into a Corba environment. Paul Hickey, Iona?s vice president of product alliances, confirmed that the company had found it easier to work with Microsoft than to convert Com to the OMG?s Inter-Orb Protocol IIOP. For this reason it agreed to license Microsoft?s sourcecode.

Hickey did not say if Iona had paid for access to the Com code, or whether Microsoft was so keen to push its way into the enterprise world that it was willing to pay Iona to help with this.

A spokeswoman for the Frish company said that its customers were less concerned about the religious wars than in getting interoperability, and that most of its customers were closer to Com than Corba.

Nevertheless, ?Iona is still 100% behind the OMG,? she said.

Visual Edge Software is an enterprise applications integrator and developer of the Object Bridge product for Com-Corba inter-operability.

Visual Edge?s approach with Object Bridge is to map between Com and Corba at the object level. The advantage of this approach is that it is faster and does not need sourcecode licensing, the company says.

Visual Edge characterises Iona?s middleware approach as being like Esperanto, acting as a common language, whereas its Object Bridge technology is more like simultaneous translation. Object Bridge allows bidirectional interoperability between Corba, Com, Dcom, Java, SNMP and SAP R/3 applications, it says.

In similar vein, Microsoft also said that Digital had announced plans to provide interoperability between MTS and Digital?s ACMS, Digital?s transaction management software for OpenVMS that had its origins in the mid-1980s