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Understanding Visual MainWin
Visual MainWin converts Microsoft Intermediate Language (MSIL) into Java bytecode then executes it on WebSphere. This conversion handles the difference between .NET and Java semantics while producing efficient and fully compliant Java bytecode. The key elements of the conversion are:

• Direct Mapping: The compiler directly maps object structure, classes, interfaces, and types as well as the flow of control semantics from .NET to the equivalent Java semantics.
• .NET Semantics: The compiler handles .NET semantics not present in Java such as .NET unsigned types and .NET value types. .NET delegates by generating Java bytecode with the equivalent functionality.

The .NET runtime environment is hosted on J2EE by an implementation of the .NET Framework in J2EE, provided by Mainsoft and based on the Mono project.

Figure 2 shows how this works through the Visual MainWin for J2EE technology stack. .NET-based code runs on the .NET Framework class library, implemented by using the Mono source code, compiled into Java bytecode, and hosted on WebSphere as well as the core Data and .NET classes from mscorlib (a fundamental part of the .NET Framework) implemented directly by Mainsoft on Java. These then run using standard Java packages such as JDBC. For example, .NET code built using the System.Data namespace will convert into Java bytecode using the Java-based implementation of System.Data that runs on top of JDBC.

Interoperability is achieved through native support. Since the runtime for all compiled code is WebSphere, the .NET programmer and applications can access Java classes, EJBs, and namespaces transparently from the .NET environment as though those classes were .NET classes. The JDK and J2EE classes are all available to the .NET developer should the need arise. It works both ways - .NET classes built on the unified platform are also available to the Java programmer and applications.

In a distributed environment, .NET code can reference Java code that's deployed as an EJB or Web Service. Since the entire environment is Java, point-to-point integration with EJB assets is available over RMI. The developer experience is simple - they create a proxy to the EJB in a way similar to that used for consuming Web Services. Additionally the .NET programmer can access the J2EE server context, which is useful, and necessary for manipulating JNDI objects such as data sources.

Conclusion
Managing mixed-mode systems is an intricate affair, made even more difficult by the additional layers of complexity that are added for interoperability. In this article we reviewed the various methodologies that are available to allow for interoperability and their impact on the complexity of the system. We explored the various solutions in the context of their impact on fault management, configuration management, accounting management, security, and interoperability. In addition, Platform Unification was shown to have a great impact on reducing the complexity of mixed-mode systems and positively affecting the management of the system.

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