Emergence of mixed-mode systems

Strategies for Interoperability
There are several strategies that allow for interoperability between.NET- and WebSphere-based software platforms. These include Web Services, bridging solutions, cross-platform implementations of .NET, and an innovative Platform Unification approach from Mainsoft where ASP.NET code runs on WebSphere, using the J2EE runtime, and allowing for much lower-level interoperability than achieved with other solutions.

Web Services
Web Services are abstract entities that encapsulate business logic using XML for discovery, description, and communication. In the example of a J2EE backend and a .NET frontend, a Web Service layer can be introduced that wraps the business logic of the WebSphere backend and makes it accessible to the .NET frontend. This form of architecture is called loosely coupled. A major selling point and strength of the WebSphere Application Development environment is just this – easing the service orientation of the business assets that are deployed on WebSphere

Performance Management: Here is where Web Services break down from a management point of view.
Bridging solutions are tightly coupled solutions providing a messaging transport and translation layer between components running on diverse systems.

Fault Management: Web Services are widely adopted and are associated with many standards so that if the web Service is implemented using a standard, then it can be trusted to meet the appropriate criteria. In the case of management and fault management, WS-Management and MOWS standards encapsulate this. Configuration Management: Standards such as WSDM and MOWS address the issues of configuration management such as service changes, deployment, and lifecycle management.
Accounting Management: MOWS address the functionality of metering services as well as auditing and integration with modules such as Service Level Agreement (SLA) management.
Management may also want to implement company-wide department-level applications that require interoperability or migration to a J2EE architectureDesire for Service Orientation: Many companies want to simplify their interoperability to become service-oriented either within the enterprise and/or to external customers. Integration directly with business partners or customers often necessitates a cross-technology interoperability solution. High Development Costs: The business driver of cutting costs may also impact development costs.

A word of caution is on overheads about Web services. Web Services incur a large performance overhead, so while it may be tempting to wrap high-performance EJBs running on a z Series platform in Web Services to expose them to other applications also, so as not to lose the benefits of the technology and the platform to compensate overhead that is incurred.