COM+ is the next stage in the evolution of Microsoft's component middleware. It integrates and extends the features of COM and MTS to make it easier to develop, deploy, and administer component-based applications.
COM+ makes development easier by unifying the COM and MTS programming models. It emphasizes a declarative model for accessing services, reducing the number of APIs developers must understand. Deployment and administration are simplified by uniting the COM and MTS administrative model and tools. In COM+, the distinction between COM and MTS disappears.
COM+ also simplifies development by providing a default implementation of the infrastructure services most distributed applications need, so developers do not have to implement and maintain infrastructure code themselves. Developers focus on writing their business logic and let COM+ handle the infrastructure. COM+ services are accessed by setting a few attributes on components, classes, or interfaces. COM+ improves on all the services found in MTS 2.0 and adds queued components, the Event service, IMDB, and dynamic load balancing via application clusters.
Customer investments in COM and MTS will be fully preserved by COM+. All existing COM and MTS components and applications should continue to work without modification, with no loss in performance. In most cases, modifying components or applications to use COM+ features is simply a matter of deploying components using the COM+ administrative services and setting attributes. The techniques for developing distributed, component-based applications discussed in this book will continue to work for COM+, with some minor changes in terminology and tools.