The scenario described in this chapter focuses on using integration using APIs and interfaces as a tool for providing application integration in the enterprise. It is interesting to contrast the application integration approach described in this chapter with the data integration scenario discussed in the previous chapter. The data integration scenario required very little programming, consisting mostly of configuring software. In contrast, the application integration approach depends mostly on programming to deliver a solution.
Although the scenario described in this chapter focused on integration with SAP, the general model can be applied to other large packaged application suites. The presentation layer is provided by employees using Web browsers. The Web middleware layer is implemented using IIS, ASP, and custom COM components. The application connector is implemented as a Windows NT Service using COM objects created with the Object Builder from the SAP DCOM Connector. These separate building blocks are loosely coupled using MSMQ messaging and distributed transactions.
This arrangement with a separate building block for integration with each end-point is typical in many application integration scenarios. The separate building blocks can be tailored to the scenario and provide the specific glue needed to communicate with a custom or packaged application. MSMQ can be used to provide loose coupling between the applications.