Chapter Four. Service-Oriented Application Integration

This chapter describes the next dimension in application integration: the joining of applications together through the exchange of simple information and the linking of application services.

This approach is nothing new; we have been doing this for years through custom coding, or through standards such as distributed objects. However, with the advent of Web services we now have another tool in the shed that will get us to SOAI...hopefully, with more success.

You should focus on the concepts more than the mechanisms while reading this chapter. We'll talk more about the mechanisms later in the book. Also, keep in mind that this approach to application integration is more invasive, thus more costly. Therefore, you have to justify its use.

By now we know that application integration is innate to almost all e-Business system development. Applications can no longer exist as standalone entities. Instead they must share information with other information systems, inside and outside corporations. Indeed, organizations have been moving closer to a well-integrated enterprise and (in some instances) supply chain that provides most information systems with access to real-time information from other applications when needed. This Information-Oriented Application Integration (IOAI) is the most popular way of doing application integration today.

However, as real-time information exchange (IOAI) between systems improves, the trend is to view application integration at a higher level of abstraction, or through business processes. This approach allows those exchanging information between various applications to view the information flow in the context of a business model, or business processes that define business logic, sequence, subprocesses, and hierarchies of processes. This ability to control application integration through abstract business process automation abstractions that also account for lower-level mechanisms such as transformation and intelligent routing can be called BPIOAI (see Chapter 3).

While IOAI and BPIOAI provide a functional solution for many application integration problem domains, it is the integration of both application services that generally provides more value in the long run, albeit at a cost.

Organizations have been looking for mechanisms to bind applications together at the service level for years. Some successful mechanisms include frameworks, transactions, and distributed objects, which are all in wide use today. However, the notion of Web services, such as Microsoft's .NET strategy, not to mention strategies from IBM, BEA, HP and Sun, is gaining steam. The goal is to identify a new mechanism that can better leverage the power of the Internet to provide access to remote application services through a well-defined interface and directory services. The proper use of Web services in the context of application integration is the future of application integration. Therefore, much of the remainder of this book will concentrate on this aspect of implementation, as well as review competing standards and technologies.