Section 6.2. Fundamental SOA

6.2. Fundamental SOA

A fundamental SOA consists of two layers: the basic layer and the enterprise layer. Distinguishing these two layers helps single applications to define a proper high-level structure. It also enables two or more applications to share business-logic and live data. Although a fundamental SOA represents a rather simple approach, it provides a strong platform for large enterprise application landscapes. In fact, it is a major improvement compared to many of today's real-world scenarios. It is also an excellent starting point for the introduction of an enterprise-wide SOA because it enables enterprise organizations to start small on the technical side and focus on other critical success factors (see Chapter 12, "The Organizational SOA Roadmap").

A simple example (see Figure 6-4) shows how one application can be divided into meaningful components using an SOA. The Airline Web site utilizes four services that encapsulate the major business entities and their behaviors that are relevant to the business processes that are exposed to the customers.

Figure 6-4. A fundamental SOA consists of two layers. Application frontends and basic services provide a fully functional base for enterprise applications.

We can now expand the original example by adding another application. A key characteristic of a fundamental SOA is that it enables two or more applications to share live data and business logic. In our example, we consider a traditional billing application that is required to keep track of terms of payment and the handling of demand notes (see Figure 6-5). This type of application is traditionally provided with customer and billing data through nightly batch jobs. Integrating billing and invoicing into a fundamental SOA enables the booking and the billing applications to share live data. In practice,^[1] this means that the billing application gets access to the customer service and billing services that, in turn, make batch processes that transfer data between the applications obsolete.^[2] In addition, there are clear benefits for the booking system. As a result of up-to-date billing, the booking system also has access to precise, up-to-date data at any time. This increases the capability of the booking system to treat customer requests in a more appropriate manner. For example, a change in the credibility status of a customer, which is detected by the billing system, is instantly available for the booking system. As previously mentioned, in many traditional environments, this information is only available to the databases of the booking application after nightly batch updates.

^[1] It should be noted that a real-world scenario would be much more complex, as depicted in Figure 6-5. It would involve a customer care application, a sort of workbasket, and additional business services. However, the aforementioned benefits still apply.

^[2] Note that an update in one application is instantly visible in the other application. In a traditional EAI scenario, you should consider decoupling the original data change from notifying the second application due to throughput and performance considerations. In the SOA world, these notifications are obsolete.

Figure 6-5. Enterprise application integration becomes obsolete if several applications share live data.

The introduction of a fundamental SOA is the first important step toward a truly SOA-enabled enterprise. The following summarizes the main characteristics and scope of a fundamental SOA:

• A fundamental SOA is an appropriate base for an enterprise application landscape.

• Due to its simplicity, it is technically easy to implement.

• It is a good starting point for an SOA that enables the introduction of more advanced expansion stages in the future.

• The application frontends are still complex. They must cope with the control of business processes and the full integration of the backend.

• A fundamental SOA increases the maintainability of an enterprise application landscape.

• Shared services can make data replication (enterprise application integration) largely obsolete.