Enterprise SOA

The ESA stack, layer by layer

With the general relationship of service consumers and providers in mind, we can now turn to the idea of how the ESA stack works inside both consumers and providers. Each layer of the ESA stack has been conceived and designed to play a supporting role to create service consumers (usually composite applications) and service providers. Each layer has a specific role to play that promotes flexibility, reuse, and ease of development in concert with the other layers. Before we examine each layer in detail, we will take a look at the challenges each layer must overcome to do its job.

What challenges face the ESA stack?

As Figure 5-3 shows, the ESA stack consists of five layers, each designed to address an enduring challenge that has faced enterprise application architects since the beginning of the industry. The vision of ESA has made those challenges more acute in several ways.

First, one of the promises of ESA is that standard software delivered as a set of services can both better fit the requirements of a business and be recombined to solve many more problems. SAP will recombine services to provide automation of many more processes flavored for industry verticals. This expansion of automation will mean that more UIs will need to be created to assist people who will be playing various roles in these automated processes. More processes automated and more UIs mean that development tools must become more productive and applications must become easier to maintain. ...