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Chapter 3 • Enterprise Systems Architecture 75

any service consumer and service provider. It could also involve two or more services coordinating
some activity, as long as they follow SOA standards.
The SOA standard includes a description language for all functions or services that have
active programming services that are called on to perform business processes. Each interaction
is independent of each and every other interaction and the interconnect protocols of the
communicating devices with different infrastructure components. Because services are
independent of the operating system platform, a consumer from a device using any operating
system in any language can use this service. SOA is similar to Web services, but it is not the
same. Web services is an application of SOA with such Web-based technologies as SOAP and
XML. SOA is more than a set of technologies; it is a standard that runs independent of any
specific technologies.
SOA is a software development model based on a contract between a consumer (client)
and a provider (server) that specifies the following:
•Functional description of the service
•Input requirements and output specifications
• Precondition environment state before service can be invoked
•Postcondition environment state after service has been executed
•Error handling when there is a breakdown

Figure 3-6 illustrates basic components of service-oriented architecture. It shows a
consumer sending a service request message to a provider. The service provider returns a reply
message to the consumer. The request and subsequent replies are defined in a service-level
agreement that is understandable to both the service consumer and service provider.
In short, SOA consists of several best practices that permit an organization to conceal the
complex nature of technology while supplying agile resources for the business. It rearranges
the capabilities of different business applications and turns them into business services. These
services are then converted into business processes. It can then be said that SOA permits the
business flexibility and agility.
Agility and flexibility allow an organization to do many things that will better serve their
business. These things include, but are not limited to, the following: improving business visibility,
reducing the cost of integration, increasing the business’ agility, and increasing the reuse of
services. Depending on the type of problems the organization is trying to solve with SOA, these
benefits and others not listed can provide a monumental return at several different levels. In enter-
prise content management, SOA can connect dissimilar systems and integrate enterprise content
management into areas where it did not have a presence.

BENEFITS AND DRAWBACKS The main characteristic of an SOA is that of a loosely coupled,
document-oriented interaction model. The key benefits of SOA, therefore, are scalability,

request
Service
reply
Consumer Provider
FIGURE 3-6 An SOA Architecture