With regard to the functional specifications, the business departments are able to express their needs – summarily – in the form of lists of information that they expect from the system. By doing this, they describe the features that ultimately need to be supported by a system.

As for IT teams, their task is to group as a service the messages delivering the requested information.
In an SOA context, a service is a consistent and indivisible processing unit that coordinates a set of messages and events, the objective being to execute one or several processing operations.

The services may be matched up to the operations executed at each step of enterprise business processes. Services can thus be seen as the pivotal point between the business functions and the information technology. The business functions perceive the services by way of the functionality provided, and the IT engineers perceive them as elements of the system architecture.