Service Oriented Architecture (SOA) is an architectural style that helps enterprises in integrating business processes so as to make information accessible over a network. SOA is not just an architecture of services seen from a technology perspective, but the policies, practices, and frameworks by which we ensure the right services are provided and consumed.
For e.g: Health organizations have several Disparate systems (or Data Processing Systems) and components that are not connected to each other or they are not even synchronized. such as Patient data at the hospitals or at PCP office cannot be accessed by Doctors in the Ambulatory care system, the nurse station cannot efficiently obtain comprehensive patient data from Doctor’s office or Clinic. All most all departments work independently, that do not intend to work with other departments :). This leads to problems with payment systems, health insurance lams stored in legacy claim systems that can cannot be accessed or shared easily.
Disparate system: Is Data Processing System without exchanging data or interacting with other computer data processing systems
System integrators can build applications by composing one or more services