Service Oriented Architecture
Service Oriented Architecture (SOA) is an evolution of the fundamentals governing a component based development. Component based development gives an opportunity for greater code redefine than what is possible with Object Oriented (OO) development.
SOA gives even greater code reuse by utilizing component based development, OO development and also by organizing and identifying well-defined and non-repeatable program services into a hierarchy of composite services. You can create a new application from a existing service. E.g: you can create use of Google's search service and eBay's services with the service you intend to give.