Short note: SOA and SOAP

SOA (Service-Oriented Architecture)

SOA is a design style in which software is built as a set of loosely coupled, reusable services. Each service performs one business function (for example "check balance"), has a published interface, and can be used by other applications over a network irrespective of platform or language.

        Service registry (UDDI)
         ^ publish      | find
         |              v
 Service provider <-- Service consumer
          bind and call (SOAP / HTTP)

Three roles: service provider (creates and publishes the service), service registry (directory where services are listed), service consumer/requester (finds and invokes it).

Benefits: reuse, interoperability, flexibility, easier integration of legacy systems, scalability.

SOAP (Simple Object Access Protocol)

SOAP is an XML-based protocol for exchanging messages between services, usually over HTTP. A SOAP message has an Envelope containing an optional Header and a mandatory Body (and a Fault element for errors).

<soap:Envelope xmlns:soap="http://www.w3.org/2003/05/soap-envelope">
  <soap:Body><GetStudent><Id>5</Id></GetStudent></soap:Body>
</soap:Envelope>

Relation

SOA is the architectural idea; SOAP is one standard way (with WSDL and UDDI) of implementing communication between the services in a SOA. Web services can also be provided in a SOA using REST.