SOA (Service Oriented Architecture)

In short, SOA refers to an architecture that is built on deployed services, enabling reuse at runtime (opposed to objects and components that can, and must be be, reused at compile time).

IBM defines SOA as follows:

• A service is a functional unit of an application
• SOA inter-relates services through interfaces and contracts
• Interfaces are independant from hardware, operating system, and programming language ("loose coupling")
• While this is true for CORBA, too, IBM claims Web Services are more dynamic and flexible (good question "why?")
• The ESB (Enterprise Service Bus) provides workflow and transformations between business processes and technical processes
• SOA doesn't define the technical details of how services interact

IBM's introductionary text into SOA and Web Services generously mixes the terms mentioned above with Grid Computing, UML, MDA, BPEL, and adds some RUP for good measure. IMHO, if it wouldn't be for the sexiness of XML, Web Services, and the Internet, nobody would think that SOA is The Next Big Thing. I am convinced that in 2004 SOA (and IBM's term "on demand business") will become a buzzword as overutilized as "XML" and "Web Services".