SOA is a confusing term because it describes two very different things. The first two words describe a software development methodology. The third word, architecture, is a picture of all the software assets of a company, much as an architectural drawing is a representation of all the pieces that together form a building. Therefore, service-oriented architecture is a strategy that proclaims the intention to build all the software assets in the company using the service-oriented programming methodology.
What is a service?
Services are software chunks, or components, constructed so that they can be easily linked with other software components. The idea behind these services is simple: Technology should be expressed in chunks that business people can understand rather than as an arcane application such as ERP or CRM.
