Definition

SOA (So-Ah) stands for service-oriented architecture. It is  a design approach and philosophy – “architecture” -- for systems and  applications. SOA is generally seen as evolving out of distributed computing  and modular programming methods, such as object-oriented programming.

Business applications

There are a number of reasons why companies might move to a  service-oriented architecture. The most common reasons are to:

Reuse or share business processes as services. To simplify, services are collections of code that do something. This business processes - such as run a credit card payment or billing a client – can be “packaged”  as a service. Those services then can share or reuse that service either  internally or with external partners, generally over the Internet.

Respond more quickly to changing business needs. Since business processes can be packaged as services, IT can mix and match  services as needed to deploy new applications or update existing applications  quickly.

Simplify and reduce integration work. Most  integration work relies on point-to-point integration. This is an inflexible  approach that can cause integration to fail if a new system, application or  component is added or if any changes are made. Since SOA uses loose coupling,  it is said to simplify the integration work and reduce the chance that a  connection will fail.

Integrate legacy systems. Again, since SOA calls for  packaging application functions as services, you can service-enable legacy  systems, making it easier to access the data or functions on those systems.

For an example of how an online company, VetSourced, used SOA to further business goals, see “VetSource’s SOA Success  Story.”

Controversy

For an architecture, SOA has had its fair share of  controversy. Some question whether SOA is actually anything new or just a  glorified version of modular programming.

There is also the unresolved question of how many SOAs are successful. Burton Group analyst Anne Thomas Manes (see “Looking for SOA Success Stories”) noted she had a difficult time finding true SOA  success stories in early 2008 and, more recently, Gartner reported its research found interest and investment in SOA were declining. There are also  unresolved questions about how to calculate SOA's return on investment. (see “Execs Have a ROI Issue with  SOA” and “Incremental Approach Can  Help Ease SOA Pain”) That might be making organizations unsure of SOA's value.

Defining whether or SOA is successful is further complicated by the debate over what qualifies as an SOA and what does not. Despite  disagreements over the nuances of defining SOA, there are some widely agreed upon characteristics that make SOA unique.

For instance, Gartner defines the SOA style as having five qualities: modular (these modular pieces are referred to as services), distributable, describable, sharable and loosely coupled. These last two items  – sharable, sometimes called reusable, and loosely coupled - are generally  cited as the key difference between SOA and other styles of system design.

Another SOA-related controversy is that vendors have labeled products as SOA, causing some in the industry to fear companies will be misled and believe they are “buying” SOA.

Technical details

SOA itself is not tied to a particular language, middleware, interface or other technology component. That said, there are many supporting  technologies that can help with SOA deployments, including SOA governance tools, registry/repositories and enterprise service buses.

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