Fundamentally, SOA is a development methodology that encourages sharing of remotely invocable application functions throughout networks. It's a way of doing more with less, where applications can be built more quickly and incrementally, with fewer lines of original code.

The upside of SOA is that the marginal cost of building new applications will continue to drop as the service-reuse rate climbs. The catch is that there's a significant ramp-up cost, because adopting an SOA means you're going to need to rethink many of your traditional approaches to application modeling, development, integration, deployment and management.

"I can guarantee there's a cheaper way to build your next product, but there's no cheaper way to build your next 20 products," says Christopher Crowhurst, vice president and principal architect at Thomson Learning.

Forrester Research analysts Ken Vollmer and Mike Gilpin report that SOA-based development can be twice as much as traditional approaches when viewed solely with respect of building a particular application component.

But when that application component is reused over and over, SOA becomes more than 30% more cost effective than traditional development approaches.

Cost savings

Many of the savings from SOA stem from its ability to consolidate silos of redundant application functionality and data throughout organizations.

Fewer software licenses and servers translate into cost savings in capital and operating budgets. Fewer redundant software components translate into less need for redundant programming groups. Application consolidation onto fewer platforms reduces software life-cycle costs, which Gartner says can be six times greater than license costs.

However, SOA requires a significant upfront investment. Standard Life Group, an Edinburgh, Scotland, insurance company, maintains three SOA-implementing development groups with about 500 people, about half of whom are delivering SOA services and applications. A staff of seven manages their SOA-enabling distributed-application infrastructure.

On the plus side, "we've saved over £2.8 million in development costs over the past three years based on reuse of existing functionality within the service catalog," says Derek Ireland, group tech solutions manager.