It is important to budget for "the range of expenses that follow Web services into an enterprise," writes Thomas Erl in his recent book aptly titled Service Oriented Architecture. "Web services are expensive. That is, good Web services require a great deal of work to ensure that they truly are 'good.' Each service you develop can potentially become an important part of your IT infrastructure. Not only can services expose legacy apps and various types of business (and reusable) functionality, they can represent and even enable entire business processes."
Erl notes that how a service is designed "requires a solid knowledge of the business model within which it will operate, and the technologies upon which it will be built. Services that will form (or intend to participate in) a future SOA also need to be in alignment with the design strategy and accompanying standards that are part of the overall SOA implementation plan."
Erl points out to developers (and moneymen) that custom-develop services on top of existing legacy environments that "costs will typically be lower than if you start your integration by investing in enterprise service-oriented middleware products. Development costs can be especially moderate when using existing development tools that support the creation of Web services."
He also states that Web services "open the door to new integration opportunities, the quality of the interface they expose is very important. Despite being classified as a loosely coupled technology, once heavily integrated into an enterprise, many dependencies upon service interfaces can still be created. Changing an interface after it has been established can be a costly (and messy) task, especially in environments that utilize service assemblies."
However, he concludes that architects that invest smartly in SOA can realize significant tangible returns. "Integration effort within a relatively standardized SOA will drop significantly," he states. "Hooking new and legacy systems into an established Web services-enabled architecture will require a fraction of the effort and cost of traditional point-to-point integration projects. There are definite and measurable returns to be had on your investment, so it pays to get it right the first time."