SOA isn’t just trendy, it’s here and it’s working. Most large enterprises have already launched some sort of SOA initiative, the objective being an agile architecture that can respond to business needs in near-real time. Along the way, SOA provides a means for fixing systems that have languished in a dysfunctional state for years. No wonder IDC expects spending on SOA-related software to reach nearly $15 billion by 2009.

With an SOA in place, organizations can leverage existing systems in a dynamic environment, abstracting the essence of applications into services that can be reassembled quickly into new solutions. But how do you get there from here? An SOA has so many moving parts, it’s often difficult to step back and isolate the guiding principles that can keep an initiative heading toward success.

Fortunately, with so much SOA activity out there, the lessons of experience are plentiful. In fact, you can count the most important of those on one hand: understand the pain, define the value, focus on understanding, remember the people, and concentrate on the long term.

Understand the pain

In many modern global 2000 companies, existing enterprise architectures hinder the business’s ability to change. For instance, a recent survey by the Business Performance Management Institute found that only 11 percent of executives say they’re able to keep up with business demand to change technology-enabled processes -- 40 percent of which are currently in need of IT attention.

Worse, according to a poll conducted by CIO magazine, 36 percent of respondents reported that their company’s IT departments are having either “significant difficulties” (27 percent) or “can’t keep up at all” (9 percent).

The reality is that IT has suffered dire levels of latency in supporting business changes. CEOs pull out their hair when IT talks about years rather than months to accommodate new product lines, markets, or mergers. Indeed, in many companies, the IT shop is the single limiting factor in business success, and it can kill the business if left to continue as is.

This is real pain … and a real problem. Solving this problem can be a tremendous boon for many organizations. Never forget that responsiveness is the main driver -- and the principal benefit -- of SOA.

Define the value

Organizations implement SOA for two major reasons. The first reason is to gain the ability to save development dollars through reuse of services. These services may have been built inside or outside of the company, and the more services that are reusable from system to system, the greater the ROI. The second reason is the ability to change IT infrastructure faster and adapt to shifting needs of the business. This provides a huge strategic advantage and can give the business a better chance of survival in the long-term.

Several factors can help you quantify the value of service reuse, including the number of services that are reusable, the complexity of those services, and the degree of reuse from system to system. The complexity of each service is key to assessing value, which can be defined as the number of functions or object points that make up the service. Just as important is the number of instances where you expect it will be practical to reuse a given service.