What if you built a service-oriented architecture and nothing got reused? Is it still of value to the business, or is it a flop?
Reuse may be the means, but not the end
Ask many experts, and the answer will be a straightforward, yes, SOA will deliver value to the business in multiple ways beyond reuse of services. (Others will say it doesn't, but that's a subject for many other posts.) Decreased infrastructure redundancy and increased time to market are two big areas where SOA has potential to deliver.
However, there are three sticky questions around reuse: First, should reuse be a goal in itself, or does it play more of a supporting role to more business-focused higher-level benefits? Is it like trying to measure the number of times employees open up Excel spreadsheets through the day, versus measuring the insights and actions they take as a result of the data they get out of their spreadsheets?
The second question is even more vexing: is reuse even essential at all to SOA success? Suppose there are services that are only used by one application each? These services may offer streamlined interfaces that provide independence from the application underneath, saving countless hours of toil and disruption when the app changes.
Third, suppose business units across the enterprise go wild with reuse, to the point where it gets difficult to track who is using what and how often? The SOA appears to be a raging success, but how is it helping the business? Is it amounting to anything? Is so, how can that be measured?
AMR's Ian Finley said too much emphasis is being put on reuse as a value driver, as observed in a follow-up interview on AMR's recent SOA study: Another danger seen from the SOA survey is that the main benefit that the vendors sell around SOA — code reuse — is not the real benefit that early SOA adopters have gotten. Often the code from project A is irrelevant to project B.... That focus on reuse can cause organizations to dismiss SOA’s benefits because they’re looking at the wrong metric."
Dave Linthicum has been warning companies against adoption of reuse as a value metric for some time. Most recently, in response to Finley's statement, he bluntly added:
"The core issue is that reuse, as a notion, is not core to the value of SOA…never has, never will. Not that you won't achieve reuse, and that there is benefit, but that the value of agility, or creating an architecture that's changeable around the needs of the business is far more valuable than any services you can share. To the point of this post, people chase SOA understanding that reuse is the core value. Thus, when it's not they consider SOA a failure.... We need to stop selling reuse as a core benefit of SOA."
James Taylor, who has been blogging prolifically from Dialog 08, reports that he had a chance to break bread with IBM's Sandy Carter and ILOG's Pierre Haren, and the subject of service reuse came up.
James notes that Pierre said that the main value of SOA today is in collaboration and understanding not in reuse. Sandy, who had some examples of customers getting a lot of reuse, "generally supported Pierre’s point, that reuse is not essential to the SOA value proposition. After all, many previous architectures promised reuse and it never seems to get delivered."
The consensus appears to be that "reuse may well come, whether through reused services or reused rules between services, but the power of SOA to bridge the business and IT is key," James observes. The question becomes how to measure the impact of that bridge.