SOA governance, tragically, is DOA.
Still, enterprise IT groups rarely turn on a dime, and they don't lightly abandon technology investments and strategic decisions. When asked if their SOA projects have been successful in delivering a positive business impact, respondents overwhelmingly say results were as expected. Both positive and negative extremes ("more successful" and "less successful") rate nearly identical low scores. One interpretation: It's human nature to resist admitting mistakes, so these IT pros are reluctant to cede defeat. But our take--supported by survey results and discussions with a wide range of stakeholders--is that many companies are moving forward with SOA implementations, though a significant number have decided to shift course and take the path of least resistance. In essence, that means building their SOAs on the Web, using Internet-delivered APIs, and swapping in more agile REST-based Web services as a simpler alternative to heavyweight SOAP-based Web services where appropriate. In fact, when asked to indicate their past, present, and estimated future use of SOAP-based Web services vs. REST-based Web services, respondents show a marked drop-off in use of SOAP, from 54% a year ago to a projected 42% in the next 18 months. The number primarily using or considering REST-based Web services is predicted to grow by a proportional amount, from 14% to 24% over the same time frame.
The REST philosophy has simplicity going for it, and when resources get tight, faster and easier usually wins. However, the two styles can complement each other; it doesn't have to be a case of one or the other. A REST-based approach is a natural for data-oriented applications that focus on simple database look-up scenarios. Many apps fit this model, especially on the Web. Another explanation for the increasing popularity of REST is the growing number of rapid prototyping tools, such as Ruby on Rails, that can be used to build these types of apps.
REST isn't the best solution for all Web services, of course. Our advice: Don't be married to one method or the other. To simplify your application development process and make it more accessible to more people, first consider REST for straightforward operations. Choose SOAP only when your requirements demand it, as with applications that require complex data retrieval operations or network independence. Here SOAP is the more viable option.
An example of an IT pro taking this balanced approach is Ernest Mueller, whose company has experienced rapid growth of its internal all-SOAP SOA implementation. Mueller manages the Web systems team at National Instruments, a supplier of measurement and automation products for engineers and scientists. Two years ago, as part of a business/technology alignment effort, Meuller and a multidiscipline Web architecture team identified two major areas in which NI needed consistent, reusable systems.
Based on these needs, the team selected Oracle's SOA Suite as its platform. Mueller says that while NI's SOA project has been slow to define standards and governance--a trend in our poll--the company is happy overall with its SOAP implementation internally. However, the team is looking at REST as NI starts to expose services externally, thanks to what Mueller sees as REST's better ease of use.