SOA Development - Service Versioning Policies Page - 3

Service Versioning Policies

In this chapter, Advasco runs into the challenge of modifying an existing service. While the initial version of a service is typically developed in lock step with one or more consumers, the hopes for synchronized schedules quickly fade away when a service has two or more consumers. As shown in the narrative, there are many different ways of addressing this challenge. What is consistent, however, is that the SOA governance effort must establish policies that are consistent with the behavior desired for the company's SOA efforts.

For at least two of the options presented in Spencer's original decision-making meeting for the Customer Information Service, attendees stated that a particular option would undermine the goals of the SOA effort. One option called for the annuity team to simply write their own version of the service that they would use. This went against the goal of having no two systems implementing the same logic. It also went against the goal of having a single owner for each service capability. Another option called for the service team to maintain an arbitrary number of service implementations. While this went along with the single ownership policy, it still ended up with multiple implementations of the same logic.

We were also presented with potentially conflicting goals. Having multiple versions of the service owned by a single team results in multiple implementations, but having a single implementation that was slow and difficult to change would go against the goals of agility for the organization. In the end, the Center of Excellence recognized that agility was the more important goal, and as long as the number of versions was kept to a small number, the associated overhead on the service team was worth it.

This example demonstrates a very important point. While an organization may initially set some very high level goals and behaviors, such as decreasing the time required to deliver new business capabilities by 10%, these goals must trickle down to finer-grained policies such as the number of services that will be maintained in production.