Planning a web service
When creating a Web Service, you not only have to think of the task at hand, but you must also consider growth. You likely want the Web Service to be flexible; to be able to handle different types of input. Prepare the Web Service for what is probable. Developers should think bigger than the needs of a single application. Consider how you might reuse existing services, and how your services might be reused by others.
Security will likely play a larger role than it did previously with existing in-house application infrastructures using programmed links between systems; you will need to become versed in security issues.
Keep the goals of SOA in mind when designing and coding Web services: Flexibility. Reusability. Interoperability.