This part of the series discussed some interoperability problems caused by XML namespace conflicts. Still, the namespace conflicts in the interacting Web services do not end here. There are many more scenarios, both subtle and rare, but it happens. Namespace conflicts are difficult to fix when hundreds of Web services are deployed in a large corporation environment. When writing Web services, the best practice is to anticipate and avoid the potential conflicts on a different platform. IBM WebSphere Studio Application Developer Integration Edition also provides a powerful refactoring tool. If naming conflicts indeed occur during the integration, the tool can help you to refactor.

This series of tips discusses a number of important issues that can challenge Web services interoperability across platforms and offers best practices, particularly in the use of XML Schema types, namespaces, and Web services interface bindings. With many years of joint efforts by WS-I members, Web services interoperability is achievable. As vendors' IDE tools mature, the integration will get even better. But it's not realistic to think that some day all of Web services will interact with just a few mouse clicks, even with the help of the most sophisticated and powerful IDE tools. After all, Web services are developed on heterogeneous platforms. Even if everyone is coding to the same WS-I specifications, there will be mismatches, misinterpretations, and different conventions. In the production field, there are many more interoperability issues that need to be considered by human engineers. Some of the important interoperability topics are:

• Error handling: It is very important to anticipate different error conditions and types of faults that can occur and can be returned by the communicating parties, and to define those wsdl:faults as part of wsdl:operations in the WSDL.
• Security interoperability: Web services calls need to be signed and encrypted (WS-Security). The capability to perform vendor-neutral and transport-independent security for Web services is the goal of WS-Security and is an important step in Web services integration in a production environment.

I will discuss those other interoperability topics in future tips.