Web Services Programming Tips and Tricks: Use collection types with SOAP and JAX-RPC

"It is quite common for applications to manipulate collections of objects, passing them as arguments to functions and returning them when the processing is complete. There are many ways to represent these collections in most programming languages. They can be expressed as ordered vectors, unordered groups, linked lists, trees, graphs or other forms that the programming language supports. The Java language provides an entire library of collection types in the java.util package. The question, however, is how should you pass collections across a Web services invocation?"
http://www.ibm.com/developerworks/webservices/library/ws-tip-coding/index.html