Hello Rebecca,
As far as I know, the execute_asynchronous/synchronous method has been removed in PI 7.1 and above. The method name should have the same as the name of your service interface (if you choose Stateless XI-Compatible). In Stateless, you can rename the method as you wish.
The calling of the method would be the same, except that you don't use execute_asynchronous/synchronous anymore.
Hope this helps,
Mark