Must the Service Type be consistent

Is it architecturally important for the service type to be consistent across the system? This is an important decision to make as if it does then it is likely you will need to select SOAP unless all you are carrying out are simple CRUD or stateless operations.

However, if a mix of service types is permitted then that allows a lot of flexibility and can vastly reduce the effort in implementing the whole system. A choice that is often made in systems where a mixture of service types are permitted, is to use REST for simple read operations and to use SOAP for the complex operations and operations where data changes may occur.