Final answer:
In a BPEL process for an asynchronous request, two roles need to be defined in the Partner Link Type to facilitate the communication between the service provider and the service requester.
Step-by-step explanation:
In the context of a Business Process Execution Language (BPEL) process, when dealing with an asynchronous request, two roles need to be defined in the Partner Link Type. One role is for the service provider and the other is for the service requester. This dual-role configuration allows for asynchronous communication, where the service requester sends a message to the service provider and continues its process without waiting for an immediate response. The service provider processes the message, and at a later point in time, sends a response back asynchronously.