Is XI madatory for using HR Adminstrative services /forms and processes

Hi ,

We are in the process of implementing e-recruitment module to be integrated with PA.

We are using Hr administrative services and HCM processes and forms. As per SAP standards There are two types of communication destinations available (RFC & XI messages) ,. Can we transfer data from e-recruiting to hr admin services and administravite services to sap e-recruiting using RFC connection?

or is XI maditory? please suggest.

Thanks & regards,

Sreeharsha