XI between different R/3 systems

HiAll,

I come from the ABAP development background and am new to XI. I am very clear about the NetWeaver concept/stack. Now there is a requirement of XI in order to establish connectivity between various SAP R/3 - SAP R/3 systems.

Since Im learning XI on my own, my questions are:

1) What technologies/programming languages would be used in XI in R/3-R/3 scenarios? i.e. ABAP/JAVA/XML etc?

2) Which course path shall I follow? ie. XI Technology Consultant Material or XI Development Consultant Material?

Please let me know. Any advise would be really helpful as I am not finding a way to start my preparation.

Thanks & Regards,

Shobhit