java programmer-XI learning

Hi all,

I am N.Narendramohan working on java,J2ee,ematrix(2+expi) Having knowledge of ABAP also,but not CrossApplications like ALE,IDOC.

I am intrested in learning XI.but people suggests me to learn EP. which is good for me in long run?

what r the pre-requests for learning XI ?

Regards

-Narendramohan