XI Connectors

Hello everybody, we need to integrate process with backends systems such as:

FourJs

Genero

R4gl

can anyone tell me about if there's connectors to integrate this systems via SAP XI??, we are not going to implement a SAP solution such as R/3 or BW, right now we only want to use SAP Netweaver and the SAP Portal as our platform, but we are thinking of a future migration to SAP R/3, can anyone tell me about how this connectors work and where can I find documentation about it, thanks in advance.

Regards

Julio Cesar