Hi Matias,
In mid May you will find Ariba Sourcing integartion with SAP ERP in an updated version of the Ariba solution integration for SAP Business Suite rapid-deployment solution (RDS) at http://service.sap.com/public/rds-ariba. It uses SAP NetWeaver PI with the Ariba Cloud Integration adapter (CI-6 or higher) as prerequisite middleware. The RDS package guides you step by step through the implementation. Intended release day is May 12.