SAP XI
Followings are some online resources on the subject of SAP XI or SAP PI :
SAP Exchange Infrastructure (XI)
Adapter Framework , which is also based on the SAP XI Adapter Engine. The adapter framework is based on the SAP J2EE Engine (part of the SAP Web Application Server) and the J2EE Connector Architecture (JCA).
Receiver JMS adapter . The receiver adapter supports system acknowledgments but not application acknowledgments.