Basically there is no real difference. It is just about marketing name of same products. SAP PI or XI is SAP NetWeaver based technology for Enterprise Application Integration (EAI). EAI software enables different systems to communicate each other. This cover systems within same organization or systems of external parties. That type of software is so called Integration Brokers as they are mediates between entities with varying requirements in terms of connectivity, format, and protocols. It provides common repository for all interfaces. Central component of XI/PI is the SAP Integration Server, which facilitates interaction between diverse operating systems and applications across internal and external networked computer systems.
When was SAP XI/PI introduced into the market and how it all began? There was always a demand for integration software within SAP’s costumers and always lack of it on SAP side. Since SAP had no strong experience within integration software they teamed up with WebMethods Company (in 2009 acquired by Software AG) and introduced SAP Business Connector (known as SAP BC). This happened around year 2000. SAP BC was branded version of webMethods Integration Server as a middleware solution for SAP R/3. In 2002 joined team were split and both companies continues to develop their product lines independently. SAP released SAP BC version 4.7. Approximately at same time SAP as having experience learned with SAP BC started with own integration / middleware product called Message Broker. This was renamed later to SAP Exchange Infrastructure (XI). Later (around year 2006) within SAP NetWeaver the name was changed from XI 3.0 to SAP Process Infrastructure (PI 7.0).
What is future of PI? Actually it is been little bit cloudy. Gartner and other analysts are saying that SAP’s statements about PI are clumsy and therefore they do not advise costumers to use it for strategic projects. This was strengthening even more by SAP’s acquisition of SOALogix. Therefore for sure there will be changes in PI as integration of BPM software is never easy. But SAP says that they are strongly committed to SAP PI.
Something about SAP: SAP PI vs. XI