Towards a Service Based Internet : 4th European Conference ServiceWave 2011 Poznan Poland October 26 28 2011. Proceedings This volume constitutes the refereed proceedings of the Fourth European Conference ServiceWave 2011 held in Poznan Poland in October 2011. The 25 revised full papers presented together with 3 invited presentations were carefully reviewed and selected from numerous submissions. They are organized in topical sections on cloud computing security privacy and trust service engineering fundamentals business services and FI PPP. In addition to the scientific track 14 extended abstracts of demonstrations covering a wide spectrum of technology and application domains were accepted.