This book constitutes the thoroughly refereed post-proceedings of the 4th International Workshop on Semantics in Data and Knowledge Bases, SDKB 2010, held in Bordeaux, France in July 2010. The 6 revised full papers presented together with an introductory survey by the volume editors were carefully reviewed and selected during two rounds of revision and improvement. The papers reflect a variety of approaches to semantics in data and knowledge bases.
