Book excerpt: This book constitutes the refereed proceedings of the 27th International Conference on Conceptual Modeling, ER 2008, held in Barcelona, Spain, in October 2008. The 33 revised full papers presented together with 18 demo papers were carefully reviewed and selected from 178 submissions. The papers are organized in topical sections on novel semantics; ontology; patterns; privacy, compliance, location; process management and design; process models; queries; similarity and coherence; space and time; system design; translation, transformation, and search.