Invited Talks -- Tools and Techniques in Qualitative Reasoning about Space -- A Simple but Formal Semantics for XML Manipulation Languages -- Algorithmic Definability and Completeness in Modal Logic -- Regular Articles -- A Probabilistic Temporal Logic That Can Model Reasoning about Evidence -- An Algorithm for Generating Nash Stable Coalition Structures in Hedonic Games -- Conjunctive Queries with Constraints: Homomorphism, Containment and Rewriting -- Enhancing Dung’s Preferred Semantics -- On the Distance of Databases -- On the Existence of Armstrong Data Trees for XML Functional Dependencies -- Polymorphism in Datalog and Inheritance in a Metamodel -- Possibilistic Semantics for Logic Programs with Ordered Disjunction -- Semantic Web Search Based on Ontological Conjunctive Queries -- Semantically Characterizing Collaborative Behavior in an Abstract Dialogue Framework -- The Relationship of the Logic of Big-Stepped Probabilities to Standard Probabilistic Logics -- Theoretical Foundations for Enabling a Web of Knowledge -- Towards Controlled Query Evaluation for Incomplete First-Order Databases -- Bagging Decision Trees on Data Sets with Classification Noise -- Evolving Schemas for Streaming XML -- ONTO-EVO A L an Ontology Evolution Approach Guided by Pattern Modeling and Quality Evaluation -- Towards a Paradoxical Description Logic for the Semantic Web -- Towards a Unified Model of Preference-Based Argumentation -- Two Complementary Classification Methods for Designing a Concept Lattice from Interval Data.

This volume constitutes the thoroughly refereed post-conference proceedings of the Sixth International Symposium on Foundations of Information and Knowledge Systems (FoIKS 2010) which was held in Sofia, Bulgaria, in February 2010. The 19 revised full papers presented together with three invited talks were carefully reviewed and selected from 50 papers.