This book constitutes the refereed proceedings of the 4th International Conference on Formal Concept Analysis, held in February 2006. The 17 revised full papers presented together with four invited papers were carefully reviewed and selected for inclusion in the book. The papers show advances in applied lattice and order theory and in particular scientific advances related to formal concept analysis and its practical applications: data and knowledge processing including data visualization, information retrieval, machine learning, data analysis and knowledge management.

Invited Lectures.- Methods of Conceptual Knowledge Processing.- An Enumeration Problem in Ordered Sets Leads to Possible Benchmarks for Run-Time Prediction Algorithms.- Attribute Implications in a Fuzzy Setting.- The Assessment of Knowledge, in Theory and in Practice.- Regular Papers.- The Basic Theorem on Preconcept Lattices.- The Tensor Product as a Lattice of Regular Galois Connections.- Two Instances of Peirce's Reduction Thesis.- Very Fast Instances for Concept Generation.- Negation, Opposition, and Possibility in Logical Concept Analysis.- A Note on Negation: A PCS-Completion of Semilattices.- Towards a Generalisation of Formal Concept Analysis for Data Mining Purposes.- Interactive Association Rules Discovery.- About the Family of Closure Systems Preserving Non-unit Implications in the Guigues-Duquenne Base.- Spatial Indexing for Scalability in FCA.- Homograph Disambiguation Using Formal Concept Analysis.- Using Concept Lattices to Uncover Causal Dependencies in Software.- An FCA Interpretation of Relation Algebra.- Spring-Based Lattice Drawing Highlighting Conceptual Similarity.- Characterizing Planar Lattices Using Left-Relations.- Automated Layout of Small Lattices Using Layer Diagrams.- Counting Pseudo-intents and #P-completeness.