The papers are organized in topical sections on agents, application ontologies, applications, formal languages, foundational issues, learning, ontologies and natural language, ontology alignment, query processing, search, semantic Web services, storage and retrieval of semantic Web data, as well as user interfaces and personalization.

Invited Talks.- From Capturing Semantics to Semantic Search: A Virtuous Cycle.- Foundations of RDF Databases.- Garlik: Semantic Technology for the Consumer.- Agents.- Semantic Web Technology for Agent Communication Protocols.- xOperator – Interconnecting the Semantic Web and Instant Messaging Networks.- Application Ontologies.- An Ontology for Software Models and Its Practical Implications for Semantic Web Reasoning.- A Core Ontology for Business Process Analysis.- Applications.- Assisting Pictogram Selection with Semantic Interpretation.- KonneXSALT: First Steps Towards a Semantic Claim Federation Infrastructure.- Building a National Semantic Web Ontology and Ontology Service Infrastructure –The FinnONTO Approach.- Creating and Using Geospatial Ontology Time Series in a Semantic Cultural Heritage Portal.- Semantic Email as a Communication Medium for the Social Semantic Desktop.- IVEA: An Information Visualization Tool for Personalized Exploratory Document Collection Analysis.- Building a Semantic Web Image Repository for Biological Research Images.- Formal Languages.- Mapping Validation by Probabilistic Reasoning.- Safe and Economic Re-Use of Ontologies: A Logic-Based Methodology and Tool Support.- dRDF: Entailment for Domain-Restricted RDF.- Finite Model Reasoning in DL-Lite.- Module Extraction and Incremental Classification: A Pragmatic Approach for Ontologies.- Forgetting Concepts in DL-Lite.- Foundational Issues.- An Entity Name System (ENS) for the Semantic Web.- A Functional Semantic Web Architecture.- Learning.- Query Answering and Ontology Population: An Inductive Approach.- Instance Based Clustering of Semantic Web Resources.- Conceptual Clustering and Its Application to Concept Drift and Novelty Detection.- Ontologies and Natural Language.- Enrichingan Ontology with Multilingual Information.- Rabbit: Developing a Control Natural Language for Authoring Ontologies.- A Natural Language Query Interface to Structured Information.- Distinguishing between Instances and Classes in the Wikipedia Taxonomy.- Ontology Alignment.- Two Variations on Ontology Alignment Evaluation: Methodological Issues.- Putting Ontology Alignment in Context: Usage Scenarios, Deployment and Evaluation in a Library Case.- CSR: Discovering Subsumption Relations for the Alignment of Ontologies.- Query Processing.- XSPARQL: Traveling between the XML and RDF Worlds – and Avoiding the XSLT Pilgrimage.- Streaming SPARQL - Extending SPARQL to Process Data Streams.- The Creation and Evaluation of iSPARQL Strategies for Matchmaking.- Adding Data Mining Support to SPARQL Via Statistical Relational Learning Methods.- A Semantic Web Middleware for Virtual Data Integration on the Web.- Graph Summaries for Subgraph Frequency Estimation.- Querying Distributed RDF Data Sources with SPARQL.- Improving Interoperability Using Query Interpretation in Semantic Vector Spaces.- Search.- Hybrid Search: Effectively Combining Keywords and Semantic Searches.- Combining Fact and Document Retrieval with Spreading Activation for Semantic Desktop Search.- Q2Semantic: A Lightweight Keyword Interface to Semantic Search.- Semantic Web Services.- Conceptual Situation Spaces for Semantic Situation-Driven Processes.- Combining SAWSDL, OWL-DL and UDDI for Semantically Enhanced Web Service Discovery.- Web Service Composition with User Preferences.- Enhancing Workflow with a Semantic Description of Scientific Intent.- WSMO Choreography: From Abstract State Machines to Concurrent Transaction Logic.- WSMO-Lite Annotations for Web Services.- Storage and Retrieval of Semantic Web Data.-Semantic Sitemaps: Efficient and Flexible Access to Datasets on the Semantic Web.- On Storage Policies for Semantic Web Repositories That Support Versioning.- User Interface and Personalization.- Semantic Reasoning: A Path to New Possibilities of Personalization.- An User Interface Adaptation Architecture for Rich Internet Applications.- OntoGame: Weaving the Semantic Web by Online Games.- Demo Papers.- SWING: An Integrated Environment for Geospatial Semantic Web Services.- Semantic Annotation and Composition of Business Processes with Maestro.- Learning Highly Structured Semantic Repositories from Relational Databases:.- Cicero: Tracking Design Rationale in Collaborative Ontology Engineering.- xOperator – An Extensible Semantic Agent for Instant Messaging Networks.- LabelTranslator - A Tool to Automatically Localize an Ontology.- RKBExplorer.com: A Knowledge Driven Infrastructure for Linked Data Providers.- Semantic Browsing with PowerMagpie.- Tagster - Tagging-Based Distributed Content Sharing.- The Web Service Modeling Toolkit.- Mymory: Enhancing a Semantic Wiki with Context Annotations.- Pronto: A Non-monotonic Probabilistic Description Logic Reasoner.- User Profiling for Semantic Browsing in Medical Digital Libraries.- SWiM – A Semantic Wiki for Mathematical Knowledge Management.- Integrating Open Sources and Relational Data with SPARQL.- Previewing Semantic Web Pipes.- Demo: Visual Programming for the Semantic Desktop with Konduit.- SCARLET: SemantiC RelAtion DiscoveRy by Harvesting OnLinE OnTologies.- ODEWiki: A Semantic Wiki That Interoperates with the ODESeW Semantic Portal.- Simplifying Access to Large-Scale Health Care and Life Sciences Datasets.- GRISINO - An Integrated Infrastructure for Semantic Web Services, Grid Computing and Intelligent Objects.-SemSearch: Refining Semantic Search.- The Combination of Techniques for Automatic Semantic Image Annotation Generation in the IMAGINATION Application.- WSMX: A Solution for B2B Mediation and Discovery Scenarios.- Conceptual Spaces in ViCoS.

This book constitutes the refereed proceedings of the 5th European Semantic Web Conference, ESWC 2008, held in Tenerife, Canary Islands, Spain, in June 2008. The 51 revised full papers presented together with 3 invited talks and 25 system description papers were carefully reviewed and selected from a total of 270 submitted papers. The papers are organized in topical sections on agents, application ontologies, applications, formal languages, foundational issues, learning, ontologies and natural language, ontology alignment, query processing, search, semantic Web services, storage and retrieval of semantic Web data, as well as user interfaces and personalization.