This book constitutes the refereed proceedings of the 5th European Semantic Web Conference, ESWC 2008, held in Tenerife, Canary Islands, Spain, in June 2008.

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.