This book constitutes the refereed proceedings of the 20th International Conference on Database and Expert Systems Applications, DEXA 2009, held in Linz, Austria, in August/September 2009.

Invited Talk.- Management of Information Supporting Collaborative Networks.- XML and Databases I.- A Low-Storage-Consumption XML Labeling Method for Efficient Structural Information Extraction.- Inclusion Dependencies in XML: Extending Relational Semantics.- The Real Performance Drivers behind XML Lock Protocols.- XML and Databases II.- XTaGe: A Flexible Generation System for Complex XML Collections.- Utilizing XML Clustering for Efficient XML Data Management on P2P Networks.- On the Termination Problem for Declarative XML Message Processing.- Web, Semantics and Ontologies I.- Consistency Checking for Workflows with an Ontology-Based Data Perspective.- Conceptual and Spatial Footprints for Complex Systems Analysis: Application to the Semantic Web.- Automatic Extraction of Ontologies Wrapping Relational Data Sources.- Temporal, Spatial, and High Dimensional Databases (Short Papers).- A Query Cache Tool for Optimizing Repeatable and Parallel OLAP Queries.- Efficient Map Portrayal Using a General-Purpose Query Language.- On Low Distortion Embeddings of Statistical Distance Measures into Low Dimensional Spaces.- Real-Time Traffic Flow Statistical Analysis Based on Network-Constrained Moving Object Trajectories.- Invited Talk.- Data Management for Federated Biobanks.- Web, Semantics and Ontologies II.- Peer-to-Peer Semantic Wikis.- VisiNav: Visual Web Data Search and Navigation.- Diagnosing and Measuring Incompatibilities between Pairs of Services.- Database and Information System Architecture, Performance and Security (Short Papers).- Scaling-Up and Speeding-Up Video Analytics Inside Database Engine.- Experimental Evaluation of Processing Time for the Synchronization of XML-Based Business Objects.- SimulPh.D.: A Physical Design Simulator Tool.- Protecting Database Centric Web Services against SQL/XPath Injection Attacks.- Reasoning on Weighted Delegatable Authorizations.- Web, Semantics and Ontologies III.- Annotating Atomic Components of Papers in Digital Libraries: The Semantic and Social Web Heading towards a Living Document Supporting eSciences.- Web Navigation Sequences Automation in Modern Websites.- Supporting Personal Semantic Annotations in P2P Semantic Wikis.- XML and Databases III (Short Papers).- OrdPathX: Supporting Two Dimensions of Node Insertion in XML Data.- XQSuggest: An Interactive XML Keyword Search System.- A Prüfer Based Approach to Process Top-k Queries in XML.- Bottom-Up Evaluation of Twig Join Pattern Queries in XML Document Databases.- Query Rewriting Rules for Versioned XML Documents.- Querying XML Data with SPARQL.- Query Processing and Optimization I.- Progressive Evaluation of XML Queries for Online Aggregation and Progress Indicator.- Dynamic Query Processing for P2P Data Services in the Cloud.- A Novel Air Index Scheme for Twig Queries in On-Demand XML Data Broadcast.- Semantic Web and Ontologies IV (Short Papers).- Semantic Fields: Finding Ontology Relationships.- Complete OWL-DL Reasoning Using Relational Databases.- FRESG: A Kind of Fuzzy Description Logic Reasoner.- Extracting Related Words from Anchor Text Clusters by Focusing on the Page Designer's Intention.- Invited Talk.- Evolution of Query Optimization Methods: From Centralized Database Systems to Data Grid Systems.- Query Processing and Optimization II.- Reaching the Top of the Skyline: An Efficient Indexed Algorithm for Top-k Skyline Queries.- Energy Efficient and Progressive Strategy for Processing Skyline Queries on Air.- RoK: Roll-Up with the K-Means Clustering Method for Recommending OLAP Queries.- Query Processing and Optimization III.-On Index-Free Similarity Search in Metric Spaces.- An Approximation Algorithm for Optimizing Multiple Path Tracking Queries over Sensor Data Streams.- Data and Information Integration and Quality.- A Versatile Record Linkage Method by Term Matching Model Using CRF.- On-the-Fly Integration and Ad Hoc Querying of Life Sciences Databases Using LifeDB.- Analyses and Validation of Conditional Dependencies with Built-in Predicates.- Data Mining and Knowledge Extraction (Short Papers).- Discovering Sentinel Rules for Business Intelligence.- Discovering Trends and Relationships among Rules.- Incremental Ontology-Based Extraction and Alignment in Semi-structured Documents.- Tags4Tags: Using Tagging to Consolidate Tags.- Data and Information Streams.- Detecting Projected Outliers in High-Dimensional Data Streams.- Significance-Based Failure and Interference Detection in Data Streams.- Incremental and Adaptive Clustering Stream Data over Sliding Window.- Data Mining Algorithms.- Alignment of Noisy and Uniformly Scaled Time Series.- Extracting Decision Correlation Rules.- Maintaining the Dominant Representatives on Data Streams.- Data and Information Modelling.- Modeling Complex Relationships.- Intuitive Visualization-Oriented Metamodeling.- Information Retrieval and Database Systems (Short Papers).- PISA: Federated Search in P2P Networks with Uncooperative Peers.- Analysis of News Agencies' Descriptive Features of People and Organizations.- Analyzing Document Retrievability in Patent Retrieval Settings.- Classifying Web Pages by Using Knowledge Bases for Entity Retrieval.- Terminology Extraction from Log Files.- Database and Information System Architecture and Performance.- Evaluating Non-In-Place Update Techniques for Flash-Based Transaction Processing Systems.- A RelationalEncoding of a Conceptual Model with Multiple Temporal Dimensions.- Three Approximation Algorithms for Energy-Efficient Query Dissemination in Sensor Database System.- Query Processing and Optimization IV (Short Papers).- Top-k Answers to Fuzzy XPath Queries.- Deciding Query Entailment in Fuzzy Description Logic Knowledge Bases.- An Optimization Technique for Multiple Continuous Multiple Joins over Data Streams.- Top-k Queries with Contextual Fuzzy Preferences.- Reranking and Classifying Search Results Exhaustively Based on Edit-and-Propagate Operations.