Constitutes the refereed postproceedings of the Second International Workshop on Semantic Web and Databases, held in Toronto, Canada in August 2004 as a satellite workshop of VLDB 2004. This work discusses various topics including, data semantics, semantic Web services, service-oriented computing, workflow composition, and XML semantics.

Service Oriented Computing: Opportunities and Challenges.- Data Semantics Revisited.- Dynamic Agent Composition from Semantic Web Services.- Ontology-Extended Component-Based Workflows : A Framework for Constructing Complex Workflows from Semantically Heterogeneous Software Components.- Data Procurement for Enabling Scientific Workflows: On Exploring Inter-ant Parasitism.- XSDL: Making XML Semantics Explicit.- Refining Semantic Mappings from Relational Tables to Ontologies.- Triadic Relations: An Algebra for the Semantic Web.- Semantically Unlocking Database Content Through Ontology-Based Mediation.- Representation and Reasoning About Changing Semantics in Heterogeneous Data Sources.- Context Mediation in the Semantic Web: Handling OWL Ontology and Data Disparity Through Context Interchange.- HCOME: A Tool-Supported Methodology for Engineering Living Ontologies.- Query Answering by Rewriting in GLAV Data Integration Systems Under Constraints.- Utilizing Resource Importance for Ranking Semantic Web Query Results.- Querying Faceted Databases.- Constructing and Querying Peer-to-Peer Warehouses of XML Resources.