Data Services are feature-rich, virtual views built across federated and heterogeneous data sources such as semi-structured sources, relational databases, and Web services. They simplify and mediate bidirectional data access and updates for business processes, portals, and applications. Data Services implement mappings and transformations, offer XQuery and SQL interfaces, secure data service functions, intelligently orchestrate query and transaction operations for the data sources, and enforce access-control policies driven by specific values of the data elements. Additional features include auditing, caching, and an Excel plug-in.