Information integration: A research agenda

The theme for this special issue-information integration-reflects the growing importance of integration in general, and data integration in particular, as a driving force in information technology spending. This essay discusses information integration along three axes-data types, federation, and intelligence. Several important problem areas are emerging-storage and retrieval of XML (Extensible Markup Language) documents, federation and distribution across data sources, and holistic intelligence across different data modalities. This special issue is devoted to papers on many of these topics, and we expect this to be an active area of research for many years to come.