Library Techlogy Reports (vol. 48, . 4) This issue of Library Techlogy Reports presents an overview of current developments in Semantic Web techlogy that provide the foundations for making library data accessible on the Semantic Web. Author Karen Coyle introduces basic Semantic Web concepts and then describes the metadata activities and developer tools that are being used to create Semantic Web applications. She points readers to projects within and beyond the library community that are a source of metadata elements and controlled vocabularies. For software developers, she describes available software tools in the nascent world of linked data and the Semantic Web.