RDFa and GRDDL are evolving W3C standards to embed semantic markup in XHTML pages. Composer can parse such documents to extract RDFa metadata from HTML pages. The metadata can then be treated like any other RDF source, and users can perform DL reasoning or SPARQL queries on it. Together with the other data integration capabilities and visualization tools Composer can be used to develop mash-up applications. TopBraid is also a comprehensive RDFa Editor.