The RDF version of SIFTS is now available at our FTP site ftp://ftp.pdbj.org/RDF/sifts/. SIFTS provides various annotations of protein sequences in the PDB such as the Gene Ontology, taxonomy (biological species), structural classifications (SCOP and CATH), enzyme codes, and correspondence with UniProt sequences, and its RDF version facilitates the integration of these data with RDF data from diverse sources by using the semantic web technologies.