Resource Description Framework is a W3 initiative toward the semantic web http://www.w3.org/RDF/
Redland is a library that provides a high-level interface for RDF allowing the RDF graph to be parsed from XML, stored, queried and manipulated. Redland implements each of the RDF concepts in its own class via an object based API, reflected into the other language APIs - Perl, Python, Tcl, Java and Ruby. Some of the classes providing the parsers, storage mechanisms and other elements are built as modules that can be added or removed as required. See http://www.redland.opensource.ac.uk/docs/tcl.html
SC As part of CANTCL and more recently giggle I've built a simple RDF triple store [L1 ] which stores things in a metakit database. Currently this supports only the most trivial of RDF-like applications but it will grow as I use it some more. Note this doesn't parse any RDF serialisation, it just stores triples.