Redland is a set of C libraries providing a high-level API for the Resource Description Framework (RDF), allowing it to be stored, parsed, serialized, queried, and manipulated. It has an object-based, modular design and comes with detailed reference documentation and examples. Redland supports all RDF vocabularies such as FOAF, RSS 1.0, Dublin Core, DOAP, and OWL, the query languages SPARQL and RDQL, and all RDF syntaxes including Turtle, RDF/XML, RDF/JSON, RSS, Atom, RDFa, and GRDDL.
mod_auth_useragent2 is an Apache module that can be used to limit access to documents by means of the User-Agent. As an authentication method, this is really unsafe because it is easy to change the User-Agent in most browsers, but it could be used to prevent stupid bots and spiders from accessing your Web sites.