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.
Raptor is a C library providing a set of parsers and serializers for Resource Description Framework (RDF) triples by parsing syntaxes into RDF triples and serializing triples into a syntax. The parsers support RDF/XML, N-Triples, GRDDL, and Turtle, and via RSS tag soup: XML RSS, Atom 0.3, and Atom 1.0. The serializers support RDF/XML (3 flavours), Turtle, DOT, N-Triples, RSS 1.0, and Atom 1.0. Raptor handles RDF/XML as used by RDF applications such as RSS 1.0, FOAF, DOAP, Dublin Core, and OWL. It can use either expat or libxml2 for XML parsing, libcurl when available for URI retrieval, and is portable to many POSIX systems.
Rasqal is a C library for querying RDF graphs, supporting the SPARQL, RDQL, and LAQRS languages. It provides APIs for creating a query and parsing query syntax. It features pluggable triple-stores and matching interfaces, query engines for executing the queries, an API for manipulating results as bindings, and multiple ways to format the results to XML, CSV, TSV, and JSON. It uses the Raptor RDF parser to return triples from RDF content, and can alternatively work with the Redland RDF library's persistent triple stores. It is portable across many POSIX systems.
Graffiti is an RDF store based on dynamic translation of RDF queries into SQL. It allows you to map any relational database schema into RDF semantics and vice-versa, and to store any RDF data in a relational database. Since 2003, this RDF store was used as the primary means of data access in the Samizdat open publishing engine, and now it's released as a stand-alone module ready for use in other applications.
4store is an efficient, scalable, and stable RDF database. It was developed to underpin Semantic Web applications. It has been providing a base platform for these applications for around 3 years. It has successfully held and run queries over databases of 15GT, supporting a Web application used by hundreds of thousands of people.
Morla is an editor of RDF documents that allows you to manage more RDF documents simultaneously, visualize graphs, and use templates for quick writing. You can import RDFS documents and use their content to write new RDF triples. Templates are also RDF documents, and they make Morla easily personalizable and expandable. You can also use Morla as an RDF navigator, browsing the RDF documents present on the Internet exactly as you are used to doing with normal browsers.