Rasqal is a free software/Open Source C library that handles RDF query syntaxes, query construction and query execution returning result bindings.
Rasqal was designed to work closely with the Redland RDF library but is entirely separate. It is intended to be a portable library working across many POSIX systems.
This is an beta quality library - the code and APIs are new however likely to change. See the todo list for the latest state. A summary of the changes can be found in the NEWS file, detailed API changes in the release notes and file-by-file changes in the CVS ChangeLog.
Rasqal provides:
Rasqal does not provide an RDF API or triple store, but relies on
external libraries implementing the triple store API providing matched
RDF data originally from a specified content URI.
Rasqal ships with triple store implementations using the output
of an RDF parser from
Raptor
and over a
Redland
indexed triple store.
These can be called using the standalone roqet query utility giving a query language
identifier and query string to run the query over content
described inside the query string (in RDQL, the FROM clause).
Rasqal also works inside Redland (0.9.17 or newer) to provide query language support, query API and result bindings API over graphs stored in Redland.
Rasqal provides a syntax parser and query constructor for the RDQL language, as defined in RDQL - A Query Language for RDF, W3C Member Submission 9 January 2004 based on the earlier versions in Jena defined in RDQL RDF Data Query Language and the RDQL Grammar. The Jena RDQL Tutorial gives an introduction on the language. Rasqal currently passes the majority of the Jena RDQL test suite. Further explanation on the tests not passed are given in the Rasqal todo / bugs list.
The public API is described briefly in the librasqal.3 UNIX manual page and in more detail in the API reference.
The packaged sources are available from http://www.redland.opensource.ac.uk/dist/source/ (master site) and also from the SourceForge site. There are nightly snapshots of the development version which is can also be browsed via CVSweb. Binary packages of Rasqal and related libraries are available from the download area.
This library is free software / open source software released under the LGPL or MPL licenses. See LICENSE.html for full details.
The Redland mailing lists discusses the development and use of Rasqal and Redland as well as future plans and announcement of releases.
Copyright 2003-2004 Dave Beckett, Institute for Learning and Research Technology, University of Bristol