
                           Rasqal RDF Query Library

Dave Beckett
Institute for Learning and Research Technology
University of Bristol

Overview

   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:
     * An RDF query construction and access API.
     * A query execution engine including constraint expression evaluation.
     * A query result binding API.
     * Query language support for RDQL.
     * Triple store querying APIs to support querying over external RDF graphs.
     * No memory leaks.
     * roqet standalone RDF query utility program

   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.

Supported Query Languages

  RDF Data Query Language (RDQL)

   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.

Installation and Documentation

   The public API is described briefly in the librasqal.3 UNIX manual page and
   in more detail in the API reference.

Sources

   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.

License

   This library is free software / open source software released under the LGPL
   or MPL licenses. See LICENSE.html for full details.

Mailing Lists

   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
