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                            Rasqal RDF Query Library

Dave Beckett

Overview

   Rasqal is a free software / Open Source C library that handles Resource
   Description Framework (RDF) query syntaxes, query construction and
   query execution returning result bindings. The supported query
   languages are SPARQL and RDQL.

   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 (Unix, GNU/Linux, BSDs, OSX, cygwin) win32
   and others.

   This is a beta quality library - the code is mature but the API is
   still changing and the SPARQL support is under active development. See
   the todo list for the current state information. 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 SPARQL.
     * Query language support for RDQL.
     * Triple store querying APIs to support running 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 support
   for query languages, a query API and a result bindings API over graphs
   stored in Redland.

Supported Query Languages

  SPARQL Query Language for RDF

   Rasqal provides support for the W3C SPARQL Query Language being
   developed by the W3C RDF Data Access Working Group, as defined in
   SPARQL Query Language for RDF, W3C Proposed Recommendation 12 November
   2007. It currently implements most of the functionality except for
   GRAPH, UNION and part of OPTIONAL. For detailed information on the
   implementation state, see the Rasqal todo / bugs list and the Redland
   issue tracker.

  RDF Data Query Language (RDQL)

   Rasqal provides a complete implementation of 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 all the Jena
   RDQL test suite bar a couple. Detail of the status of the RDQL support
   is given in the Redland issue tracker.

  LAQRS Adds to Querying RDF in SPARQL (LAQRS)

   LAQRS is an experimental set of syntax extensions for SPARQL. The
   syntax and features may change at any time. At present Rasqal provides
   only parsing and API support for it.

Installation and Documentation

   The public API is described in the librasqal.3 UNIX manual page and in
   more detail in the API reference. It is demonstrated in the roqet
   utility program which shows how to call the query engine and operate
   over the query results. When Rasqal is used inside Redland, the Redland
   documentation explains how to call the query engine and contains
   several example programs.

   To install Rasqal see the Installation document.

Sources

   The packaged sources are available from
   http://download.librdf.org/source/ (master site) and also from the
   SourceForge site. The development Subversion sources can also be
   browsed with ViewCV.

   Rasqal requires Raptor 1.4.0 or newer to build and run, which can be
   downloaded from the same area as the Rasqal source and binaries.

License

   This library is free software / open source software released under the
   LGPL (GPL) or Apache 2.0 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 (C) 2003-2008 Dave Beckett
   Copyright (C) 2003-2005 University of Bristol