   #DOAP

                            Rasqal RDF Query Library

Dave Beckett

Overview

   Rasqal is a free software / Open Source C library that handles Resource
   Description Framework (RDF) query language syntaxes, query construction
   and execution of queries returning results as bindings, boolean, RDF
   graphs/triples or syntaxes. The supported query languages are SPARQL
   1.0, RDQL, Draft SPARQL Query 1.1, Update 1.1 Syntax and Experimental
   SPARQL extensions (LAQRS). Rasqal can write binding query results in
   the SPARQL XML, SPARQL JSON, CSV, TSV, HTML, ASCII tables and Turtle
   and read them in SPARQL XML.

   Rasqal was designed to work closely with the Redland RDF library and
   the Raptor[2] RDF Syntax Library but is entirely separate from both.

   This is a beta quality library - the code is mature but the API is
   still changing and the SPARQL support is under development. It is a
   portable library and has been tested on multiple POSIX systems and
   architectures. Rasqal has no known memory leaks.

   A summary of the changes can be found in the NEWS file and detailed API
   changes in the release notes.

   Rasqal provides:
     * An RDF query construction and access API.
     * Query language support for SPARQL.
     * Query language support for RDQL.
     * A query execution engine including grouping, aggregate expression
       and filtering evaluation.
     * A query result binding API.
     * Query result bindings formatting into SPARQL XML, SPARQL JSON, CSV,
       TSV, HTML and ASCII tables and from SPARQL XML.
     * Triple store querying APIs to support running over external RDF
       graphs.
     * No memory leaks.
     * roqet standalone command line 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 a
   triple store implementation using the output of an RDF parser from
   Raptor. This can be called using the standalone command line roqet
   query utility giving a query language identifier (default sparql), the
   query string and optionally the data to use unless it is declared in
   the query string.

   Rasqal is used inside Redland to provide support for query languages, a
   query API and a result bindings API over graphs stored in indexed
   Redland triple stores. Since this can index the triples it will be
   faster than the default rasqal triple store of reading the triples from
   Raptor into memory when the queries are complex.

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
   UNION. For detailed information on the implementation state, see the
   Rasqal bugs in the Redland issue tracker. It also implements some of
   the SPARQL 1.1 Query and SPARQL 1.1 Update W3C working drafts of 14
   October 2010.

  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. 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 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 build and install Rasqal from sources 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 GIT sources can also be browsed on
   GitHub or checked out at git://github.com/dajobe/rasqal.git

   Rasqal requires Raptor 1.4.19 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) 2003-2010 Dave Beckett
   Copyright (C) 2003-2005 University of Bristol
