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112 lines
4.5 KiB
Plaintext
112 lines
4.5 KiB
Plaintext
#DOAP
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Rasqal RDF Query Library
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Dave Beckett
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Overview
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Rasqal is a free software / Open Source C library that handles Resource
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Description Framework (RDF) query syntaxes, query construction and
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query execution returning result bindings. The supported query
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languages are SPARQL and RDQL.
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Rasqal was designed to work closely with the Redland RDF library but is
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entirely separate. It is intended to be a portable library working
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across many POSIX systems (Unix, GNU/Linux, BSDs, OSX, cygwin) win32
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and others.
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This is a beta quality library - the code is mature but the API is
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still changing and the SPARQL support is under active development. See
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the todo list for the current state information. A summary of the
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changes can be found in the NEWS file, detailed API changes in the
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release notes and file-by-file changes in the CVS ChangeLog.
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Rasqal provides:
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* An RDF query construction and access API.
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* A query execution engine including constraint expression
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evaluation.
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* A query result binding API.
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* Query language support for SPARQL.
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* Query language support for RDQL.
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* Triple store querying APIs to support running over external RDF
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graphs.
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* No memory leaks.
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* roqet standalone RDF query utility program
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Rasqal does not provide an RDF API or triple store, but relies on
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external libraries implementing the triple store API providing matched
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RDF data originally from a specified content URI. Rasqal ships with
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triple store implementations using the output of an RDF parser from
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Raptor and over a Redland indexed triple store. These can be called
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using the standalone roqet query utility giving a query language
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identifier and query string to run the query over content described
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inside the query string (in RDQL, the FROM clause).
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Rasqal also works inside Redland (0.9.17 or newer) to provide support
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for query languages, a query API and a result bindings API over graphs
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stored in Redland.
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Supported Query Languages
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SPARQL Query Language for RDF
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Rasqal provides support for the W3C SPARQL Query Language being
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developed by the W3C RDF Data Access Working Group, as defined in
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SPARQL Query Language for RDF, W3C Proposed Recommendation 12 November
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2007. It currently implements most of the functionality except for
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GRAPH, UNION and part of OPTIONAL. For detailed information on the
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implementation state, see the Rasqal todo / bugs list and the Redland
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issue tracker.
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RDF Data Query Language (RDQL)
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Rasqal provides a complete implementation of the RDQL language, as
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defined in RDQL - A Query Language for RDF, W3C Member Submission 9
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January 2004 based on the earlier versions in Jena defined in RDQL RDF
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Data Query Language and the RDQL Grammar. The Jena RDQL Tutorial gives
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an introduction on the language. Rasqal currently passes all the Jena
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RDQL test suite bar a couple. Detail of the status of the RDQL support
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is given in the Redland issue tracker.
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LAQRS Adds to Querying RDF in SPARQL (LAQRS)
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LAQRS is an experimental set of syntax extensions for SPARQL. The
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syntax and features may change at any time. At present Rasqal provides
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only parsing and API support for it.
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Installation and Documentation
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The public API is described in the librasqal.3 UNIX manual page and in
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more detail in the API reference. It is demonstrated in the roqet
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utility program which shows how to call the query engine and operate
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over the query results. When Rasqal is used inside Redland, the Redland
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documentation explains how to call the query engine and contains
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several example programs.
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To install Rasqal see the Installation document.
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Sources
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The packaged sources are available from
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http://download.librdf.org/source/ (master site) and also from the
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SourceForge site. The development Subversion sources can also be
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browsed with ViewCV.
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Rasqal requires Raptor 1.4.0 or newer to build and run, which can be
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downloaded from the same area as the Rasqal source and binaries.
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License
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This library is free software / open source software released under the
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LGPL (GPL) or Apache 2.0 licenses. See LICENSE.html for full details.
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Mailing Lists
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The Redland mailing lists discusses the development and use of Rasqal
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and Redland as well as future plans and announcement of releases.
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__________________________________________________________________
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Copyright (C) 2003-2008 Dave Beckett
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Copyright (C) 2003-2005 University of Bristol
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