ARQ is a query processor for Jena that implements SPARQL.

==== Announcing ARQ 2.0 beta

This is the first, and hopefully only, beta release of ARQ 2.0.
It is functionally a complete implementation of SPARQL including
support for custom filter function, property functions and
free text search.

== Changes to SPARQL

There are changes to the correct results from SPARQL queries in
this release to reflectthe new SPARQL algebra:

+ {} form scoping delimiters for filter.
  + { FILTER(?v > 3) :z : p ?v } is the same as 
     { :z : p ?v FILTER(?v > 3) }
  + Variables outsoide the group are no in scope.
    Any extraneous {} around FILTERs may cause different results.
  + Results from corner cases of doubly nested OPTIONALs change.
  
== Changes to applications
  
The function library and property function libary have both moved:
The correct base URIs are now:
    Functions: http://jena.hpl.hp.com/ARQ/function#
    Property functions: http://jena.hpl.hp.com/ARQ/property#

The code now resides in packages "com.hp.hpl.jena.sparql.function.library" and
"com.hp.hpl.jena.sparql.pfunction.library".  Old URIs using the old package
name and "java:" should work because there is a redirection left in-place.




The purpose of this beta release is to ensure migration costs from
ARQ 1.5.1 to ARQ 2.0 are as low as possible.  Please report any 
differences in behaviour, both functional and performance.

ARQ 2.0 provides the same external API as ARQ 1.5.  Internally, query
execution follows the SPARQL algebra, in development by the RDF Data
Access Working Group.  Several query engines are available:

 + Main query engine for optimization and efficient execution
 + Reference engine for checking functionality
    (implements the SPARQL evaluation semantics very simply for clarity
     and validation)
  + Remote access engine for querying SPARQL endpoints over HTTP.
  + The query engine from ARQ1, for exact ARQ1 semantics and to assist
    in migration (deprecated for new applications, it and will be removed
    sometime
  + RDQL engine
  
Internally, there has been significant reorganisation and renaming
to align with termininology of the SPARQL specification.

ARQ can also be used just SPARQL parsers, as a SPARQL algebra generator
or for spoecialised query engines.

Not in ARQ 2.0:
Extensions beyond the SPARQL syntax: UNSAID and EXT. 
OPTIONAL/!bound queries are support.

Download:
    http://prdownloads.sourceforge.net/jena/ARQ-2.0-beta.zip

Home page:
	http://jena.sourceforge.net/ARQ/

ARQ is also available via anonymous SVN:
https://jena.svn.sourceforge.net/svnroot/jena/ARQ/

SPARQL is described in:
  http://www.w3.org/TR/rdf-sparql-query/

== Notes

More details in ChangeLog.txt

== Status

The implementation of SPARQL is complete and meets the
SPARQL current editors' working draft and cu=urently planned
Last Call design.

Editors' working draft:
http://www.w3.org/2001/sw/DataAccess/rq23/rq25.html

Defition of SPARQL:
http://www.w3.org/2001/sw/DataAccess/rq23/rq25.html#sparqlDefinition


== Services

SPARQL validator: 
http://www.sparql.org/validator.html

SPARQL processor:
http://www.sparql.org/sparql.html

== Support and Questions


Comments and questions about ARQ to the Jena mailing list 
    jena-dev@groups.yahoo.com

General questions and comments on SPARQL to jena-dev or
    public-sparql-dev@w3.org
    
Formal comments specific to the SPARQL query language,
protocol or result set docuemnts to:
	public-rdf-dawg-comments@w3.org