==== ARQ 2.1 beta

ARQ 2.1 beta is a complete implementation of SPARQL including
support for custom filter function, property functions
and free text search.  It also provides an update language
based on SPARQL.

This version introduces a new query optimizer.  We are actively seeking
feedback - please let us know if it works for you so we can move from beta to
full release.

I'd like to thank Markus for his work on the optimizer for ARQ.

== Cost-based Optimizer

The ARQ-2.1-beta release includes a static cost-based optimizer for
Basic Graph Patterns for in-memory models. The optimizer uses heuristics
to estimate the execution cost of triple patterns and reorders the patterns
of a BGP according to their estimated costs. The optimizer is enabled by
default in ARQ but may be disabled if this should be required.

Please refer to the documentation for further information.

We are actively seeking feedback about the optimizer. Please don't hesitate to
send us any comments or problems.

== Remote query support

The ARQ query language, an extension of SPARQL, includes the ability
to call a remote SPARQL service using the SERVICE form.

    SERVICE <serviceEndPoint> { pattern }

The pattern is sent to and executed at the remote service.  ARQ combines the
results with the locally part of the query.  The algebra supports a new
operation, OpService, for this.  Algebra expression can be turned back into
SPARQL query syntax.

== Links

Download:
    http://prdownloads.sourceforge.net/jena/ARQ-2.1-beta.zip
    Use jena.jar in this download - ARQ does not work with Jena.2.5.3

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/

SPARQL-Update is described in:
    http://jena.hpl.hp.com/~afs/SPARQL-Update.html

== Status

The implementation of SPARQL is complete and meets the
SPARQL current editors' working draft and Candidate Recommendation.

ARQ passes all the DAWG tests.

Latest published:
    http://www.w3.org/TR/rdf-sparql-query/

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

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

== Notes

+ The old ARQ-1 query engine "engine1" has been removed.

== Online Services

SPARQL syntax 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@...

General questions and comments on SPARQL to jena-dev or
      public-sparql-dev@...

Formal comments specific to the SPARQL query language,
protocol or result set documents to:
	 public-rdf-dawg-comments@...