ChangeLog for ARQ
=================

ARQ 2.0
-------

This version uses the SPARQL algebra directly,
then produces an execution scheme that uses streaming
execution where possible.

+ SPARQL changes
  + Prefixed names can now start with a digit.  ex:123 is now a legal prefix name.
  + The working group has removed attributes "ordered" and "distinct" from the
    XML Results format. These have been removed in this release.  ARQ will read
    old style XML files (and ignore the attributes).

+ Multiple query engines:
  + 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.
  + Engine1, for exact ARQ1 semantics and enhancements
    (deprecated for new applications (and will be removed sometime))
  + RDQL engine
  + See also SDB - an ARQ query engine that for RDF stored in SQL databases 

+ Access and extension points:
   + Filter functions
   + Property functions
   + The parsed syntax
   + Generation of the SPARQL algebra expression
     + Modification of SPARQL algebra expression before executin plan generation
     + Custom algebra operations 
   + Basic graph pattern replacement or modification
     for access to other data sources
   + Modular query engine class hierarchy for reuse of machinary,
     resulting in less extra coding for extensions.
 
 + Internal changes
   + Package reorganisation
     Implemnentation in com.hp.hpl.jena.sparql
   + Filter functions now take a Context, not an ExecutionContext.
   + Deprecate "EXT" form from ARQ.
     (Property functions are better)
     
 + Experimental SPARQL/Update API
   See http://jena.hpl.hp.com/~afs/SPARQL-Update.html

Post ARQ-2.0-beta: 
+ Added REDUCED as per DAWG decision 2007-03-20
+ OpDistinct and OpReduce no longer take a variable list
+ Removed ElementExtension/PlanExtension and extension package
  The ARQ(beyond SPARQL feature) of "EXT" has been removed.
  Element visitors may be affected.
+ Added an update API
+ LARQ
	+ added access to the match score
	+ added limits on score or number of results as part of Lucene search