NAME

RDQL::Parser - A simple top-down LL(1) RDQL and SPARQL parser

SYNOPSIS

            

              
              
use RDQL::Parser;
my $parser = RDQL::Parser->new();
my $query = <<QUERY;
PREFIX rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#>
PREFIX rss: <http://purl.org/rss/1.0/>
       SELECT
          ?title ?link
       FROM
          <http://xmlhack.com/rss10.php>
       WHERE
   (?item, rdf:type <rss:item>)
   (?item, rss:title, ?title)
   (?item, rss:link ?link)
       QUERY;
       $parser->parse($query); #parse the query
# I.e.
$parser = bless( {
                'distinct' => 0,
                'constructPatterns' => [],
                'prefixes' => {
                                'fn' => 'http://www.w3.org/2004/07/xpath-functions',
                                'op' => 'http://www.w3.org/2001/sw/DataAccess/operations',
                                'owl' => 'http://www.w3.org/2002/07/owl#',
                                'dcq' => 'http://purl.org/dc/terms/',
                                'dc' => 'http://purl.org/dc/elements/1.1/',
                                'foaf' => 'http://xmlns.com/foaf/0.1/',
                                'rdfs' => 'http://www.w3.org/2000/01/rdf-schema#',
                                'rss' => 'http://purl.org/rss/1.0/',
                                'rdf' => 'http://www.w3.org/1999/02/22-rdf-syntax-ns#',
                                'xsd' => 'http://www.w3.org/2001/XMLSchema#',
                                'daml' => 'http://www.daml.org/2001/03/daml+oil#'
                              },
                'graphPatterns' => [
                                     {
                                       'constraints' => [],
                                       'optional' => 0,
                                       'triplePatterns' => [
                                                             [
                                                               0,
                                                               '?item',
                                                               '<http://www.w3.org/1999/02/22-rdf-syntax-ns#type>',
                                                               '<rss:item>'
                                                             ],
                                                             [
                                                               0,
                                                               '?item',
                                                               '<http://purl.org/rss/1.0/title>',
                                                               '?title'
                                                             ],
                                                             [
                                                               0,
                                                               '?item',
                                                               '<http://purl.org/rss/1.0/link>',
                                                               '?link'
                                                             ]
                                                           ]
                                     }
                                   ],
                'sources' => [
                               '<http://xmlhack.com/rss10.php>'
                             ],
                'describes' => [],
                'queryType' => 'SELECT',
                'resultVars' => [
                                  '?title',
                                  '?link'
                                ],
              }, 'RDQL::Parser' );
$parser->serialize(*STDOUT, 'N-Triples'); #print on STDOUT the RDQL query as N-Triples if possible (or an error)
            
          

DESCRIPTION

            

              
              
RDQL::Parser - A simple top-down LL(1) RDQL and SPARQL parser - see http://www.w3.org/TR/rdf-sparql-query/ and http://www.w3.org/Submission/2004/SUBM-RDQL-20040109/
            
          

CONSTRUCTORS

$parser = new RDQL::Parser;

METHODS

parse( PARSER, QUERY )

            

              
              
If use Data::Dumper(3) to actually dumpo out the content of the PARSER variable after invoching the parse() method it lokks like:
$VAR1 = bless( {
                'distinct' => 0,
                'constructPatterns' => [],
                'prefixes' => {
                                'fn' => 'http://www.w3.org/2004/07/xpath-functions',
                                'op' => 'http://www.w3.org/2001/sw/DataAccess/operations',
                                'owl' => 'http://www.w3.org/2002/07/owl#',
                                'dcq' => 'http://purl.org/dc/terms/',
                                'dc' => 'http://purl.org/dc/elements/1.1/',
                                'foaf' => 'http://xmlns.com/foaf/0.1/',
                                'rdfs' => 'http://www.w3.org/2000/01/rdf-schema#',
                                'rss' => 'http://purl.org/rss/1.0/',
                                'rdf' => 'http://www.w3.org/1999/02/22-rdf-syntax-ns#',
                                'xsd' => 'http://www.w3.org/2001/XMLSchema#',
                                'daml' => 'http://www.daml.org/2001/03/daml+oil#'
                              },
                'graphPatterns' => [
                                     {
                                       'constraints' => [],
                                       'optional' => 0,
                                       'triplePatterns' => [
                                                             [
                                                               0,
                                                               '?item',
                                                               '<http://www.w3.org/1999/02/22-rdf-syntax-ns#type>',
                                                               '<rss:item>'
                                                             ],
                                                             [
                                                               0,
                                                               '?item',
                                                               '<http://purl.org/rss/1.0/title>',
                                                               '?title'
                                                             ],
                                                             [
                                                               0,
                                                               '?item',
                                                               '<http://purl.org/rss/1.0/link>',
                                                               '?link'
                                                             ]
                                                           ]
                                     }
                                   ],
                'sources' => [
                               '<http://xmlhack.com/rss10.php>'
                             ],
                'describes' => [],
                'queryType' => 'SELECT',
                'resultVars' => [
                                  '?title',
                                  '?link'
                                ],
              }, 'RDQL::Parser' );
            
          

NOTES

            

              
              
The RDQL implementation is actually an extension of the original RDQL spec (http://www.w3.org/Submission/2004/SUBM-RDQL-20040109/)
to allow more SQL-like Data Manipulation Language (DML) features like DELETE and INSERT - which is much more close to the original rdfdb
query language which SquishQL/RDQL are inspired to (see http://www.guha.com/rdfdb).
As well as the SPARQL one....?
            
          

SEE ALSO

DBD::RDFStore(3)

http://www.w3.org/TR/rdf-sparql-query/ http://www.w3.org/Submission/2004/SUBM-RDQL-20040109/ http://ilrt.org/discovery/2002/04/query/ http://www.hpl.hp.com/semweb/doc/tutorial/RDQL/ http://rdfstore.sourceforge.net/documentation/papers/HPL-2002-110.pdf

FAQ

What's the difference between RDQL and SquishQL?

None :-) The former is a bit of an extension of the original SquishQL proposal defining a proper BNF to the query language; the only practical difference is that triple patterns in the WHERE clause are expressed in a different order s,p,o for RDQL while SquishQL uses '(p s o)' without commas. In addition the URIs are expressed with angle brackets on RDQL while SquishQL do not. For more about differences between the two languages see http://rdfstore.sourceforge.net/documentation/papers/HPL-2002-110.pdf

Is RDQL::Parser compliant to RDQL BNF?

Yes

Is RDQL::Parser compliant to SquishQL syntax ?

Not yet :)

What are RDQL::Parser extensions to RDQL BNF?

RDQL::Parser leverage on RDFStore(3) to run proper free-text UTF-8 queries over literals; the two main extensions are

* LIKE operator in AND clause

* free-text triple matching like (?x, ?y, %"whatever"%)

AUTHOR

            

              
              
Alberto Reggiori <areggiori@webweaving.org>
Andy Seaborne <andy_seaborne@hp.com> is the original author of RDQL
Libby Miller <libby.miller@bristol.ac.uk> is the original author of SquishQL