NAME

RDQL::Parser - A simple top-down LL(1) RDQL parser - see http://www.hpl.hp.com/semweb/rdql-grammar.html

SYNOPSIS

	use RDQL::Parser;
	my $parser = RDQL::Parser->new();
	my $query = <<QUERY;

        SELECT
           ?title, ?link
        FROM
           <http://xmlhack.com/rss10.php>
        WHERE
	   (?item, <rdf:type>, <rss:item>),
	   (?item, <rss::title>, ?title),
	   (?item, <rss::link>, ?link)
        USING
	   rdf for <http://www.w3.org/1999/02/22-rdf-syntax-ns#>,
	   rss for <http://purl.org/rss/1.0/>

        QUERY;

        $parser->parse($query); #parse the query

	# I.e.
	$parser = bless( {
                 'constraints' => [],
                 'resultVars' => [ '?title', '?link' ],
                 'triplePatterns' => [
                                       [ '?item', '<rdf:type>', '<rss:item>' ],
                                       [ '?item', '<rss::title>', '?title' ],
                                       [ '?item', '<rss::link>', '?link' ]
                                     ],
                 'sources' => [ '<file:t/rdql-tests/rdf/rss10.php>' ],
                 'prefixes' => {
                                 'rss' => 'http://purl.org/rss/1.0/',
                                 'rdf' => 'http://www.w3.org/1999/02/22-rdf-syntax-ns#'
                               }
               }, '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 parser - see http://www.hpl.hp.com/semweb/rdql-grammar.html

CONSTRUCTORS

$parser = new RDQL::Parser;

METHODS

parse( PARSER, RDQL_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( {
                'constraints' => [],
                'resultVars' => [
                                  '?title',
                                  '?link'
                                ],
                'triplePatterns' => [
                                      [
                                        '?item',
                                        '<rdf:type>',
                                        '<rss:item>'
                                      ],
                                      [
                                        '?item',
                                        '<rss::title>',
                                        '?title'
                                      ],
                                      [
                                        '?item',
                                        '<rss::link>',
                                        '?link'
                                      ]
                                    ],
                'sources' => [
                               '<file:t/rdql-tests/rdf/rss10.php>'
                             ],
                'prefixes' => {
                                'rss' => 'http://purl.org/rss/1.0/',
                                'rdf' => 'http://www.w3.org/1999/02/22-rdf-syntax-ns#'
                              }
              }, 'RDQL::Parser' );

NOTES

The following 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).

SEE ALSO

DBD::RDFStore(3)

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 URLs 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