#!/usr/bin/perl
use strict;
use warnings;
use RDF::Query;
unless (@ARGV) {
        print STDERR <<"END";
USAGE: $0 query.rq http://path/to/data.rdf
Reads in a SPARQL query from query.rq, and loads RDF data from the supplied URL.
The SPARQL query is executed against a triplestore containing the loaded RDF,
and query results are printed to standard output.
END
        exit;
}
# get the query file from the arguments array
my $query_file  = shift(@ARGV);
#open the query file and read in the query
my $sparql      = do { local($/) = undef; open(my $fh, '<:utf8', $query_file); <$fh> };
# construct the query object
my $query       = RDF::Query->new( $sparql );
unless ($query) {
        # the query couldn't be constructed. print out the reason why.
        warn RDF::Query->error;
        exit;
}
# create a temporary triplestore (in memory), and wrap it into a model
my $store       = RDF::Trine::Store::DBI->temporary_store();
my $model       = RDF::Trine::Model->new( $store );
# load the RDF data from the url into the model.
# the parse_url_into_model method will attempt to guess the appropriate format for parsing.
my $url = shift(@ARGV);
RDF::Trine::Parser->parse_url_into_model( $url, $model );
# execute the query against data contained in the model
my $iter        = $query->execute( $model );
# print the results as a string to standard output
print $iter->as_string;
### or, if you want to iterator over each result row:
# while (my $s = $iter->next) {
#       print $s . "\n";
# }