NAME

Attean::SimpleQueryEvaluator - Simple query evaluator

VERSION

This document describes Attean::SimpleQueryEvaluator version 0.033

SYNOPSIS

  use v5.14;
  use Attean;
  my $algebra = Attean->get_parser('SPARQL')->parse('SELECT * WHERE { ... }');
  my $active_graph = Attean::IRI->new('http://example.org/');
  my $e = Attean::SimpleQueryEvaluator->new( model => $model );
  my $iter = $e->evaluate( $algebra, $active_graph );

DESCRIPTION

The Attean::SimpleQueryEvaluator class implements a simple query evaluator that, given an Attean::API::Algebra and a Attean::API::Model object, evaluates the query represented by the algebra using data from the model, and returns a query result.

ATTRIBUTES

"model"

The Attean::API::Model object used for query evaluation.

"default_graph"

The Attean::API::IRI object representing the default graph in the "model". The default graph will be excluded from enumeration of graph names for query features such as "GRAPH ?g {}".

"request_signer"

If set, used to modify HTTP::Request objects used in evaluating SERVICE calls before the request is made. This may be used to, for example, add cryptographic signature headers to the request. The modification is performed by calling "$request_signer->sign( $request )".

METHODS

"evaluate( $algebra, $active_graph )"

Returns an Attean::API::Iterator object with results produced by evaluating the query $algebra against the evaluator's "model", using the supplied $active_graph.

"evaluate_pattern( $pattern, $active_graph, \@new_vars, \%blanks )"

Returns an Attean::API::Iterator object with results produced by evaluating the triple- or quad-pattern $pattern against the evaluator's "model", using the supplied $active_graph.

If the "ground_blanks" option is false, replaces blank nodes in the pattern with fresh variables before evaluation, and populates %blanks with pairs ($variable_name => $variable_node). Each new variable is also appended to @new_vars as it is created.

BUGS

Please report any bugs or feature requests to through the GitHub web interface at <https://github.com/kasei/attean/issues>.

SEE ALSO

AUTHOR

Gregory Todd Williams "<gwilliams@cpan.org>"

COPYRIGHT

Copyright (c) 2014--2022 Gregory Todd Williams. This program is free software; you can redistribute it and/or modify it under the same terms as Perl itself.