NAME

RDF::Query::Algebra::GroupGraphPattern - Algebra class for GroupGraphPattern patterns

VERSION

This document describes RDF::Query::Algebra::GroupGraphPattern version 2.200, released 6 August 2009.

METHODS

new ( @graph_patterns )

Returns a new GroupGraphPattern structure.

construct_args

Returns a list of arguments that, passed to this class' constructor, will produce a clone of this algebra pattern.

patterns

Returns a list of the graph patterns in this GGP.

add_pattern

Appends a new child pattern to the GGP.

sse

Returns the SSE string for this alegbra expression.

as_sparql

Returns the SPARQL string for this alegbra expression.

type

Returns the type of this algebra expression.

referenced_variables

Returns a list of the variable names used in this algebra expression.

definite_variables

Returns a list of the variable names that will be bound after evaluating this algebra expression.

fixup ( $query, $bridge, $base, \%namespaces )

Returns a new pattern that is ready for execution using the given bridge. This method replaces generic node objects with bridge-native objects.

execute ( $query, $bridge, \%bound, $context, %args )

join_bnode_streams ( $streamA, $streamB, $query, $bridge )

A modified inner-loop join that relies on there being bnode identity hints in the data returned by $streamB->extra_result_data. These hints are combined with locally computed identity values for the items from $streamA and the streams are merged using a natural join where equality is computed either on direct node equality or on any intersection of the identity hints.

The identity hints and locally computed identity values are computed using Functional and InverseFunctional property values using N3 syntax. For example, a blank node '(r1)' might have identity hints using foaf:mbox_sha1sum such as:

$extra_result_data = {
    'bnode-map' => [ {
        '(r1)' => ['!<http://xmlns.com/foaf/0.1/mbox_sha1sum>"26fb6400147dcccfda59717ff861db9cb97ac5ec"']
    } ]
};

AUTHOR

Gregory Todd Williams <gwilliams@cpan.org>