NAME

       RDF::Trine::Pattern - Class for basic graph patterns

VERSION

       This document describes RDF::Trine::Pattern version 1.014

METHODS

       "new ( @triples )"
           Returns a new BasicGraphPattern structure.

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

       "triples"
           Returns a list of triples belonging to this BGP.

       "type"
       "sse"
           Returns the SSE string for 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.

       "clone"
       "bind_variables ( \%bound )"
           Returns a new pattern with variables named in %bound replaced by their corresponding
           bound values.

       "subsumes ( $statement )"
           Returns true if the pattern will subsume the $statement when matched against a triple
           store.

       "merge_patterns ( @patterns )"
           Given an array of patterns, this will merge them into one.

       "sort_for_join_variables"
           Returns a new pattern object with the subpatterns of the referrant sorted based on
           heuristics that ensure firstly that patterns can be joined on the same variable and
           secondly on the usual selectivity (i.e. how quickly the engine can drill down to the
           answer) of triple patterns. Calls "subgroup", "sort_triples" and "merge_patterns" in
           that order.

       "subgroup"
           Splits the pattern object up in an array of pattern objects where the same triple
           patterns occur. It will group on common variables, so that triple patterns can be
           joined together is in a group together. It will also group triples that have no
           connection to other triples in a group. It will then order the groups, first by number
           triples with common variables, then by number of literals, then by the total number of
           terms that are not variables.

       "sort_triples"
           Will sort the triple patterns based on heuristics that looks at how many variables the
           patterns have, and where they occur, see REFERENCES for details. Returns a new sorted
           pattern object.

BUGS

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

REFERENCES

       The heuristics to order triple patterns in this module is strongly influenced by The ICS-
       FORTH Heuristics-based SPARQL Planner (HSP)
       <http://www.ics.forth.gr/isl/index_main.php?l=e&c=645>.

AUTHOR

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

       Kjetil Kjernsmo "<kjetilk@cpan.org>"

COPYRIGHT

       Copyright (c) 2006-2012 Gregory Todd Williams. This program is free software; you can
       redistribute it and/or modify it under the same terms as Perl itself.