RDF::Trine::Pattern - Class for basic graph patterns
This document describes RDF::Trine::Pattern version 1.019
- "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.
Please report any bugs or feature requests to through the GitHub
web interface at <https://github.com/kasei/perlrdf/issues>.
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>.
Gregory Todd Williams
"<gwilliams@cpan.org>"
Kjetil Kjernsmo
"<kjetilk@cpan.org>"
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.