Class: LD::Patch::Algebra::Reverse

Inherits:
SPARQL::Algebra::Operator::Unary
  • Object
show all
Includes:
SPARQL::Algebra::Evaluatable, SPARQL::Algebra::Query
Defined in:
lib/ld/patch/algebra/reverse.rb

Overview

The LD Patch reverse operator

Finds all the terms which are the subject of triples where the operand is the predicate and input terms are objects.

Queries queryable for subjects where input terms are objects and the predicate is :p, by executing the reverse operand using input terms to get a set of output terms.

Examples:

(reverse :p)

Constant Summary collapse

NAME = 
:reverse

Instance Method Summary collapse

Instance Method Details

#execute(queryable, options = {}) ⇒ RDF::Query::Solutions

Executes this upate on the given writable graph or repository.

Parameters:

  • queryable (RDF::Queryable) —

    the graph or repository to write

  • options (Hash{Symbol => Object}) (defaults to: {}) —

    any additional options

Options Hash (options):

  • starting (Array<RDF::Term>) —

    terms

Returns:

  • (RDF::Query::Solutions) —

    solutions with :term mapping



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# File 'lib/ld/patch/algebra/reverse.rb', line 27

def execute(queryable, options = {})
  debug(options) {"Reverse"}
  op = operand(0)
  terms = Array(options.fetch(:terms))

  results = terms.map do |object|
    queryable.query({object: object, predicate: op}).map(&:subject)
  end.flatten

  RDF::Query::Solutions.new(results.map {|t| RDF::Query::Solution.new(path: t)})
end