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Contents
module LD::Patch::Algebra
##
# 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.
#
# @example
# (reverse :p)
#
# 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.
class Reverse < SPARQL::Algebra::Operator::Unary
include SPARQL::Algebra::Query
include SPARQL::Algebra::Evaluatable
NAME = :reverse
##
# Executes this upate on the given `writable` graph or repository.
#
# @param [RDF::Queryable] queryable
# the graph or repository to write
# @param [Hash{Symbol => Object}] options
# any additional options
# @option options [Array<RDF::Term>] starting terms
# @return [RDF::Query::Solutions] solutions with `:term` mapping
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
end
end
Version data entries
4 entries across 4 versions & 1 rubygems