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Contents
module SPARQL; module Algebra
class Operator
##
# The SPARQL GraphPattern `ask` operator.
#
# @example
# (prefix ((: <http://example/>))
# (ask
# (bgp (triple :x :p ?x))))
#
# @see http://www.w3.org/TR/rdf-sparql-query/#ask
class Ask < Operator::Unary
include Query
NAME = [:ask]
##
# Executes this query on the given `queryable` graph or repository.
# Returns true if any solutions are found, false otherwise.
#
# @param [RDF::Queryable] queryable
# the graph or repository to query
# @param [Hash{Symbol => Object}] options
# any additional keyword options
# @yield [RDF::Literal::Boolean]
# @yieldparam [RDF::Query::Solution] solution
# @yieldreturn [void] ignored
# @return [RDF::Literal::Boolean]\
# @see http://www.w3.org/TR/rdf-sparql-query/#sparqlAlgebra
def execute(queryable, options = {})
debug(options) {"Ask #{operands.first}"}
res = boolean(!queryable.query(operands.last, options.merge(:depth => options[:depth].to_i + 1)).empty?)
yield res if block_given?
res
end
##
# Returns an optimized version of this query.
#
# Return optimized query
#
# @return [Union, RDF::Query] `self`
def optimize
operands = operands.map(&:optimize)
end
# Query results in a boolean result (e.g., ASK)
# @return [Boolean]
def query_yields_boolean?
true
end
end # Ask
end # Operator
end; end # SPARQL::Algebra
Version data entries
5 entries across 5 versions & 1 rubygems