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Contents
module SPARQL; module Algebra
class Operator
##
# The SPARQL Property Path `alt` (Alternative Property Path) operator.
#
# Let P and Q be property path expressions.
#
# eval(Path(X, alt(P,Q), Y)) = Union(eval(Path(X, P, Y)), eval(Path(X, Q, Y)))
#
# @example
# (alt a b)
#
# @see http://www.w3.org/TR/sparql11-query/#defn_evalPP_alternative
class Alt < Operator::Binary
include Query
NAME = :alt
##
# Equivalent to:
#
# (path x (alt :p :q) y)
# => (union (bgp (x :p y)) (bgp (x :q y)))
#
# @param [RDF::Queryable] queryable
# the graph or repository to query
# @param [Hash{Symbol => Object}] options
# any additional keyword options
# @option options [RDF::Term, RDF::Variable] :subject
# @option options [RDF::Term, RDF::Variable] :object
# @yield [solution]
# each matching solution
# @yieldparam [RDF::Query::Solution] solution
# @yieldreturn [void] ignored
# @see http://www.w3.org/TR/sparql11-query/#sparqlAlgebra
def execute(queryable, options = {}, &block)
subject, object = options[:subject], options[:object]
debug(options) {"Alt #{[subject, operands, object].to_sse}"}
# Solutions where predicate exists
qa = if operand(0).is_a?(RDF::Term)
RDF::Query.new do |q|
q.pattern [subject, operand(0), object]
end
else
operand(0)
end
qb = if operand(1).is_a?(RDF::Term)
RDF::Query.new do |q|
q.pattern [subject, operand(1), object]
end
else
operand(1)
end
query = Union.new(qa, qb)
queryable.query(query, options.merge(depth: options[:depth].to_i + 1), &block)
end
end # Alt
end # Operator
end; end # SPARQL::Algebra
Version data entries
10 entries across 10 versions & 1 rubygems