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Contents
module SPARQL; module Algebra
class Operator
##
# The SPARQL `isTRIPLE` operator.
#
# Returns true if term is an RDF-star triple. Returns false otherwise.
#
# [121] BuiltInCall ::= ... | 'isTreiple' '(' Expression ')'
#
# @example SPARQL Grammar
# PREFIX : <http://example.com/ns#>
# SELECT * {
# ?t :source :g
# FILTER(isTriple(?t))
# FILTER(SUBJECT(?t) = :s)
# FILTER(PREDICATE(?t) = :p)
# FILTER(OBJECT(?t) = :o)
# }
#
# @example SSE
# (prefix
# ((: <http://example.com/ns#>))
# (filter
# (exprlist
# (isTRIPLE ?t)
# (= (subject ?t) :s)
# (= (predicate ?t) :p)
# (= (object ?t) :o))
# (bgp (triple ?t :source :g))) )
#
# @see https://w3c.github.io/rdf-star/rdf-star-cg-spec.html#istriple
class IsTriple < Operator::Unary
include Evaluatable
NAME = :isTRIPLE
##
# Returns `true` if the operand is an `RDF::Statement`, `false` otherwise.
#
# @param [RDF::Term] term
# an RDF term
# @return [RDF::Literal::Boolean] `true` or `false`
# @raise [TypeError] if the operand is not an RDF term
def apply(term, **options)
case term
when RDF::Statement then RDF::Literal::TRUE
when RDF::Term then RDF::Literal::FALSE
else raise TypeError, "expected an RDF::Term, but got #{term.inspect}"
end
end
##
#
# Returns a partial SPARQL grammar for this operator.
#
# @return [String]
def to_sparql(**options)
"isTRIPLE(" + operands.first.to_sparql(**options) + ")"
end
end # IsTriple
end # Operator
end; end # SPARQL::Algebra
Version data entries
8 entries across 8 versions & 1 rubygems