Class: SPARQL::Algebra::Operator::Alt

Inherits:
Binary show all
Includes:
Query
Defined in:
vendor/bundler/ruby/2.4.0/bundler/gems/sparql-e0a915196943/lib/sparql/algebra/operator/alt.rb

Overview

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)))

Constant Summary

NAME =
:alt

Constants inherited from Binary

Binary::ARITY

Constants inherited from SPARQL::Algebra::Operator

ARITY, IsURI, URI

Instance Attribute Summary

Attributes included from Query

#solutions

Attributes inherited from SPARQL::Algebra::Operator

#operands

Instance Method Summary collapse

Methods included from Query

#each_solution, #empty?, #failed?, #graph_name=, #matched?, #query_yields_boolean?, #query_yields_solutions?, #query_yields_statements?, #unshift, #variables

Methods inherited from Binary

#initialize

Methods inherited from SPARQL::Algebra::Operator

#aggregate?, arity, base_uri, #base_uri, base_uri=, #boolean, #constant?, #each_descendant, #eql?, #evaluatable?, evaluate, #executable?, #first_ancestor, for, #initialize, #inspect, #ndvars, #node?, #operand, #optimize, #parent, #parent=, prefixes, #prefixes, prefixes=, #rewrite, #to_binary, #to_sxp, #to_sxp_bin, #validate!, #variable?, #vars

Methods included from Expression

cast, #constant?, #evaluate, extension, extensions, for, #invalid?, new, #node?, open, #optimize, parse, register_extension, #to_sxp_bin, #valid?, #validate!, #variable?

Constructor Details

This class inherits a constructor from SPARQL::Algebra::Operator::Binary

Instance Method Details

#execute(queryable, options = {}) {|solution| ... } ⇒ Object

Equivalent to:

(path x (alt :p :q) y) => (union (bgp (x :p y)) (bgp (x :q y)))

Parameters:

  • queryable (RDF::Queryable)

    the graph or repository to query

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

    any additional keyword options

Options Hash (options):

Yields:

  • (solution)

    each matching solution

Yield Parameters:

Yield Returns:

  • (void)

    ignored

See Also:



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# File 'vendor/bundler/ruby/2.4.0/bundler/gems/sparql-e0a915196943/lib/sparql/algebra/operator/alt.rb', line 36

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