Class: SPARQL::Algebra::Operator::PathOpt

Inherits:
Operator::Unary
  • Object
show all
Includes:
Query
Defined in:
lib/sparql/algebra/operator/path_opt.rb

Overview

Examples:

SPARQL Grammar

PREFIX : <http://example/> 
SELECT * WHERE {
  :a (:p/:p)? ?t
}

SSE

(prefix ((: <http://example/>))
 (path :a (path? (seq :p :p)) ?t))

See Also:

Constant Summary collapse

NAME = 
:path?

Instance Attribute Summary

Attributes included from Query

#solutions

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

Instance Method Details

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

Optional path:

(path x (path? :p) y)
=> (union (bgp ((x :p y))) (filter (x = y) (solution x y)))

Parameters:

  • queryable (RDF::Queryable) —

    the graph or repository to query

  • options (Hash{Symbol => Object}) —

    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 'lib/sparql/algebra/operator/path_opt.rb', line 42

def execute(queryable, **options, &block)
  subject, object = options[:subject], options[:object]
  debug(options) {"Path? #{[subject, operands, object].to_sse}"}

  query = PathZero.new(operand)
  solutions = query.execute(queryable, **options.merge(depth: options[:depth].to_i + 1))

  # Solutions where predicate exists
  query = if operand.is_a?(RDF::Term)
    RDF::Query.new do |q|
      q.pattern [subject, operand, object]
    end
  else # path
    operand
  end

  # Recurse into query
  solutions += query.execute(queryable, **options.merge(depth: options[:depth].to_i + 1))
  debug(options) {"(path?)=> #{solutions.to_sxp}"}
  solutions.each(&block) if block_given?
  solutions
end

#to_sparql(**options) ⇒ String

Returns a partial SPARQL grammar for this operator.

Returns:

  • (String) 


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# File 'lib/sparql/algebra/operator/path_opt.rb', line 70

def to_sparql(**options)
  "(#{operands.first.to_sparql(**options)})?"
end