Class: SPARQL::Algebra::Operator::Seq

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

Overview

The SPARQL Property Path sequence (SequencePath) operator.

[90] PathSequence ::= PathEltOrInverse ( '/' PathEltOrInverse )*

Examples:

SPARQL Grammar

PREFIX ex:  <http://www.example.org/schema#>
PREFIX in:  <http://www.example.org/instance#>
SELECT * WHERE {  in:a ex:p1/ex:p2 ?x }

SSE

(prefix ((ex: <http://www.example.org/schema#>)
         (in: <http://www.example.org/instance#>))
 (path in:a (seq ex:p1 ex:p2) ?x))

See Also:

Constant Summary collapse

NAME = 
:seq

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

Join solution sets

(path :x (seq :p :q) :y)
=> (join (bgp (:x :p ??1)) (bgp (??1 :q :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/seq.rb', line 41

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

  v = RDF::Query::Variable.new(distinguished: false)
  q1 = if operand(0).is_a?(RDF::Term)
    RDF::Query.new do |q|
      q.pattern [subject, operand(0), v]
    end
  else
    operand(0)
  end
  q2 = if operand(1).is_a?(RDF::Term)
    RDF::Query.new do |q|
      q.pattern [v, operand(1), object]
    end
  else
    operand(1)
  end

  left = queryable.query(q1, **options.merge(object: v, depth: options[:depth].to_i + 1))
  #debug(options) {"(seq)=>(left) #{left.map(&:to_h).to_sse}"}

  right = queryable.query(q2, **options.merge(subject: v, depth: options[:depth].to_i + 1))
  #debug(options) {"(seq)=>(right) #{right.map(&:to_h).to_sse}"}

  @solutions = RDF::Query::Solutions(left.map do |s1|
    right.map do |s2|
      s2.merge(s1) if s2.compatible?(s1)
    end
  end.flatten.compact).map do |solution|
    solution.bindings.delete(v.to_sym)
    solution
  end
  debug(options) {"(seq)=> #{@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/seq.rb', line 85

def to_sparql(**options)
  '(' + operands.to_sparql(delimiter: '/', **options) + ')'
end