Class: RDF::N3::Algebra::Log::Implies

Inherits:
SPARQL::Algebra::Operator::Binary
  • Object
show all
Includes:
Builtin, SPARQL::Algebra::Query, SPARQL::Algebra::Update
Defined in:
lib/rdf/n3/algebra/log/implies.rb

Overview

Logical implication.

This is the relation between the antecedent (subject) and conclusion (object) of a rule. The application of a rule to a knowledge-base is as follows. For every substitution which, applied to the antecedent, gives a formula which is a subset of the knowledge-base, then the result of applying that same substitution to the conclusion may be added to the knowledge-base.

related: See log:conclusion.

Constant Summary collapse

NAME = 
:logImplies
URI = 
RDF::N3::Log.implies

Instance Attribute Summary

Attributes included from Enumerable

#existentials, #universals

Instance Method Summary collapse

Methods included from Builtin

#evaluate, #hash, #input_operand, #rank, #to_uri

Instance Method Details

#clear_solutions ⇒ Object

Clear out any cached solutions. This principaly is for log:conclusions



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# File 'lib/rdf/n3/algebra/log/implies.rb', line 63

def clear_solutions
  super
  @solutions = nil
end

#each(solutions: RDF::Query::Solutions()) {|statement| ... } ⇒ Object

Yields statements from the object based on solutions determined from the subject. Each solution formed by querying ‘queryable` from the subject is used to create a graph, which must be a subgraph of `queryable`. If so, that solution is used to generate triples from the object formula which are yielded.

Yields:

  • (statement) —

    each matching statement

Yield Parameters:

Yield Returns:

  • (void) —

    ignored



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# File 'lib/rdf/n3/algebra/log/implies.rb', line 75

def each(solutions: RDF::Query::Solutions(), &block)
  # Merge solutions in with those for the evaluation of this implication
  # Clear out solutions so they don't get remembered erroneously.
  solutions, @solutions = Array(@solutions), nil
  log_depth do
    super(solutions: RDF::Query::Solutions(RDF::Query::Solution.new), &block)

    solutions.each do |solution|
      log_info("(logImplies each) solution") {SXP::Generator.string solution.to_sxp_bin}
      object = operand(1).evaluate(solution.bindings, formulae: formulae)
      log_info("(logImplies each) object") {SXP::Generator.string object.to_sxp_bin}

      # Yield inferred statements
      log_depth do
        object.each(solutions: RDF::Query::Solutions(solution)) do |statement|
          log_debug(("(logImplies each) infer\s")) {statement.to_sxp}
          block.call(RDF::Statement.from(statement.to_quad, inferred: true))
        end
      end
    end
  end
end

#execute(queryable, solutions:, **options) ⇒ RDF::Solutions

Returns solutions from subject. Solutions are created by evaluating subject against ‘queryable`.

Solutions are kept within this instance, and used for conclusions. Note that the evaluated solutions do not affect that of the invoking formula, as the solution spaces are disjoint.

Parameters:

  • queryable (RDF::Queryable) —

    the graph or repository to query

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

    any additional keyword options

Options Hash (**options):

  • solutions (RDF::Query::Solutions) —

    optional initial solutions for chained queries

Returns:

  • (RDF::Solutions) —

    distinct solutions



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# File 'lib/rdf/n3/algebra/log/implies.rb', line 28

def execute(queryable, solutions:, **options)
  @queryable = queryable
  @solutions = RDF::Query::Solutions(solutions.map do |solution|
    log_debug(NAME, "solution") {SXP::Generator.string(solution.to_sxp_bin)}
    subject = operand(0).evaluate(solution.bindings, formulae: formulae)
    object = operand(1).evaluate(solution.bindings, formulae: formulae)
    log_info(NAME,  "subject") {SXP::Generator.string(subject.to_sxp_bin)}
    log_info(NAME, "object") {SXP::Generator.string(object.to_sxp_bin)}

    # Nothing to do if variables aren't resolved.
    next unless subject && object

    solns = log_depth {subject.execute(queryable, solutions: RDF::Query::Solutions(solution), **options)}

    # Execute object as well (typically used for log:outputString)
    solns.each do |soln|
      log_depth {object.execute(queryable, solutions: RDF::Query::Solutions(soln), **options)}
    end

    # filter solutions where not all variables in antecedant are bound.
    vars = subject.universal_vars
    solns = RDF::Query::Solutions(solns.to_a.select do |soln|
      vars.all? {|v| soln.bound?(v)}
    end)
    solns
  end.flatten.compact.uniq)
  log_info(NAME) {SXP::Generator.string(@solutions.to_sxp_bin)}

  # Return original solutions, without bindings
  solutions
end

#graph_name ⇒ RDF::Resource

Graph name associated with this operation, using the name of the parent

Returns:

  • (RDF::Resource) 


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# File 'lib/rdf/n3/algebra/log/implies.rb', line 100

def graph_name; parent.graph_name; end