Class: RDF::Statement

Inherits:
Object
  • Object
show all
Includes:
Value
Defined in:
lib/rdf/model/statement.rb

Overview

An RDF statement.

Examples:

Creating an RDF statement

s = RDF::URI.new("https://rubygems.org/gems/rdf")
p = RDF::Vocab::DC.creator
o = RDF::URI.new("http://ar.to/#self")
RDF::Statement(s, p, o)

Creating an RDF statement with a graph_name

uri = RDF::URI("http://example/")
RDF::Statement(s, p, o, graph_name: uri)

Creating an RDF statement from a Hash

RDF::Statement({
  subject:   RDF::URI.new("https://rubygems.org/gems/rdf"),
  predicate: RDF::Vocab::DC.creator,
  object:    RDF::URI.new("http://ar.to/#self"),
})

Creating an RDF statement with interned nodes

RDF::Statement(:s, p, :o)

Creating an RDF statement with a string

RDF::Statement(s, p, "o")

Direct Known Subclasses

Query::Pattern

Instance Attribute Summary collapse

Class Method Summary collapse

Instance Method Summary collapse

Methods included from Value

#anonymous?, #constant?, #graph?, #inspect, #inspect!, #iri?, #list?, #literal?, #resource?, #start_with?, #term?, #to_nquads, #to_ntriples, #to_rdf, #to_term, #type_error, #uri?, #validate!

Constructor Details

#initialize(**options) ⇒ RDF::Statement #initialize(subject, predicate, object, **options) ⇒ RDF::Statement

Returns a new instance of Statement.

Overloads:

  • #initialize(**options) ⇒ RDF::Statement

    Parameters:

    Options Hash (**options):

    • :subject (RDF::Term) — default: nil —

      A symbol is converted to an interned Node.

    • :predicate (RDF::URI) — default: nil
    • :object (RDF::Resource) — default: nil —

      if not a Resource, it is coerced to Literal or Node depending on if it is a symbol or something other than a Term.

    • :graph_name (RDF::Term) — default: nil —

      Note, in RDF 1.1, a graph name MUST be an Resource.

    • :inferred (Boolean) —

      used as a marker to record that this statement was inferred based on semantic relationships (T-Box).

  • #initialize(subject, predicate, object, **options) ⇒ RDF::Statement

    Parameters:

    • A symbol is converted to an interned Node.

    • if not a Resource, it is coerced to Literal or Node depending on if it is a symbol or something other than a Term.

    Options Hash (**options):

    • :graph_name (RDF::Term) — default: nil —

      Note, in RDF 1.1, a graph name MUST be an Resource.

    • :inferred (Boolean) —

      used as a marker to record that this statement was inferred based on semantic relationships (T-Box).



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# File 'lib/rdf/model/statement.rb', line 87

def initialize(subject = nil, predicate = nil, object = nil, options = {})
  if subject.is_a?(Hash)
    @options   = Hash[subject] # faster subject.dup
    @subject   = @options.delete(:subject)
    @predicate = @options.delete(:predicate)
    @object    = @options.delete(:object)
  else
    @options   = !options.empty? ? Hash[options] : {}
    @subject   = subject
    @predicate = predicate
    @object    = object
  end
  @id          = @options.delete(:id) if @options.has_key?(:id)
  @graph_name  = @options.delete(:graph_name)
  initialize!
end

Instance Attribute Details

#graph_name ⇒ RDF::Resource

Returns:



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# File 'lib/rdf/model/statement.rb', line 49

def graph_name
  @graph_name
end

#id ⇒ Object

Returns:



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# File 'lib/rdf/model/statement.rb', line 46

def id
  @id
end

#object ⇒ RDF::Term

Returns:



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# File 'lib/rdf/model/statement.rb', line 58

def object
  @object
end

#options ⇒ Hash{Symbol => Object}

Returns:



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# File 'lib/rdf/model/statement.rb', line 61

def options
  @options
end

#predicate ⇒ RDF::URI

Returns:



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# File 'lib/rdf/model/statement.rb', line 55

def predicate
  @predicate
end

#subject ⇒ RDF::Resource

Returns:



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# File 'lib/rdf/model/statement.rb', line 52

def subject
  @subject
end

Class Method Details

.from(statement, graph_name: nil, **options) ⇒ Object

Since:

  • 0.2.2



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# File 'lib/rdf/model/statement.rb', line 34

def self.from(statement, graph_name: nil, **options)
  case statement
    when Array, Query::Pattern
      graph_name ||= statement[3] == false ? nil : statement[3]
      self.new(statement[0], statement[1], statement[2], graph_name: graph_name, **options)
    when Statement then statement
    when Hash      then self.new(options.merge(statement))
    else raise ArgumentError, "expected RDF::Statement, Hash, or Array, but got #{statement.inspect}"
  end
end

Instance Method Details

#==(other) ⇒ Boolean

Checks statement equality as a triple.

Parameters:

Returns:

See Also:



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# File 'lib/rdf/model/statement.rb', line 265

def ==(other)
  to_a == Array(other) &&
    !(other.is_a?(RDF::Value) && other.list?)
end

#===(other) ⇒ Boolean

Checks statement equality with patterns.

Uses #eql? to compare each of #subject, #predicate, #object, and #graph_name to those of other. Any statement part which is not present in self is ignored.

Examples:

statement = RDF::Statement.new(RDF::URI('s'), RDF::URI('p'), RDF::URI('o'))
pattern   = RDF::Statement.new(RDF::URI('s'), RDF::URI('p'), RDF::Query::Variable.new)

# true
statement === statement
pattern   === statement
RDF::Statement.new(nil, nil, nil) === statement

# false
statement === pattern
statement === RDF::Statement.new(nil, nil, nil)

Parameters:

Returns:

See Also:



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# File 'lib/rdf/model/statement.rb', line 297

def ===(other)
  return false if has_object?    && !object.eql?(other.object)
  return false if has_predicate? && !predicate.eql?(other.predicate)
  return false if has_subject?   && !subject.eql?(other.subject)
  return false if has_graph?     && !graph_name.eql?(other.graph_name)
  return true
end

#[](index) ⇒ RDF::Term

Parameters:

Returns:



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# File 'lib/rdf/model/statement.rb', line 308

def [](index)
  case index
    when 0 then self.subject
    when 1 then self.predicate
    when 2 then self.object
    when 3 then self.graph_name
    else nil
  end
end

#[]=(index, value) ⇒ RDF::Term

Parameters:

Returns:



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# File 'lib/rdf/model/statement.rb', line 322

def []=(index, value)
  case index
    when 0 then self.subject   = value
    when 1 then self.predicate = value
    when 2 then self.object    = value
    when 3 then self.graph_name   = value
    else nil
  end
end

#asserted? ⇒ Boolean

Returns:



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# File 'lib/rdf/model/statement.rb', line 166

def asserted?
  !quoted?
end

#canonicalize ⇒ RDF::Statement

Returns a version of the statement with each position in canonical form

Returns:

  • self or nil if statement cannot be canonicalized

Since:

  • 1.0.8



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# File 'lib/rdf/model/statement.rb', line 366

def canonicalize
  self.dup.canonicalize!
rescue ArgumentError
  nil
end

#canonicalize! ⇒ RDF::Statement

Canonicalizes each unfrozen term in the statement

Returns:

  • self

Raises:

  • if any element cannot be canonicalized.

Since:

  • 1.0.8



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# File 'lib/rdf/model/statement.rb', line 351

def canonicalize!
  self.subject.canonicalize!    if has_subject? && !self.subject.frozen?
  self.predicate.canonicalize!  if has_predicate? && !self.predicate.frozen?
  self.object.canonicalize!     if has_object? && !self.object.frozen?
  self.graph_name.canonicalize! if has_graph? && !self.graph_name.frozen?
  self.validate!
  @hash = nil
  self
end

#complete? ⇒ Boolean

Determines if the statement is complete, vs. invalid. A complete statement is one in which none of subject, predicate, or object, are nil.

Returns:

Since:

  • 3.0



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# File 'lib/rdf/model/statement.rb', line 196

def complete?
  !incomplete?
end

#eql?(other) ⇒ Boolean

Checks statement equality as a quad.

Parameters:

Returns:

See Also:



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# File 'lib/rdf/model/statement.rb', line 245

def eql?(other)
  other.is_a?(Statement) && self == other && (self.graph_name || false) == (other.graph_name || false)
end

#has_graph? ⇒ Boolean Also known as: has_name?

Returns:



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# File 'lib/rdf/model/statement.rb', line 202

def has_graph?
  !!graph_name
end

#has_object? ⇒ Boolean

Returns:



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# File 'lib/rdf/model/statement.rb', line 221

def has_object?
  !!object
end

#has_predicate? ⇒ Boolean

Returns:



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# File 'lib/rdf/model/statement.rb', line 215

def has_predicate?
  !!predicate
end

#has_subject? ⇒ Boolean

Returns:



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# File 'lib/rdf/model/statement.rb', line 209

def has_subject?
  !!subject
end

#hash ⇒ Object

Generates a Integer hash value as a quad.



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# File 'lib/rdf/model/statement.rb', line 251

def hash
  @hash ||= to_quad.hash
end

#incomplete? ⇒ Boolean

Determines if the statement is incomplete, vs. invalid. An incomplete statement is one in which any of subject, predicate, or object, are nil.

Returns:

Since:

  • 3.0



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# File 'lib/rdf/model/statement.rb', line 187

def incomplete?
  to_triple.any?(&:nil?)
end

#inferred? ⇒ Boolean

Returns:



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# File 'lib/rdf/model/statement.rb', line 178

def inferred?
  !!@options[:inferred]
end

#initialize! ⇒ Object 



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# File 'lib/rdf/model/statement.rb', line 106

def initialize!
  @graph_name   = Node.intern(@graph_name)   if @graph_name.is_a?(Symbol)
  @subject   = if @subject.is_a?(Value)
    @subject.to_term
  elsif @subject.is_a?(Symbol)
    Node.intern(@subject)
  elsif @subject.nil?
    nil
  else
    raise ArgumentError, "expected subject to be nil or a term, was #{@subject.inspect}"
  end
  @predicate = Node.intern(@predicate) if @predicate.is_a?(Symbol)
  @object    = if @object.is_a?(Value)
    @object.to_term
  elsif @object.is_a?(Symbol)
    Node.intern(@object)
  elsif @object.nil?
    nil
  else
    Literal.new(@object)
  end
end

#invalid? ⇒ Boolean

Returns:



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# File 'lib/rdf/model/statement.rb', line 151

def invalid?
  !valid?
end

#node? ⇒ Boolean Also known as: has_blank_nodes?

Returns true if any resource of this statement is a blank node.

Returns:

Since:

  • 2.0



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# File 'lib/rdf/model/statement.rb', line 230

def node?
  to_quad.compact.any?(&:node?)
end

#quoted? ⇒ Boolean

Returns:



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# File 'lib/rdf/model/statement.rb', line 172

def quoted?
  false
end

#reified(subject: nil, id: nil, graph_name: nil) ⇒ RDF::Graph

Returns a graph containing this statement in reified form.

Parameters:

  • (defaults to: nil)

    (nil) Subject of reification.

  • (defaults to: nil)

    (nil) Node identifier, when subject is anonymous

  • (defaults to: nil)

    (nil) Note, in RDF 1.1, a graph name MUST be an Resource.

Returns:

See Also:



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# File 'lib/rdf/model/statement.rb', line 404

def reified(subject: nil, id: nil, graph_name: nil)
  RDF::Graph.new(graph_name: graph_name) do |graph|
    subject = subject || RDF::Node.new(id)
    graph << [subject, RDF.type,      RDF[:Statement]]
    graph << [subject, RDF.subject,   self.subject]
    graph << [subject, RDF.predicate, self.predicate]
    graph << [subject, RDF.object,    self.object]
  end
end

#statement? ⇒ Boolean

Returns true to indicate that this value is a statement.

Returns:



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# File 'lib/rdf/model/statement.rb', line 133

def statement?
  true
end

#to_h(subject_key = :subject, predicate_key = :predicate, object_key = :object, graph_key = :graph_name) ⇒ Hash{Symbol => RDF::Term}

Returns the terms of this statement as a Hash.

Parameters:

  • (defaults to: :subject)
  • (defaults to: :predicate)
  • (defaults to: :object)

Returns:



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# File 'lib/rdf/model/statement.rb', line 379

def to_h(subject_key = :subject, predicate_key = :predicate, object_key = :object, graph_key = :graph_name)
  {subject_key => subject, predicate_key => predicate, object_key => object, graph_key => graph_name}
end

#to_quad ⇒ Array(RDF::Term)

Returns:



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# File 'lib/rdf/model/statement.rb', line 334

def to_quad
  [subject, predicate, object, graph_name]
end

#to_s ⇒ String

Returns a string representation of this statement.

Returns:



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# File 'lib/rdf/model/statement.rb', line 387

def to_s
  (graph_name ? to_quad : to_triple).map do |term|
    term.respond_to?(:to_base) ? term.to_base : term.inspect
  end.join(" ") + " ."
end

#to_triple ⇒ Array(RDF::Term) Also known as: to_a

Returns:



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# File 'lib/rdf/model/statement.rb', line 340

def to_triple
  [subject, predicate, object]
end

#valid? ⇒ Boolean

Returns:



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# File 'lib/rdf/model/statement.rb', line 157

def valid?
  has_subject?    && subject.resource? && subject.valid? &&
  has_predicate?  && predicate.uri? && predicate.valid? &&
  has_object?     && object.term? && object.valid? &&
  (has_graph?      ? (graph_name.resource? && graph_name.valid?) : true)
end

#variable? ⇒ Boolean

Returns true if any element of the statement is not a URI, Node or Literal.

Returns:



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# File 'lib/rdf/model/statement.rb', line 142

def variable?
  !(has_subject?    && subject.resource? &&
    has_predicate?  && predicate.resource? &&
    has_object?     && (object.resource? || object.literal?) &&
    (has_graph?     ? graph_name.resource? : true))
end