Module: JSON::LD::Triples

Includes:
Utils
Included in:
API
Defined in:
lib/json/ld/to_rdf.rb

Instance Method Summary collapse

Methods included from Utils

#blank_node?, #list?, #node?, #node_reference?, #value?

Instance Method Details

#add_quad(path, subject, predicate, object, name) {|:statement| ... } ⇒ Object

add a statement, object can be literal or URI or bnode

Parameters:

  • path (String)
  • subject (RDF::Resource) —

    the subject of the statement

  • predicate (RDF::URI) —

    the predicate of the statement

  • object (RDF::Term) —

    the object of the statement

  • name (RDF::Resource) —

    the named graph context of the statement

Yields:

  • :statement

Yield Parameters:

  • :statement (RDF::Statement) 


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# File 'lib/json/ld/to_rdf.rb', line 172

def add_quad(path, subject, predicate, object, name)
  predicate = RDF.type if predicate == '@type'
  object = context.expand_iri(object.to_s, :quiet => true) if object.literal? && predicate == RDF.type
  statement = RDF::Statement.new(subject, predicate, object, :context => name)
  debug(path) {"statement: #{statement.to_nquads}"}
  yield statement
end

#node ⇒ Object

Create a new named node using the sequence



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# File 'lib/json/ld/to_rdf.rb', line 156

def node
  n = RDF::Node.new(@node_seq)
  @node_seq = @node_seq.succ
  n
end

#parse_list(path, list, property, name) {|:statement| ... } ⇒ RDF::Resource

Parse a List

Parameters:

  • path (String) —

    location within JSON hash

  • list (Array) —

    The Array to serialize as a list

  • property (RDF::URI) —

    Inherited property

  • name (RDF::Resource) —

    Inherited named graph context

Yields:

  • :statement

Yield Parameters:

  • :statement (RDF::Statement)

Returns:

  • (RDF::Resource) —

    BNode or nil for head of list



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# File 'lib/json/ld/to_rdf.rb', line 132

def parse_list(path, list, property, name, &block)
  debug(path) {"list: #{list.inspect}, p=#{property.inspect}, n=#{name.inspect}"}

  last = list.pop
  result = first_bnode = last ? node : RDF.nil

  depth do
    list.each do |list_item|
      # Traverse the value
      statements("#{path}", list_item, first_bnode, RDF.first, name, &block)
      rest_bnode = node
      add_quad("#{path}", first_bnode, RDF.rest, rest_bnode, name, &block)
      first_bnode = rest_bnode
    end
    if last
      statements("#{path}", last, first_bnode, RDF.first, name, &block)
      add_quad("#{path}", first_bnode, RDF.rest, RDF.nil, name, &block)
    end
  end
  result
end

#statements(path, element, subject, property, name) {|:statement| ... } ⇒ RDF::Resource

Returns defined by this element.

Parameters:

  • path (String) —

    location within JSON hash

  • element (Hash, Array, String) —

    The current JSON element being processed

  • subject (RDF::Node) —

    Inherited subject

  • property (RDF::URI) —

    Inherited property

  • name (RDF::Node) —

    Inherited inherited graph name

Yields:

  • :statement

Yield Parameters:

  • :statement (RDF::Statement)

Returns:

  • (RDF::Resource) —

    defined by this element



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# File 'lib/json/ld/to_rdf.rb', line 22

def statements(path, element, subject, property, name, &block)
  debug(path) {"statements: e=#{element.inspect}, s=#{subject.inspect}, p=#{property.inspect}, n=#{name.inspect}"}
  @node_seq = "t0" unless subject || property

  traverse_result = depth do
    case element
    when Hash
      # Other shortcuts to allow use of this method for terminal associative arrays
      object = if element.has_key?('@value')
        # 1.2) If the JSON object has a @value key, set the active object to a literal value as follows ...
        literal_opts = {}
        literal_opts[:datatype] = RDF::URI(element['@type']) if element['@type']
        literal_opts[:language] = element['@language'].to_sym if element['@language']
        RDF::Literal.new(element['@value'], literal_opts)
      elsif element.has_key?('@list')
        # 1.3 (Lists)
        parse_list("#{path}[#{'@list'}]", element['@list'], property, name, &block)
      end

      if object
        # 1.4
        add_quad(path, subject, property, object, name, &block) if subject && property
        return object
      end
    
      active_subject = if element.fetch('@id', nil).is_a?(String)
        # 1.5 Subject
        # 1.5.1 Set active object (subject)
        context.expand_iri(element['@id'], :quiet => true)
      else
        # 1.6) Generate a blank node identifier and set it as the active subject.
        node
      end

      # 1.7) For each key in the JSON object that has not already been processed,
      # perform the following steps:
      element.keys.sort.each do |key|
        value = element[key]
        active_property = case key
        when '@type'
          # If the key is @type, set the active property to rdf:type.
          RDF.type
        when '@graph'
          # Otherwise, if property is @graph, process value algorithm recursively, using active subject
          # as graph name and null values for active subject and active property and then continue to
          # next property
          statements("#{path}[#{key}]", value, nil, nil, active_subject, &block)
          next
        when /^@/
          # Otherwise, if property is a keyword, skip this step.
          next
        else
          # 1.7.1) If a key that is not @id, @graph, or @type, set the active property by
          # performing Property Processing on the key.
          context.expand_iri(key, :quiet => true)
        end

        debug("statements[Step 1.7.4]")
        statements("#{path}[#{key}]", value, active_subject, active_property, name, &block)
      end
    
      # 1.8) The active_subject is returned
      active_subject
    when Array
      # 2) If a regular array is detected ...
      debug("statements[Step 2]")
      element.each_with_index do |v, i|
        statements("#{path}[#{i}]", v, subject, property, name, &block)
      end
      nil # No real value returned from an array
    when String
      object = RDF::Literal.new(element)
      debug(path) {"statements[Step 3]: plain: #{object.inspect}"}
      object
    when Float
      object = RDF::Literal::Double.new(element)
      debug(path) {"statements[Step 4]: native: #{object.inspect}"}
      object
    when Fixnum
      object = RDF::Literal.new(element)
      debug(path) {"statements[Step 5]: native: #{object.inspect}"}
      object
    when TrueClass, FalseClass
      object = RDF::Literal::Boolean.new(element)
      debug(path) {"statements[Step 6]: native: #{object.inspect}"}
      object
    else
      raise RDF::ReaderError, "Traverse to unknown element: #{element.inspect} of type #{element.class}"
    end
  end

  # Yield and return traverse_result
  add_quad(path, subject, property, traverse_result, name, &block) if subject && property && traverse_result
  traverse_result
end