Module: JSON::LD::Flatten

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

Instance Method Summary collapse

Methods included from Utils

#add_value, #as_array, #as_resource, #blank_node?, #compare_values, #graph?, #has_value?, #index?, #list?, #node?, #node_or_ref?, #node_reference?, #property?, #simple_graph?, #value?

Instance Method Details

#create_annotations(node_map) ⇒ Hash{String => Hash}

Create annotations

Updates a node map from which annotations have been folded into embedded triples to re-extract the annotations.

Map entries where the key is of the form of a canonicalized JSON object are used to find keys with the ‘@id` and property components. If found, the original map entry is removed and entries added to an `@annotation` property of the associated value.

  • Keys which are of the form of a canonicalized JSON object are examined in inverse order of length.

  • Deserialize the key into a map, and re-serialize the value of ‘@id`.

  • If the map contains an entry with that value (after re-canonicalizing, as appropriate), and the associated antry has a item which matches the non-‘@id` item from the map, the node is used to create an `@annotation` entry within that value.

Parameters:

  • node_map (Hash{String => Hash})

Returns:

  • (Hash{String => Hash}) 


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# File 'lib/json/ld/flatten.rb', line 216

def create_annotations(node_map)
  node_map.keys
    .select { |k| k.start_with?('{') }
    .sort_by(&:length)
    .reverse_each do |key|
    annotation = node_map[key]
    # Deserialize key, and re-serialize the `@id` value.
    emb = annotation['@id'].dup
    id = emb.delete('@id')
    property, value = emb.to_a.first

    # If id is a map, set it to the result of canonicalizing that value, otherwise to itself.
    id = id.to_json_c14n if id.is_a?(Hash)

    next unless node_map.key?(id)

    # If node map has an entry for id and that entry contains the same property and value from entry:
    node = node_map[id]

    next unless node.key?(property)

    node[property].each do |emb_value|
      next unless emb_value == value.first

      node_map.delete(key)
      annotation.delete('@id')
      add_value(emb_value, '@annotation', annotation, property_is_array: true) unless
        annotation.empty?
    end
  end
end

#create_node_map(element, graph_map, active_graph: '@default', active_subject: nil, active_property: nil, reverse: false, list: nil) ⇒ Object

This algorithm creates a JSON object node map holding an indexed representation of the graphs and nodes represented in the passed expanded document. All nodes that are not uniquely identified by an IRI get assigned a (new) blank node identifier. The resulting node map will have a member for every graph in the document whose value is another object with a member for every node represented in the document. The default graph is stored under the @default member, all other graphs are stored under their graph name.

For RDF-star/JSON-LD-star:

* Values of `@id` can be an object (embedded node); when these are used as keys in a Node Map, they are serialized as canonical JSON, and de-serialized when flattening.
* The presence of `@annotation` implies an embedded node and the annotation object is removed from the node/value object in which it appears.

Parameters:

  • element (Array, Hash) —

    Expanded JSON-LD input

  • graph_map (Hash) —

    A map of graph name to subjects

  • active_graph (String) (defaults to: '@default') —

    The name of the currently active graph that the processor should use when processing.

  • active_subject (String) (defaults to: nil) —

    (nil) Node identifier

  • active_property (String) (defaults to: nil) —

    (nil) Property within current node

  • reverse (Boolean) (defaults to: false) —

    (false) Processing a reverse relationship

  • list (Array) (defaults to: nil) —

    (nil) Used when property value is a list



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# File 'lib/json/ld/flatten.rb', line 30

def create_node_map(element, graph_map,
                    active_graph: '@default',
                    active_subject: nil,
                    active_property: nil,
                    reverse: false,
                    list: nil)
  if element.is_a?(Array)
    # If element is an array, process each entry in element recursively by passing item for element, node map, active graph, active subject, active property, and list.
    element.map do |o|
      create_node_map(o, graph_map,
        active_graph: active_graph,
        active_subject: active_subject,
        active_property: active_property,
        reverse: false,
        list: list)
    end
  elsif !element.is_a?(Hash)
    raise "Expected hash or array to create_node_map, got #{element.inspect}"
  else
    graph = (graph_map[active_graph] ||= {})
    subject_node = !reverse && graph[active_subject.is_a?(Hash) ? active_subject.to_json_c14n : active_subject]

    # Transform BNode types
    if element.key?('@type')
      element['@type'] = Array(element['@type']).map { |t| blank_node?(t) ? namer.get_name(t) : t }
    end

    if value?(element)
      element['@type'] = element['@type'].first if element['@type']

      # For rdfstar, if value contains an `@annotation` member ...
      # note: active_subject will not be nil, and may be an object itself.
      if element.key?('@annotation')
        # rdfstar being true is implicit, as it is checked in expansion
        as = if node_reference?(active_subject)
          active_subject['@id']
        else
          active_subject
        end
        star_subject = {
          "@id" => as,
          active_property => [element]
        }

        # Note that annotation is an array, make the reified subject the id of each member of that array.
        annotation = element.delete('@annotation').map do |a|
          a.merge('@id' => star_subject)
        end

        # Invoke recursively using annotation.
        create_node_map(annotation, graph_map,
          active_graph: active_graph)
      end

      if list.nil?
        add_value(subject_node, active_property, element, property_is_array: true, allow_duplicate: false)
      else
        list['@list'] << element
      end
    elsif list?(element)
      result = { '@list' => [] }
      create_node_map(element['@list'], graph_map,
        active_graph: active_graph,
        active_subject: active_subject,
        active_property: active_property,
        list: result)
      if list.nil?
        add_value(subject_node, active_property, result, property_is_array: true)
      else
        list['@list'] << result
      end
    else
      # Element is a node object
      ser_id = id = element.delete('@id')
      if id.is_a?(Hash)
        # Index graph using serialized id
        ser_id = id.to_json_c14n
      elsif id.nil?
        ser_id = id = namer.get_name
      end

      node = graph[ser_id] ||= { '@id' => id }

      if reverse
        # NOTE: active_subject is a Hash
        # We're processing a reverse-property relationship.
        add_value(node, active_property, active_subject, property_is_array: true, allow_duplicate: false)
      elsif active_property
        reference = { '@id' => id }
        if list.nil?
          add_value(subject_node, active_property, reference, property_is_array: true, allow_duplicate: false)
        else
          list['@list'] << reference
        end
      end

      # For rdfstar, if node contains an `@annotation` member ...
      # note: active_subject will not be nil, and may be an object itself.
      # XXX: what if we're reversing an annotation?
      if element.key?('@annotation')
        # rdfstar being true is implicit, as it is checked in expansion
        as = if node_reference?(active_subject)
          active_subject['@id']
        else
          active_subject
        end
        star_subject = if reverse
          { "@id" => node['@id'], active_property => [{ '@id' => as }] }
        else
          { "@id" => as, active_property => [{ '@id' => node['@id'] }] }
        end

        # Note that annotation is an array, make the reified subject the id of each member of that array.
        annotation = element.delete('@annotation').map do |a|
          a.merge('@id' => star_subject)
        end

        # Invoke recursively using annotation.
        create_node_map(annotation, graph_map,
          active_graph: active_graph,
          active_subject: star_subject)
      end

      if element.key?('@type')
        add_value(node, '@type', element.delete('@type'), property_is_array: true, allow_duplicate: false)
      end

      if element['@index']
        if node.key?('@index') && node['@index'] != element['@index']
          raise JsonLdError::ConflictingIndexes,
            "Element already has index #{node['@index']} dfferent from #{element['@index']}"
        end
        node['@index'] = element.delete('@index')
      end

      if element['@reverse']
        referenced_node = { '@id' => id }
        reverse_map = element.delete('@reverse')
        reverse_map.each do |property, values|
          values.each do |value|
            create_node_map(value, graph_map,
              active_graph: active_graph,
              active_subject: referenced_node,
              active_property: property,
              reverse: true)
          end
        end
      end

      if element['@graph']
        create_node_map(element.delete('@graph'), graph_map,
          active_graph: id)
      end

      if element['@included']
        create_node_map(element.delete('@included'), graph_map,
          active_graph: active_graph)
      end

      element.each_key do |property|
        value = element[property]

        property = namer.get_name(property) if blank_node?(property)
        node[property] ||= []
        create_node_map(value, graph_map,
          active_graph: active_graph,
          active_subject: id,
          active_property: property)
      end
    end
  end
end

#rename_bnodes(node) ⇒ Hash

Rename blank nodes recursively within an embedded object

Parameters:

  • node (Object)

Returns:

  • (Hash) 


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# File 'lib/json/ld/flatten.rb', line 253

def rename_bnodes(node)
  case node
  when Array
    node.map { |n| rename_bnodes(n) }
  when Hash
    node.each_with_object({}) do |(k, v), memo|
      v = namer.get_name(v) if k == '@id' && v.is_a?(String) && blank_node?(v)
      memo[k] = rename_bnodes(v)
    end
  else
    node
  end
end