Module: JSON::LD::FromRDF
Instance Method Summary collapse
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#from_statements(input) ⇒ Array<Hash>
Generate a JSON-LD array representation from an array of ‘RDF::Statement`.
Methods included from Utils
#as_resource, #blank_node?, #index?, #list?, #node?, #node_reference?, #value?
Instance Method Details
#from_statements(input) ⇒ Array<Hash>
Generate a JSON-LD array representation from an array of ‘RDF::Statement`. Representation is in expanded form
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# File 'lib/json/ld/from_rdf.rb', line 13 def from_statements(input) default_graph = {} graph_map = {'@default' => default_graph} value = nil ec = Context.new # Create a map for node to object representation # For each triple in input input.each do |statement| debug("statement") { statement.to_nquads.chomp} name = statement.context ? ec.(statement.context).to_s : '@default' # Create a graph entry as needed node_map = graph_map[name] ||= {} default_graph[name] ||= {'@id' => name} unless name == '@default' subject = ec.(statement.subject).to_s node = node_map[subject] ||= {'@id' => subject} # If object is an IRI or blank node identifier, does not equal rdf:nil, and node map does not have an object member, create one and initialize its value to a new JSON object consisting of a single member @id whose value is set to object. node_map[statement.object.to_s] ||= {'@id' => statement.object.to_s} unless statement.object.literal? || statement.object == RDF.nil # If predicate equals rdf:type, and object is an IRI or blank node identifier, append object to the value of the @type member of node. If no such member exists, create one and initialize it to an array whose only item is object. Finally, continue to the next RDF triple. if statement.predicate == RDF.type && statement.object.resource? merge_value(node, '@type', statement.object.to_s) next end # If object equals rdf:nil and predicate does not equal rdf:rest, set value to a new JSON object consisting of a single member @list whose value is set to an empty array. value = if statement.object == RDF.nil && statement.predicate != RDF.rest {'@list' => []} else ec.(nil, statement.object, @options) end merge_value(node, statement.predicate.to_s, value) # If object is a blank node identifier and predicate equals neither rdf:first nor rdf:rest, it might represent the head of a RDF list: if statement.object.node? && ![RDF.first, RDF.rest].include?(statement.predicate) merge_value(node_map[statement.object.to_s], :usages, value) end end # For each name and graph object in graph map: graph_map.each do |name, graph_object| subjects = graph_object.keys subjects.each do |subj| next unless graph_object.has_key?(subj) node = graph_object[subj] next unless node[:usages].is_a?(Array) && node[:usages].length == 1 debug("list head") {node.to_json(JSON_STATE)} value = node[:usages].first list, list_nodes, subject = [], [], subj while subject != RDF.nil.to_s && list if node.nil? || !blank_node?(node) || node.keys.any? {|k| !["@id", :usages, RDF.first.to_s, RDF.rest.to_s].include?(k)} || !(f = node[RDF.first.to_s]).is_a?(Array) || f.length != 1 || !(r = node[RDF.rest.to_s]).is_a?(Array) || r.length != 1 || !node_reference?(r.first) || list_nodes.include?(subject) debug("list") {"not valid list element: #{node.to_json(JSON_STATE)}"} list = nil else list << f.first list_nodes << node['@id'] subject = r.first['@id'] node = graph_object[subject] debug("list") {"rest: #{node.to_json(JSON_STATE)}"} list = nil if list_nodes.include?(subject) end end next if list.nil? value.delete('@id') value['@list'] = list list_nodes.each {|s| graph_object.delete(s)} end end result = [] debug("graph_map") {graph_map.to_json(JSON_STATE)} default_graph.keys.sort.each do |subject| node = default_graph[subject] if graph_map.has_key?(subject) node['@graph'] = [] graph_map[subject].keys.sort.each do |s| n = graph_map[subject][s] n.delete(:usages) node['@graph'] << n end end node.delete(:usages) result << node end debug("fromRDF") {result.to_json(JSON_STATE)} result end |