Module: JSON::LD::FromTriples
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
#blank_node?, #list?, #subject?, #subject_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) defaultGraph = {:subjects => {}, :listMap => {}, :name => ''} graphs = {'' => defaultGraph} value = nil ec = EvaluationContext.new # Create a map for subject to object representation # For each triple in input input.each do |statement| debug("statement") { statement.to_nquads.chomp} subject = ec.(statement.subject).to_s name = statement.context ? ec.(statement.context).to_s : '' # Create a graph entry as needed graph = graphs[name] ||= {:subjects => {}, :listMap => {}, :name => name} case statement.predicate when RDF.first # If property is rdf:first, # create a new entry in _listMap_ for _name_ and _subject_ and an array value # containing the object representation and continue to the next statement. listMap = graph[:listMap] entry = listMap[subject] ||= {} object_rep = ec.(nil, statement.object) entry[:first] = object_rep debug("rdf:first") { "save entry for #{subject.inspect} #{entry.inspect}"} next when RDF.rest # If property is rdf:rest, # and object is a blank node, # create a new entry in _restMap_ for _name_ and _subject_ and a value being the # result of IRI expansion on the object and continue to the next statement. next unless statement.object.is_a?(RDF::Node) listMap = graph[:listMap] entry = listMap[subject] ||= {} object_rep = ec.(statement.object).to_s entry[:rest] = object_rep debug("rdf:rest") { "save entry for #{subject.inspect} #{entry.inspect}"} next end # Add entry to default graph for name unless it is empty defaultGraph[:subjects][name] ||= {'@id' => name} unless name.empty? # Get value from graph subjects for subject, initializing it to a new subject declaration for subject if it does not exist debug("@id") { "new subject: #{subject}"} unless graph[:subjects].has_key?(subject) value = graph[:subjects][subject] ||= {'@id' => subject} # If property is http://www.w3.org/1999/02/22-rdf-syntax-ns#type # and the notType option is not true if statement.predicate == RDF.type && !@options[:notType] object = ec.(statement.object).to_s debug("@type") { object.inspect} # append the string representation of object to the array value for the key @type, creating # an entry if necessary (value['@type'] ||= []) << object elsif statement.object == RDF.nil # Otherwise, if object is http://www.w3.org/1999/02/22-rdf-syntax-ns#nil, let # key be the string representation of predicate. Set the value # for key to an empty @list representation {"@list": []} key = ec.(statement.predicate).to_s (value[key] ||= []) << {"@list" => []} else # Otherwise, let key be the string representation of predicate and let object representation # be object represented in expanded form as described in Value Expansion. key = ec.(statement.predicate).to_s object = ec.(key, statement.object, :native => false) if blank_node?(object) # if object is an Unnamed Node, set as the head element in the listMap # entry for object listMap = graph[:listMap] entry = listMap[object['@id']] ||= {} entry[:head] = object debug("bnode") { "save entry #{entry.inspect}"} end debug("key/value") { "key: #{key}, :value #{object.inspect}"} # append the object object representation to the array value for key, creating # an entry if necessary (value[key] ||= []) << object end end # Build lists for each graph graphs.each do |name, graph| graph[:listMap].each do |subject, entry| debug("listMap(#{name}, #{subject})") { entry.inspect} if entry.has_key?(:head) && entry.has_key?(:first) debug("@list") { "List head for #{subject.inspect} in #{name.inspect}: #{entry.inspect}"} value = entry[:head] value.delete('@id') list = value['@list'] = [entry[:first]].compact while rest = entry.fetch(:rest, nil) entry = graph[:listMap][rest] debug(" => ") { "add #{entry.inspect}"} raise JSON::LD::ProcessingError, "list entry missing rdf:first" unless entry.has_key?(:first) list << entry[:first] end end end end # Build graphs in @id order debug("graphs") {graphs.to_json(JSON_STATE)} array = defaultGraph[:subjects].keys.sort.map do |subject| entry = defaultGraph[:subjects][subject] debug("=> default") {entry.to_json(JSON_STATE)} # If subject is a named graph, add serialized subject defintions if graphs.has_key?(subject) && !subject.empty? entry['@graph'] = graphs[subject][:subjects].keys.sort.map do |s| debug("=> #{s.inspect}") graphs[subject][:subjects][s] end end debug("default graph") {entry.inspect} entry end # Return array as the graph representation. debug("fromRdf") {array.to_json(JSON_STATE)} array end |