Class: JSON::LD::Writer

Inherits:
RDF::Writer
  • Object
show all
Includes:
Utils
Defined in:
lib/json/ld/writer.rb

Overview

A JSON-LD parser in Ruby.

Note that the natural interface is to write a whole graph at a time. Writing statements or Triples will create a graph to add them to and then serialize the graph.

The writer will add prefix definitions, and use them for creating @context definitions, and minting CURIEs

Select the :expand option to output JSON-LD in expanded form

Examples:

Obtaining a JSON-LD writer class

RDF::Writer.for(:jsonld)         #=> JSON::LD::Writer
RDF::Writer.for("etc/test.json")
RDF::Writer.for(:file_name      => "etc/test.json")
RDF::Writer.for(:file_extension => "json")
RDF::Writer.for(:content_type   => "application/turtle")

Serializing RDF graph into an JSON-LD file

JSON::LD::Writer.open("etc/test.json") do |writer|
  writer << graph
end

Serializing RDF statements into an JSON-LD file

JSON::LD::Writer.open("etc/test.json") do |writer|
  graph.each_statement do |statement|
    writer << statement
  end
end

Serializing RDF statements into an JSON-LD string

JSON::LD::Writer.buffer do |writer|
  graph.each_statement do |statement|
    writer << statement
  end
end

Creating @@context prefix definitions in output

JSON::LD::Writer.buffer(
  :prefixes => {
    nil => "http://example.com/ns#",
    :foaf => "http://xmlns.com/foaf/0.1/"}
) do |writer|
  graph.each_statement do |statement|
    writer << statement
  end
end

See Also:

Instance Attribute Summary collapse

Class Method Summary collapse

Instance Method Summary collapse

Methods included from Utils

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

Constructor Details

#initialize(output = $stdout, options = {}) {|writer| ... } ⇒ Writer

Initializes the RDF-LD writer instance.

Options Hash (options):

  • :encoding (Encoding) — default: Encoding::UTF_8 —

    the encoding to use on the output stream (Ruby 1.9+)

  • :canonicalize (Boolean) — default: false —

    whether to canonicalize literals when serializing

  • :prefixes (Hash) — default: {} —

    the prefix mappings to use (not supported by all writers)

  • :standard_prefixes (Boolean) — default: false —

    Add standard prefixes to @prefixes, if necessary.

  • :context (IO, Array, Hash, String, Context) — default: {} —

    context to use when serializing. Constructed context for native serialization.

  • :unique_bnodes (Boolean) — default: false —

    Use unique bnode identifiers, defaults to using the identifier which the node was originall initialized with (if any).

Yields:

  • (writer) —

    ‘self`

  • (writer)

Yield Parameters:

  • writer (RDF::Writer)
  • writer (RDF::Writer)

Yield Returns:

  • (void) 


95
96
97
98
99
100
101
102
103
104
105
106
107
108
 
# File 'lib/json/ld/writer.rb', line 95

def initialize(output = $stdout, options = {}, &block)
  options[:base_uri] ||= options[:base] if options.has_key?(:base)
  options[:base] ||= options[:base_uri] if options.has_key?(:base_uri)
  super do
    @repo = RDF::Repository.new

    if block_given?
      case block.arity
        when 0 then instance_eval(&block)
        else block.call(self)
      end
    end
  end
end

Instance Attribute Details

#context ⇒ Context (readonly) 



63
64
65
 
# File 'lib/json/ld/writer.rb', line 63

def context
  @context
end

#graph ⇒ RDF::Graph (readonly) 



59
60
61
 
# File 'lib/json/ld/writer.rb', line 59

def graph
  @graph
end

Class Method Details

.to_sym ⇒ Object

Override normal symbol generation



67
68
69
 
# File 'lib/json/ld/writer.rb', line 67

def self.to_sym
  :jsonld
end

Instance Method Details

#write_epilogue ⇒ void

This method returns an undefined value.

Outputs the Serialized JSON-LD representation of all stored statements.

If provided a context or prefixes, we’ll create a context and use it to compact the output. Otherwise, we return un-compacted JSON-LD

See Also:



148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
 
# File 'lib/json/ld/writer.rb', line 148

def write_epilogue
  @debug = @options[:debug]

  debug("writer") { "serialize #{@repo.count} statements, #{@options.inspect}"}
  result = API.fromRdf(@repo, @options)

  # If we were provided a context, or prefixes, use them to compact the output
  context = RDF::Util::File.open_file(@options[:context]) if @options[:context].is_a?(String)
  context ||= @options[:context]
  context ||= if @options[:prefixes] || @options[:language] || @options[:standard_prefixes]
    ctx = Context.new(@options)
    ctx.language = @options[:language] if @options[:language]
    @options[:prefixes].each do |prefix, iri|
      ctx.set_mapping(prefix, iri) if prefix && iri
    end if @options[:prefixes]
    ctx
  end

  # Rename BNodes to uniquify them, if necessary
  if options[:unique_bnodes]
    result = API.flatten(result, context, @options)
  end

  # Perform compaction, if we have a context
  if context
    debug("writer") { "compact result"}
    result = API.compact(result, context,  @options)
  end

  @output.write(result.to_json(JSON_STATE))
end

#write_graph(graph) ⇒ void

This method returns an undefined value.

Write whole graph



115
116
117
118
 
# File 'lib/json/ld/writer.rb', line 115

def write_graph(graph)
  debug {"Add graph #{graph.inspect}"}
  @repo = graph
end

#write_statement(statement) ⇒ void

This method returns an undefined value.

Adds a statement to be serialized



124
125
126
 
# File 'lib/json/ld/writer.rb', line 124

def write_statement(statement)
  @repo.insert(statement)
end

#write_triple(subject, predicate, object) ⇒ void

This method is abstract.

This method returns an undefined value.

Addes a triple to be serialized

Raises:

  • (NotImplementedError) —

    unless implemented in subclass



136
137
138
 
# File 'lib/json/ld/writer.rb', line 136

def write_triple(subject, predicate, object)
  @repo.insert(Statement.new(subject, predicate, object))
end