Class: JSON::LD::Writer

Inherits:
RDF::Writer
  • Object
show all
Includes:
StreamingWriter, Utils, RDF::Util::Logger
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:

Author:

Class Attribute Summary collapse

Instance Attribute Summary collapse

Class Method Summary collapse

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?

Methods included from StreamingWriter

#stream_epilogue, #stream_prologue, #stream_statement

Constructor Details

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

Initializes the JSON-LD writer instance.

Parameters:

  • output (IO, File) (defaults to: $stdout)

    the output stream

  • options (Hash{Symbol => Object})

    any additional options

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.

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

    frame to use when serializing.

  • :unique_bnodes (Boolean) — default: false

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

  • serializer (Proc) — default: JSON::LD::API.serializer

    A Serializer method used for generating the JSON serialization of the result.

  • :stream (Boolean) — default: false

    Do not attempt to optimize graph presentation, suitable for streaming large graphs.

Yields:

  • (writer)

    self

  • (writer)

Yield Parameters:

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

Yield Returns:

  • (void)


254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
# File 'lib/json/ld/writer.rb', line 254

def initialize(output = $stdout, **options, &block)
  options[:base_uri] ||= options[:base] if options.key?(:base)
  options[:base] ||= options[:base_uri] if options.key?(:base_uri)
  @serializer = options.fetch(:serializer, JSON::LD::API.method(:serializer))
  super do
    @repo = RDF::Repository.new

    if block
      case block.arity
      when 0 then instance_eval(&block)
      else yield(self)
      end
    end
  end
end

Class Attribute Details

.black_listObject (readonly)

Returns the value of attribute black_list.



193
194
195
# File 'lib/json/ld/writer.rb', line 193

def black_list
  @black_list
end

.default_contextString

Returns default context used for compacted profile without an explicit context URL

Returns:

  • (String)


214
215
216
# File 'lib/json/ld/writer.rb', line 214

def default_context
  @default_context || JSON::LD::DEFAULT_CONTEXT
end

.white_listObject (readonly)

Returns the value of attribute white_list.



193
194
195
# File 'lib/json/ld/writer.rb', line 193

def white_list
  @white_list
end

Instance Attribute Details

#contextContext (readonly)

Returns context used to load and administer contexts.

Returns:

  • (Context)

    context used to load and administer contexts



71
72
73
# File 'lib/json/ld/writer.rb', line 71

def context
  @context
end

#graphRDF::Graph (readonly)

Returns Graph of statements serialized.

Returns:

  • (RDF::Graph)

    Graph of statements serialized



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

def graph
  @graph
end

Class Method Details

.accept?(accept_params) {|accept_params| ... } ⇒ Boolean

Use parameters from accept-params to determine if the parameters are acceptable to invoke this writer. The accept_params will subsequently be provided to the writer instance.

Parameters:

  • accept_params (Hash{Symbol => String})

Yields:

  • (accept_params)

    if a block is given, returns the result of evaluating that block

Yield Parameters:

  • accept_params (Hash{Symbol => String})

Returns:

  • (Boolean)

See Also:



203
204
205
206
207
208
209
# File 'lib/json/ld/writer.rb', line 203

def accept?(accept_params)
  if block_given?
    yield(accept_params)
  else
    true
  end
end

.optionsObject

JSON-LD Writer options



76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
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
179
180
181
182
183
184
185
186
187
188
189
190
# File 'lib/json/ld/writer.rb', line 76

def self.options
  super + [
    RDF::CLI::Option.new(
      symbol: :compactArrays,
      datatype: TrueClass,
      default: true,
      control: :checkbox,
      on: ["--[no-]compact-arrays"],
      description: "Replaces arrays with just one element with that element during compaction. Default is `true` use --no-compact-arrays to disable."
    ) { |arg| arg },
    RDF::CLI::Option.new(
      symbol: :compactToRelative,
      datatype: TrueClass,
      default: true,
      control: :checkbox,
      on: ["--[no-]compact-to-relative"],
      description: "Creates document relative IRIs when compacting, if `true`, otherwise leaves expanded. Default is `true` use --no-compact-to-relative to disable."
    ) { |arg| arg },
    RDF::CLI::Option.new(
      symbol: :context,
      datatype: RDF::URI,
      control: :url2,
      on: ["--context CONTEXT"],
      description: "Context to use when compacting."
    ) { |arg| RDF::URI(arg).absolute? ? RDF::URI(arg) : StringIO.new(File.read(arg)) },
    RDF::CLI::Option.new(
      symbol: :embed,
      datatype: %w[@always @once @never],
      default: '@once',
      control: :select,
      on: ["--embed EMBED"],
      description: "How to embed matched objects (@once)."
    ) { |arg| RDF::URI(arg) },
    RDF::CLI::Option.new(
      symbol: :explicit,
      datatype: TrueClass,
      control: :checkbox,
      on: ["--[no-]explicit"],
      description: "Only include explicitly declared properties in output (false)"
    ) { |arg| arg },
    RDF::CLI::Option.new(
      symbol: :frame,
      datatype: RDF::URI,
      control: :url2,
      use: :required,
      on: ["--frame FRAME"],
      description: "Frame to use when serializing."
    ) { |arg| RDF::URI(arg).absolute? ? RDF::URI(arg) : StringIO.new(File.read(arg)) },
    RDF::CLI::Option.new(
      symbol: :lowercaseLanguage,
      datatype: TrueClass,
      control: :checkbox,
      on: ["--[no-]lowercase-language"],
      description: "By default, language tags are left as is. To normalize to lowercase, set this option to `true`."
    ),
    RDF::CLI::Option.new(
      symbol: :omitDefault,
      datatype: TrueClass,
      control: :checkbox,
      on: ["--[no-]omitDefault"],
      description: "Omit missing properties from output (false)"
    ) { |arg| arg },
    RDF::CLI::Option.new(
      symbol: :ordered,
      datatype: TrueClass,
      control: :checkbox,
      on: ["--[no-]ordered"],
      description: "Order object member processing lexographically."
    ) { |arg| arg },
    RDF::CLI::Option.new(
      symbol: :processingMode,
      datatype: %w[json-ld-1.0 json-ld-1.1],
      control: :radio,
      on: ["--processingMode MODE", %w[json-ld-1.0 json-ld-1.1]],
      description: "Set Processing Mode (json-ld-1.0 or json-ld-1.1)"
    ),
    RDF::CLI::Option.new(
      symbol: :rdfDirection,
      datatype: %w[i18n-datatype compound-literal],
      default: 'null',
      control: :select,
      on: ["--rdf-direction DIR", %w[i18n-datatype compound-literal]],
      description: "How to serialize literal direction (i18n-datatype compound-literal)"
    ) { |arg| arg },
    RDF::CLI::Option.new(
      symbol: :requireAll,
      datatype: TrueClass,
      default: true,
      control: :checkbox,
      on: ["--[no-]require-all"],
      description: "Require all properties to match (true). Default is `true` use --no-require-all to disable."
    ) { |arg| arg },
    RDF::CLI::Option.new(
      symbol: :stream,
      datatype: TrueClass,
      control: :checkbox,
      on: ["--[no-]stream"],
      description: "Do not attempt to optimize graph presentation, suitable for streaming large graphs."
    ) { |arg| arg },
    RDF::CLI::Option.new(
      symbol: :useNativeTypes,
      datatype: TrueClass,
      control: :checkbox,
      on: ["--[no-]use-native-types"],
      description: "Use native JSON values in value objects."
    ) { |arg| arg },
    RDF::CLI::Option.new(
      symbol: :useRdfType,
      datatype: TrueClass,
      control: :checkbox,
      on: ["--[no-]use-rdf-type"],
      description: "Treat `rdf:type` like a normal property instead of using `@type`."
    ) { |arg| arg }
  ]
end

Instance Method Details

#write_epilogue

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:



313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
# File 'lib/json/ld/writer.rb', line 313

def write_epilogue
  if @options[:stream]
    stream_epilogue
  else

    # log_debug("writer") { "serialize #{@repo.count} statements, #{@options.inspect}"}
    result = API.fromRdf(@repo, **@options.merge(serializer: nil))

    # Some options may be indicated from accept parameters
    profile = @options.fetch(:accept_params, {}).fetch(:profile, "").split
    links = LinkHeader.parse(@options[:link])
    @options[:context] ||= begin
      links.find_link(['rel', JSON_LD_NS + "context"]).href
    rescue StandardError
      nil
    end
    @options[:context] ||= Writer.default_context if profile.include?(JSON_LD_NS + "compacted")
    @options[:frame] ||= begin
      links.find_link(['rel', JSON_LD_NS + "frame"]).href
    rescue StandardError
      nil
    end

    # If we were provided a context, or prefixes, use them to compact the output
    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
      ctx
    end

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

    if (frame = @options[:frame])
      # Perform framing, if given a frame
      # log_debug("writer") { "frame result"}
      result = API.frame(result, frame, **@options.merge(serializer: nil))
    elsif context
      # Perform compaction, if we have a context
      # log_debug("writer") { "compact result"}
      result = API.compact(result, context, **@options.merge(serializer: nil))
    end

    @output.write(@serializer.call(result, **@options))
  end

  super
end

#write_prologue

This method returns an undefined value.

Necessary for streaming



300
301
302
303
# File 'lib/json/ld/writer.rb', line 300

def write_prologue
  stream_prologue if @options[:stream]
  super
end

#write_quad(subject, predicate, object, graph_name)

This method returns an undefined value.

Outputs the N-Quads representation of a statement.

Parameters:

  • subject (RDF::Resource)
  • predicate (RDF::URI)
  • object (RDF::Term)


288
289
290
291
292
293
294
295
# File 'lib/json/ld/writer.rb', line 288

def write_quad(subject, predicate, object, graph_name)
  statement = RDF::Statement.new(subject, predicate, object, graph_name: graph_name)
  if @options[:stream]
    stream_statement(statement)
  else
    @repo.insert(statement)
  end
end

#write_triple(subject, predicate, object)

This method is abstract.

This method returns an undefined value.

Addes a triple to be serialized

Parameters:

  • subject (RDF::Resource)
  • predicate (RDF::URI)
  • object (RDF::Value)


277
278
279
# File 'lib/json/ld/writer.rb', line 277

def write_triple(subject, predicate, object)
  write_quad(subject, predicate, object, nil)
end