Class: RDF::Turtle::Writer

Inherits:
Writer show all
Includes:
StreamingWriter, Util::Logger
Defined in:
vendor/bundler/ruby/3.3.0/bundler/gems/rdf-turtle-6506e92ccd8e/lib/rdf/turtle/writer.rb

Overview

A Turtle serialiser

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 @prefix definitions, and minting QNames

Examples:

Obtaining a Turtle writer class

RDF::Writer.for(:ttl)         #=> RDF::Turtle::Writer
RDF::Writer.for("etc/test.ttl")
RDF::Writer.for(file_name:       "etc/test.ttl")
RDF::Writer.for(file_extension:  "ttl")
RDF::Writer.for(content_type:    "text/turtle")

Serializing RDF graph into an Turtle file

RDF::Turtle::Writer.open("etc/test.ttl") do |writer|
  writer << graph
end

Serializing RDF statements into an Turtle file

RDF::Turtle::Writer.open("etc/test.ttl") do |writer|
  graph.each_statement do |statement|
    writer << statement
  end
end

Serializing RDF statements into an Turtle string

RDF::Turtle::Writer.buffer do |writer|
  graph.each_statement do |statement|
    writer << statement
  end
end

Serializing RDF statements to a string in streaming mode

RDF::Turtle::Writer.buffer(stream:  true) do |writer|
  graph.each_statement do |statement|
    writer << statement
  end
end

Creating @base and @prefix definitions in output

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

Author:

Direct Known Subclasses

RDF::TriG::Writer

Constant Summary

Constants included from Util::Logger

Util::Logger::IOWrapper

Instance Attribute Summary collapse

Attributes inherited from Writer

#options

Class Method Summary collapse

Instance Method Summary collapse

Methods included from Util::Logger

#log_debug, #log_depth, #log_error, #log_fatal, #log_info, #log_recover, #log_recovering?, #log_statistics, #log_warn, #logger

Methods included from StreamingWriter

#stream_epilogue, #stream_prologue, #stream_statement

Methods inherited from Writer

accept?, #base_uri, buffer, #canonicalize?, dump, each, #encoding, #escaped, #flush, for, format, #format_list, #format_quotedTriple, #format_term, #node_id, open, #prefix, #prefixes, #prefixes=, #puts, to_sym, #to_sym, #uri_for, #validate?, #write_comment, #write_statement, #write_triples

Methods included from Util::Aliasing::LateBound

#alias_method

Methods included from Writable

#<<, #insert, #insert_graph, #insert_reader, #insert_statement, #insert_statements, #writable?

Methods included from Util::Coercions

#coerce_statements

Constructor Details

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

Initializes the Turtle 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

  • :canonicalize (Boolean) — default: false —

    whether to canonicalize literals when serializing

  • :prefixes (Hash) — default: Hash.new —

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

  • :base_uri (#to_s) — default: nil —

    the base URI to use when constructing relative URIs

  • :max_depth (Integer) — default: 3 —

    Maximum depth for recursively defining resources, defaults to 3

  • :standard_prefixes (Boolean) — default: false —

    Add standard prefixes to @prefixes, if necessary.

  • :stream (Boolean) — default: false —

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

  • :default_namespace (String) — default: nil —

    URI to use as default namespace, same as prefixes[nil]

  • :unique_bnodes (Boolean) — default: false —

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

  • :literal_shorthand (Boolean) — default: true —

    Attempt to use Literal shorthands for numbers and boolean values

Yields:

  • (writer) —

    self

  • (writer)

Yield Parameters:

Yield Returns:

  • (void) 


126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
 
# File 'vendor/bundler/ruby/3.3.0/bundler/gems/rdf-turtle-6506e92ccd8e/lib/rdf/turtle/writer.rb', line 126

def initialize(output = $stdout, **options, &block)
  @graph = RDF::Graph.new
  @uri_to_pname = {}
  @uri_to_prefix = {}
  options = {literal_shorthand: true}.merge(options)
  super do
    reset
    if block_given?
      case block.arity
        when 0 then instance_eval(&block)
        else block.call(self)
      end
    end
  end
end

Instance Attribute Details

#graph ⇒ Graph

Returns Graph of statements serialized.

Returns:

  • (Graph) —

    Graph of statements serialized



64
65
66
 
# File 'vendor/bundler/ruby/3.3.0/bundler/gems/rdf-turtle-6506e92ccd8e/lib/rdf/turtle/writer.rb', line 64

def graph
  @graph
end

Class Method Details

.options ⇒ Object

Writer options

See Also:



69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
 
# File 'vendor/bundler/ruby/3.3.0/bundler/gems/rdf-turtle-6506e92ccd8e/lib/rdf/turtle/writer.rb', line 69

def self.options
  super + [
    RDF::CLI::Option.new(
      symbol: :max_depth,
      datatype: Integer,
      on: ["--max-depth DEPTH"],
      description: "Maximum depth for recursively defining resources, defaults to 3.") {true},
    RDF::CLI::Option.new(
      symbol: :stream,
      datatype: TrueClass,
      on: ["--stream"],
      description: "Do not attempt to optimize graph presentation, suitable for streaming large graphs.") {true},
    RDF::CLI::Option.new(
      symbol: :default_namespace,
      datatype: RDF::URI,
      on: ["--default-namespace URI", :REQUIRED],
      description: "URI to use as default namespace, same as prefixes.") {|arg| RDF::URI(arg)},
    RDF::CLI::Option.new(
      symbol: :literal_shorthand,
      datatype: FalseClass,
      on: ["--no-literal-shorthand"],
      description: "Do not attempt to use Literal shorthands fo numbers and boolean values.") {false},
  ]
end

Instance Method Details

#blankNodePropertyList(resource, position) ⇒ Object (protected)

Represent resource as a blankNodePropertyList



582
583
584
585
586
587
588
589
590
591
 
# File 'vendor/bundler/ruby/3.3.0/bundler/gems/rdf-turtle-6506e92ccd8e/lib/rdf/turtle/writer.rb', line 582

def blankNodePropertyList(resource, position)
  return false unless blankNodePropertyList?(resource, position)

  log_debug("blankNodePropertyList") {resource.to_ntriples}
  subject_done(resource)
  @output.write(position == :subject ? "\n#{indent} [" : '[')
  num_props = log_depth {predicateObjectList(resource, true)}
  @output.write((num_props > 1 ? "\n#{indent(2)}" : "") + (position == :object ? ']' : '] .'))
  true
end

#blankNodePropertyList?(resource, position) ⇒ Boolean (protected)

Can subject be represented as a blankNodePropertyList?

Returns:

  • (Boolean) 


572
573
574
575
576
577
578
579
 
# File 'vendor/bundler/ruby/3.3.0/bundler/gems/rdf-turtle-6506e92ccd8e/lib/rdf/turtle/writer.rb', line 572

def blankNodePropertyList?(resource, position)
  !resource.statement? && resource.node? &&
    !collection?(resource) &&
    !reifiedTriple?(resource, position) &&
    !in_triple_term?(resource) &&
    (!is_done?(resource) || position == :subject) &&
    ref_count(resource) == (position == :object ? 1 : 0)
end

#bump_reference(resource) ⇒ Integer (protected)

Increase the reference count of this resource

Parameters:

Returns:

  • (Integer) —

    resulting reference count



522
523
524
 
# File 'vendor/bundler/ruby/3.3.0/bundler/gems/rdf-turtle-6506e92ccd8e/lib/rdf/turtle/writer.rb', line 522

def bump_reference(resource)
  @references[resource] = ref_count(resource) + 1
end

#collection(node, position) ⇒ Object (protected) 



546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
 
# File 'vendor/bundler/ruby/3.3.0/bundler/gems/rdf-turtle-6506e92ccd8e/lib/rdf/turtle/writer.rb', line 546

def collection(node, position)
  return false if !collection?(node)
  return false if position == :subject && ref_count(node) > 0
  return false if position == :object && prop_count(node) > 0
  #log_debug("collection") {"#{node.to_ntriples}, #{position}"}

  @output.write("(")
  log_depth do
    list = @lists[node]
    log_debug("collection") {list.inspect}
    subject_done(RDF.nil)
    index = 0
    list.each_statement do |st|
      next unless st.predicate == RDF.first
      log_debug {" list this: #{st.subject} first: #{st.object}[#{position}]"}
      @output.write(" ") if index > 0
      path(st.object, position)
      subject_done(st.subject)
      position = :object
      index += 1
    end
  end
  @output.write(')')
end

#collection?(l) ⇒ Boolean (protected)

Checks if l is a valid RDF list, i.e. no nodes have other properties.

Returns:

  • (Boolean) 


541
542
543
544
 
# File 'vendor/bundler/ruby/3.3.0/bundler/gems/rdf-turtle-6506e92ccd8e/lib/rdf/turtle/writer.rb', line 541

def collection?(l)
  #log_debug("collection?") {l.inspect}
  return @lists.key?(l)
end

#format_literal(literal, **options) ⇒ String

Returns the N-Triples representation of a literal.

Parameters:

Returns:



276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
 
# File 'vendor/bundler/ruby/3.3.0/bundler/gems/rdf-turtle-6506e92ccd8e/lib/rdf/turtle/writer.rb', line 276

def format_literal(literal, **options)
  case literal
  when RDF::Literal
    case @options[:literal_shorthand] && literal.valid? ? literal.datatype : false
    when RDF::XSD.boolean
      %w(true false).include?(literal.value) ? literal.value : literal.canonicalize.to_s
    when RDF::XSD.integer
      literal.value.match?(/^[\+\-]?\d+$/) && !canonicalize? ? literal.value : literal.canonicalize.to_s
    when RDF::XSD.decimal
      literal.value.match?(/^[\+\-]?\d+\.\d+?$/) && !canonicalize? ?
        literal.value :
        literal.canonicalize.to_s
    when RDF::XSD.double
      in_form = case literal.value
      when /[\+\-]?\d+\.\d*E[\+\-]?\d+$/i then true
      when /[\+\-]?\.\d+E[\+\-]?\d+$/i    then true
      when /[\+\-]?\d+E[\+\-]?\d+$/i      then true
      else false
      end && !canonicalize?

      in_form ? literal.value : literal.canonicalize.to_s.sub('E', 'e').to_s
    else
      text = quoted(literal.value)
      text << "@#{literal.language}" if literal.language?
      text << "--#{literal.direction}" if literal.direction?
      text << "^^#{format_uri(literal.datatype)}" if literal.datatype?
      text
    end
  else
    quoted(literal.to_s)
  end
end

#format_node(node, **options) ⇒ String

Returns the Turtle representation of a blank node.

Parameters:

Returns:



327
328
329
 
# File 'vendor/bundler/ruby/3.3.0/bundler/gems/rdf-turtle-6506e92ccd8e/lib/rdf/turtle/writer.rb', line 327

def format_node(node, **options)
  options[:unique_bnodes] ? node.to_unique_base : node.to_base
end

#format_tripleTerm(statement, **options) ⇒ String

Returns a triple term

Parameters:

Returns:



337
338
339
340
 
# File 'vendor/bundler/ruby/3.3.0/bundler/gems/rdf-turtle-6506e92ccd8e/lib/rdf/turtle/writer.rb', line 337

def format_tripleTerm(statement, **options)
  log_debug("tripleTerm") {"#{statement.to_ntriples}"}
  "<<(%s %s %s)>>" % statement.to_a.map { |value| format_term(value, **options) }
end

#format_uri(uri, **options) ⇒ String

Returns the Turtle representation of a URI reference.

Parameters:

Returns:



315
316
317
318
319
 
# File 'vendor/bundler/ruby/3.3.0/bundler/gems/rdf-turtle-6506e92ccd8e/lib/rdf/turtle/writer.rb', line 315

def format_uri(uri, **options)
  md = uri.relativize(base_uri)
  log_debug("relativize") {"#{uri.to_ntriples} => #{md.inspect}"} if md != uri.to_s
  md != uri.to_s ? "<#{md}>" : (get_pname(uri) || "<#{uri}>")
end

#get_pname(resource) ⇒ String?

Return a PName for the URI, or nil. Adds namespace of PName to defined prefixes

Parameters:

Returns:

  • (String, nil) —

    value to use to identify URI



207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
 
# File 'vendor/bundler/ruby/3.3.0/bundler/gems/rdf-turtle-6506e92ccd8e/lib/rdf/turtle/writer.rb', line 207

def get_pname(resource)
  case resource
  when RDF::Node
    return options[:unique_bnodes] ? resource.to_unique_base : resource.to_base
  when RDF::URI
    uri = resource.to_s
  else
    return nil
  end

  pname = case
  when @uri_to_pname.key?(uri)
    return @uri_to_pname[uri]
  when u = @uri_to_prefix.keys.sort_by {|uu| uu.length}.reverse.detect {|uu| uri.index(uu.to_s) == 0}
    # Use a defined prefix
    prefix = @uri_to_prefix[u]
    unless u.to_s.empty?
      prefix(prefix, u) unless u.to_s.empty?
      log_debug("get_pname") {"add prefix #{prefix.inspect} => #{u}"}
      # Escape suffix, as necessary
      RDF::URI(uri).pname(prefixes: {prefix => u})
    end
  when @options[:standard_prefixes] && vocab = RDF::Vocabulary.each.to_a.detect {|v| uri.index(v.to_uri.to_s) == 0}
    prefix = vocab.__name__.to_s.split('::').last.downcase
    @uri_to_prefix[vocab.to_uri.to_s] = prefix
    prefix(prefix, vocab.to_uri) # Define for output
    log_debug("get_pname") {"add standard prefix #{prefix.inspect} => #{vocab.to_uri}"}
    RDF::URI(uri).pname(prefixes: {prefix => vocab.to_uri})
  else
    nil
  end

  # Make sure pname is a valid pname
  if pname
    md = Terminals::PNAME_LN.match(pname) || Terminals::PNAME_NS.match(pname)
    pname = nil unless md.to_s.length == pname.length
  end

  @uri_to_pname[uri] = pname
end

#in_triple_term?(resource) ⇒ Boolean (protected)

Resource is used within a triple term

Returns:

  • (Boolean) 


536
537
538
 
# File 'vendor/bundler/ruby/3.3.0/bundler/gems/rdf-turtle-6506e92ccd8e/lib/rdf/turtle/writer.rb', line 536

def in_triple_term?(resource)
  @in_triple_term.key?(resource)
end

#indent(modifier = 0) ⇒ String (protected)

Returns indent string multiplied by the depth

Parameters:

  • modifier (Integer) (defaults to: 0) —

    Increase depth by specified amount

Returns:

  • (String) —

    A number of spaces, depending on current depth



474
475
476
 
# File 'vendor/bundler/ruby/3.3.0/bundler/gems/rdf-turtle-6506e92ccd8e/lib/rdf/turtle/writer.rb', line 474

def indent(modifier = 0)
  " " * (@options.fetch(:log_depth, log_depth) * 2 + modifier)
end

#is_done?(subject) ⇒ Boolean (protected)

Returns:

  • (Boolean) 


526
527
528
 
# File 'vendor/bundler/ruby/3.3.0/bundler/gems/rdf-turtle-6506e92ccd8e/lib/rdf/turtle/writer.rb', line 526

def is_done?(subject)
  @serialized.include?(subject)
end

#objectList(subject, predicate, objects) ⇒ Object (protected)

Render an objectList having a common subject and predicate



664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
 
# File 'vendor/bundler/ruby/3.3.0/bundler/gems/rdf-turtle-6506e92ccd8e/lib/rdf/turtle/writer.rb', line 664

def objectList(subject, predicate, objects)
  log_debug("objectList") {objects.inspect}
  return if objects.empty?

  objects.each_with_index do |obj, i|
    if i > 0 && blankNodePropertyList?(obj, :object)
      @output.write ", "
    elsif i > 0
      @output.write ",\n#{indent(4)}"
    end
    path(obj, :object)

    # If there is a single reifier for this statement, write that out
    tt = RDF::Statement(subject, predicate, obj)
    reifs = @reification.select {|k, v| v.include?(tt)}.keys
    if reifs.length == 1
      reif = reifs.first
      @as_reifiedTriple[reif] = true
      @output.write ' {| '
      predicateObjectList(reif, true)
      @output.write ' |}'
      subject_done(reif)
    end
  end
end

#order_subjects ⇒ Array<Resource> (protected)

Order subjects for output. Override this to output subjects in another order.

Uses #top_classes and #base_uri.

Returns:



366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
 
# File 'vendor/bundler/ruby/3.3.0/bundler/gems/rdf-turtle-6506e92ccd8e/lib/rdf/turtle/writer.rb', line 366

def order_subjects
  seen = {}
  subjects = []

  # Start with base_uri
  if base_uri && @subjects.key?(base_uri)
    subjects << RDF::URI(base_uri)
    seen[RDF::URI(base_uri)] = true
  end

  # Add distinguished classes
  top_classes.each do |class_uri|
    graph.query({predicate:  RDF.type, object:  class_uri}).
      map {|st| st.subject}.
      sort.
      uniq.
      each do |subject|
      log_debug("order_subjects") {subject.to_ntriples}
      subjects << subject
      seen[subject] = true
    end
  end

  # Mark as seen lists that are part of another list
  @lists.values.map(&:statements).
    flatten.each do |st|
      seen[st.object] = true if @lists.key?(st.object)
    end

  # List elements which are bnodes should not be targets for top-level serialization
  list_elements = @lists.values.map(&:to_a).flatten.select(&:node?).compact

  # Sort subjects by resources and statements over bnodes, ref_counts and the subject URI itself
  recursable = (@subjects.keys - list_elements).
    select {|s| !seen.include?(s)}.
    map {|r| [r.node? ? 2 : (r.statement? ? 1 : 0), ref_count(r), r]}.
    sort

  # Sort recursable unto those that are not reifiers and those that are, so that reifieres come last.
  subjects + recursable.map{|r| r.last}.partition {|r| !@reification.key?(r)}.flatten
end

#p_term(resource, position) ⇒ Object (protected)

Default singular resource representation.



627
628
629
630
631
632
633
634
635
 
# File 'vendor/bundler/ruby/3.3.0/bundler/gems/rdf-turtle-6506e92ccd8e/lib/rdf/turtle/writer.rb', line 627

def p_term(resource, position)
  #log_debug("p_term") {"#{resource.to_ntriples}, #{position}"}
  l = if resource == RDF.nil
    "()"
  else
    format_term(resource, **options)
  end
  @output.write(l)
end

#path(resource, position) ⇒ Object (protected)

Represent a resource in subject, predicate or object position. Use either collection, blankNodePropertyList or singular resource notation.

Raises:



639
640
641
642
643
644
645
646
647
648
649
650
651
652
 
# File 'vendor/bundler/ruby/3.3.0/bundler/gems/rdf-turtle-6506e92ccd8e/lib/rdf/turtle/writer.rb', line 639

def path(resource, position)
  log_debug("path") do
    "#{resource.to_ntriples}, " +
    "pos: #{position}, " +
    "()?: #{collection?(resource)}, " +
    "[]?: #{blankNodePropertyList?(resource, position)}, " +
    "rc: #{ref_count(resource)}"
  end
  raise RDF::WriterError, "Cannot serialize resource '#{resource}'" unless
    collection(resource, position) ||
    reifiedTriple(resource, position) ||
    blankNodePropertyList(resource, position) ||
    p_term(resource, position)
end

#predicate(resource) ⇒ Object (protected) 



654
655
656
657
658
659
660
661
 
# File 'vendor/bundler/ruby/3.3.0/bundler/gems/rdf-turtle-6506e92ccd8e/lib/rdf/turtle/writer.rb', line 654

def predicate(resource)
  log_debug("predicate") {resource.to_ntriples}
  if resource == RDF.type
    @output.write("a")
  else
    path(resource, :predicate)
  end
end

#predicate_order ⇒ Array<URI> (protected)

Defines order of predicates to to emit at begninning of a resource description. Defaults to \[rdf:type, rdfs:label, dc:title\]

Returns:



360
 
# File 'vendor/bundler/ruby/3.3.0/bundler/gems/rdf-turtle-6506e92ccd8e/lib/rdf/turtle/writer.rb', line 360

def predicate_order; [RDF.type, RDF::RDFS.label, RDF::URI("http://purl.org/dc/terms/title")]; end

#predicateObjectList(subject, from_bpl = false) ⇒ Integer (protected)

Render a predicateObjectList having a common subject.

Returns:

  • (Integer) —

    the number of properties serialized



692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
 
# File 'vendor/bundler/ruby/3.3.0/bundler/gems/rdf-turtle-6506e92ccd8e/lib/rdf/turtle/writer.rb', line 692

def predicateObjectList(subject, from_bpl = false)
  properties = @subjects.fetch(subject, {})

  prop_list = sort_properties(properties)
  prop_list -= [RDF.first, RDF.rest] if @lists.key?(subject)
  prop_list -= [RDF.reifies] if @as_reifiedTriple.key?(subject)
  log_debug("predicateObjectList") {prop_list.inspect}
  return 0 if prop_list.empty?

  @output.write("\n#{indent(2)}") if properties.keys.length > 1 && from_bpl
  prop_list.each_with_index do |prop, i|
    begin
      @output.write(";\n#{indent(2)}") if i > 0
      predicate(prop)
      @output.write(" ")
      objectList(subject, prop, properties[prop])
    end
  end
  properties.keys.length
end

#preprocess ⇒ Object (protected)

Perform any preprocessing of statements required



409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
 
# File 'vendor/bundler/ruby/3.3.0/bundler/gems/rdf-turtle-6506e92ccd8e/lib/rdf/turtle/writer.rb', line 409

def preprocess
  # Load defined prefixes
  (@options[:prefixes] || {}).each_pair do |k, v|
    @uri_to_prefix[v.to_s] = k
  end

  prefix(nil, @options[:default_namespace]) if @options[:default_namespace]

  case
  when @options[:stream]
  else
    @options[:prefixes] = {}  # Will define actual used when matched

    @graph.each {|statement| preprocess_statement(statement)}
  end
end

#preprocess_statement(statement, as_subject: true) ⇒ Object (protected)

Perform any statement preprocessing required. This is used to perform reference counts and determine required prefixes.

Parameters:

  • statement (Statement)
  • as_subject (Boolean) (defaults to: true) —

    Count as a graph subject



430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
 
# File 'vendor/bundler/ruby/3.3.0/bundler/gems/rdf-turtle-6506e92ccd8e/lib/rdf/turtle/writer.rb', line 430

def preprocess_statement(statement, as_subject: true)
  #log_debug("preprocess") {statement.to_ntriples}
  bump_reference(statement.object)

  # Also count references of triple terms
  preprocess_statement(statement.object, as_subject: false) if statement.object.statement?

  # Count properties of this subject
  if as_subject
    (@subjects[statement.subject] ||= {})[statement.predicate] ||= []
    @subjects[statement.subject][statement.predicate] << statement.object
  else
    # Terms of statement are in triple terms
    statement.to_a.each {|t| @in_triple_term[t] = true}
  end

  # If it fits, allow this to be rendered as a reifiedTriple
  if statement.object.statement? && statement.predicate == RDF.reifies
    @reification[statement.subject] ||= []
    @reification[statement.subject] << statement.object unless
      @reification[statement.subject].include?(statement.object)
  end

  # Collect lists
  if statement.predicate == RDF.first
    l = RDF::List.new(subject: statement.subject, graph: graph)
    @lists[statement.subject] = l if l.valid?
  end

  if statement.object == RDF.nil || statement.subject == RDF.nil
    # Add an entry for the list tail
    @lists[RDF.nil] ||= RDF::List[]
  end

  # Pre-fetch pnames, to fill prefixes
  get_pname(statement.subject)
  get_pname(statement.predicate)
  get_pname(statement.object)
  get_pname(statement.object.datatype) if statement.object.literal? && statement.object.datatype
end

#prop_count(subject) ⇒ Integer (protected)

Return the number of statements having this resource as a subject other than for list properties

Returns:



507
508
509
510
511
 
# File 'vendor/bundler/ruby/3.3.0/bundler/gems/rdf-turtle-6506e92ccd8e/lib/rdf/turtle/writer.rb', line 507

def prop_count(subject)
  @subjects.fetch(subject, {}).
    reject {|p, o| [RDF.type, RDF.first, RDF.rest, RDF.reifies].include?(p)}.
    values.flatten.length
end

#quoted(string) ⇒ String (protected)

Use single- or multi-line quotes. If literal contains \t, \n, or \r, use a multiline quote, otherwise, use a single-line

Parameters:

Returns:



495
496
497
498
499
500
501
502
503
 
# File 'vendor/bundler/ruby/3.3.0/bundler/gems/rdf-turtle-6506e92ccd8e/lib/rdf/turtle/writer.rb', line 495

def quoted(string)
  if string.to_s.match(/[\t\n\r]/)
    string = string.gsub('\\', '\\\\\\\\').gsub('"', '\\"')

    %("""#{string}""")
  else
    "\"#{escaped(string)}\""
  end
end

#ref_count(resource) ⇒ Integer (protected)

Return the number of times this node has been referenced in the object position

Returns:



515
516
517
 
# File 'vendor/bundler/ruby/3.3.0/bundler/gems/rdf-turtle-6506e92ccd8e/lib/rdf/turtle/writer.rb', line 515

def ref_count(resource)
  @references.fetch(resource, 0)
end

#reifiedTriple(resource, position) ⇒ Object (protected)

Render a reifiedTriple



600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
 
# File 'vendor/bundler/ruby/3.3.0/bundler/gems/rdf-turtle-6506e92ccd8e/lib/rdf/turtle/writer.rb', line 600

def reifiedTriple(resource, position)
  return false unless reifiedTriple?(resource, position)
  write_id = resource.iri? || ref_count(resource) > 1
  @as_reifiedTriple[resource] = true  # Prevent rdf:reifies from being emitted

  log_debug("reifiedTriple") {resource.to_ntriples}
  subject_done(resource)
  # There may be multiple reifiedTriples using this resource
  @reification[resource].each do |tt|
    @output.write(position == :subject ? "\n#{indent} << " : '<< ')
    reifiedTriple(tt.subject, :object) || p_term(tt.subject, :object)
    @output.write(' ')
    predicate(tt.predicate)
    @output.write(' ')
    reifiedTriple(tt.object, :object) || p_term(tt.object, :object)

    if write_id
      # Only need to output blank node identifiers if they have more than one reference
      @output.write(' ~')
      p_term(resource, :subject)
    end
    @output.write(' >>')
  end
  true
end

#reifiedTriple?(resource, position) ⇒ Boolean (protected)

Is this a reifiedTriple?

Returns:

  • (Boolean) 


594
595
596
597
 
# File 'vendor/bundler/ruby/3.3.0/bundler/gems/rdf-turtle-6506e92ccd8e/lib/rdf/turtle/writer.rb', line 594

def reifiedTriple?(resource, position)
  @reification.key?(resource) &&
  (position == :subject ? (prop_count(resource) > 0) : (prop_count(resource) == 0))
end

#reset ⇒ Object (protected)

Reset internal helper instance variables



479
480
481
482
483
484
485
486
487
488
 
# File 'vendor/bundler/ruby/3.3.0/bundler/gems/rdf-turtle-6506e92ccd8e/lib/rdf/turtle/writer.rb', line 479

def reset
  @lists = {}

  @references = {}
  @serialized = {}
  @subjects = {}
  @reification = {}
  @as_reifiedTriple = {}
  @in_triple_term = {}
end

#sort_properties(properties) ⇒ Array<RDF::URI>

Take a hash from predicate uris to lists of values. Sort the lists of values. Return a sorted list of properties.

Parameters:

Returns:

  • (Array<RDF::URI>) —

    ] Ordered list of properties. Uses predicate_order.



252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
 
# File 'vendor/bundler/ruby/3.3.0/bundler/gems/rdf-turtle-6506e92ccd8e/lib/rdf/turtle/writer.rb', line 252

def sort_properties(properties)
  # Make sorted list of properties
  prop_list = []

  predicate_order.each do |prop|
    next unless properties[prop]
    prop_list << prop
  end

  properties.keys.sort.each do |prop|
    next if prop_list.include?(prop)
    prop_list << prop
  end

  log_debug("sort_properties") {prop_list.join(', ')}
  prop_list
end

#start_document ⇒ Object (protected)

Output @base and @prefix definitions



344
345
346
347
348
349
350
351
 
# File 'vendor/bundler/ruby/3.3.0/bundler/gems/rdf-turtle-6506e92ccd8e/lib/rdf/turtle/writer.rb', line 344

def start_document
  @output.write("#{indent}@base <#{base_uri}> .\n") unless base_uri.to_s.empty?

  log_debug("start_document") {prefixes.inspect}
  prefixes.keys.sort_by(&:to_s).each do |prefix|
    @output.write("#{indent}@prefix #{prefix}: <#{prefixes[prefix]}> .\n")
  end
end

#statement(subject) ⇒ Object (protected) 



723
724
725
726
727
728
 
# File 'vendor/bundler/ruby/3.3.0/bundler/gems/rdf-turtle-6506e92ccd8e/lib/rdf/turtle/writer.rb', line 723

def statement(subject)
  log_debug("statement") {"#{subject.to_ntriples}, bnodePL?: #{blankNodePropertyList?(subject, :subject)}"}
  subject_done(subject)
  blankNodePropertyList(subject, :subject) || triples(subject)
  @output.puts
end

#subject_done(subject) ⇒ Object (protected)

Mark a subject as done.



531
532
533
 
# File 'vendor/bundler/ruby/3.3.0/bundler/gems/rdf-turtle-6506e92ccd8e/lib/rdf/turtle/writer.rb', line 531

def subject_done(subject)
  @serialized[subject] = true
end

#top_classes ⇒ Array<URI> (protected)

Defines rdf:type of subjects to be emitted at the beginning of the graph. Defaults to rdfs:Class

Returns:



355
 
# File 'vendor/bundler/ruby/3.3.0/bundler/gems/rdf-turtle-6506e92ccd8e/lib/rdf/turtle/writer.rb', line 355

def top_classes; [RDF::RDFS.Class]; end

#triples(subject) ⇒ Object (protected)

Render triples having the same subject using an explicit subject



714
715
716
717
718
719
720
721
 
# File 'vendor/bundler/ruby/3.3.0/bundler/gems/rdf-turtle-6506e92ccd8e/lib/rdf/turtle/writer.rb', line 714

def triples(subject)
  @output.write("\n#{indent}")
  path(subject, :subject)
  @output.write(" ")
  num_props = predicateObjectList(subject)
  @output.write("#{num_props > 0 ? ' ' : ''}.")
  true
end

#write_epilogue

This method returns an undefined value.

Outputs the Turtle representation of all stored triples.

See Also:



174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
 
# File 'vendor/bundler/ruby/3.3.0/bundler/gems/rdf-turtle-6506e92ccd8e/lib/rdf/turtle/writer.rb', line 174

def write_epilogue
  case
  when @options[:stream]
    stream_epilogue
  else
    @max_depth = @options[:max_depth] || 3

    self.reset

    log_debug("\nserialize") {"graph: #{@graph.size}"}

    preprocess

    start_document

    # Remove lists that are referenced and have non-list properties;
    # these are legal, but can't be serialized as lists
    @lists.reject! do |node, list|
      ref_count(node) > 0 && prop_count(node) > 0
    end

    order_subjects.each do |subject|
      unless is_done?(subject)
        statement(subject)
      end
    end
  end
  super
end

#write_prologue

This method returns an undefined value.

Write out declarations



160
161
162
163
164
165
166
167
 
# File 'vendor/bundler/ruby/3.3.0/bundler/gems/rdf-turtle-6506e92ccd8e/lib/rdf/turtle/writer.rb', line 160

def write_prologue
  case
  when @options[:stream]
    stream_prologue
  else
  end
  super
end

#write_triple(subject, predicate, object)

This method returns an undefined value.

Adds a triple to be serialized

Parameters:



148
149
150
151
152
153
154
155
 
# File 'vendor/bundler/ruby/3.3.0/bundler/gems/rdf-turtle-6506e92ccd8e/lib/rdf/turtle/writer.rb', line 148

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