Class: RDF::Node

Inherits:
Object show all
Includes:
Resource
Defined in:
vendor/bundler/ruby/2.4.0/bundler/gems/rdf-da525ad24ff7/lib/rdf/model/node.rb,
vendor/bundler/ruby/2.4.0/bundler/gems/rdf-spec-7e186ad0cd77/lib/rdf/spec/inspects.rb,
vendor/bundler/ruby/2.4.0/bundler/gems/json-ld-4e9cdb2fc35e/lib/json/ld/extensions.rb

Overview

An RDF blank node, also known as an anonymous or unlabeled node.

Examples:

Creating a blank node with an implicit identifier

bnode = RDF::Node.new

Creating a blank node with an UUID identifier

bnode = RDF::Node.uuid
bnode.to_s #=> "_:504c0a30-0d11-012d-3f50-001b63cac539"

Constant Summary

CACHE_SIZE =
Note:

caching interned nodes means that two different invocations using the same symbol will result in the same node, which may not be appropriate depending on the graph from which it is used. RDF requires that bnodes with the same label are, in fact, different bnodes, unless they are used within the same document.

Defines the maximum number of interned Node references that can be held cached in memory at any one time.

-1 # unlimited by default

Instance Attribute Summary collapse

Class Method Summary collapse

Instance Method Summary collapse

Methods included from Resource

new, #resource?

Methods included from Term

#<=>, #aggregate?, #compatible?, #escape, #evaluate, #ndvars, #term?, #to_base, #to_term, #vars

Methods included from SPARQL::Algebra::Expression

cast, #constant?, #evaluate, extension, extensions, for, #invalid?, new, open, #optimize, parse, register_extension, #to_sxp_bin, #valid?, #validate!, #variable?

Methods included from Value

#canonicalize, #canonicalize!, #constant?, #graph?, #inspect!, #invalid?, #iri?, #list?, #literal?, #resource?, #start_with?, #statement?, #term?, #to_nquads, #to_ntriples, #to_rdf, #to_term, #type_error, #uri?, #valid?, #validate!, #variable?

Constructor Details

#initialize(id = nil) ⇒ Node

Returns a new instance of Node

Parameters:

  • id (#to_s) (defaults to: nil)


92
93
94
95
# File 'vendor/bundler/ruby/2.4.0/bundler/gems/rdf-da525ad24ff7/lib/rdf/model/node.rb', line 92

def initialize(id = nil)
  id = nil if id.to_s.empty?
  @id = (id || "g#{__id__.to_i.abs}").to_s.freeze
end

Instance Attribute Details

#idString

Returns:



88
89
90
# File 'vendor/bundler/ruby/2.4.0/bundler/gems/rdf-da525ad24ff7/lib/rdf/model/node.rb', line 88

def id
  @id
end

#originalRDF::Node

Originally instantiated node, if any

Returns:



85
86
87
# File 'vendor/bundler/ruby/2.4.0/bundler/gems/rdf-da525ad24ff7/lib/rdf/model/node.rb', line 85

def original
  @original
end

Class Method Details

.uuid(format: :default, grammar: nil) ⇒ RDF::Node

Returns a blank node with a random UUID-based identifier.

(Depends on availability of either uuid or uuidtools gems).

Formats supported by the UUID generator:

  • :default Produces 36 characters, including hyphens separating the UUID value parts
  • :compact Produces a 32 digits (hexadecimal) value with no hyphens
  • :urn Adds the prefix urn:uuid: to the default format Requires that the uuid gem be loadable to use format

Parameters:

  • format (:default, :compact)

    (:default)

  • grammar (Regexp)

    (nil) a grammar specification that the generated UUID must match The UUID is generated such that its initial part is guaranteed to match the given grammar, e.g. /^[A-Za-z][A-Za-z0-9]*/. Some RDF storage systems (e.g. AllegroGraph) require this.

Returns:



47
48
49
50
51
52
53
54
55
56
57
# File 'vendor/bundler/ruby/2.4.0/bundler/gems/rdf-da525ad24ff7/lib/rdf/model/node.rb', line 47

def self.uuid(format: :default, grammar: nil)
  case
    when grammar
      warn "[DEPRECATION] The grammar parameter to RDF::Node#uri is deprecated.\n" +
           "Called from #{Gem.location_of_caller.join(':')}"
      uuid = RDF::Util::UUID.generate(format: format) until uuid =~ grammar
    else
      uuid = RDF::Util::UUID.generate(format: format)
  end
  self.new(uuid)
end

Instance Method Details

#+(value) ⇒ Object

Odd case of appending to a BNode identifier



6
7
8
# File 'vendor/bundler/ruby/2.4.0/bundler/gems/json-ld-4e9cdb2fc35e/lib/json/ld/extensions.rb', line 6

def +(value)
  Node.new(id + value.to_s)
end

#==(other) ⇒ Boolean Also known as: ===

Checks whether this blank node is equal to other (type checking).

In this case, different nodes having the same id are considered the same.

Per SPARQL data-r2/expr-equal/eq-2-2, numeric can't be compared with other types

Parameters:

Returns:

  • (Boolean)

See Also:



152
153
154
155
156
157
158
159
160
161
# File 'vendor/bundler/ruby/2.4.0/bundler/gems/rdf-da525ad24ff7/lib/rdf/model/node.rb', line 152

def ==(other)
  if other.is_a?(Literal)
    # If other is a Literal, reverse test to consolodate complex type checking logic
    other == self
  else
    other.respond_to?(:node?) && other.node? &&
      self.hash == other.to_term.hash &&
      other.respond_to?(:id) && @id == other.to_term.id
  end
end

#anonymous?Boolean Also known as: unlabeled?

Returns true.

Returns:

  • (Boolean)


109
110
111
# File 'vendor/bundler/ruby/2.4.0/bundler/gems/rdf-da525ad24ff7/lib/rdf/model/node.rb', line 109

def anonymous?
  true
end

#dupRDF::Node

Override #dup to remember original object. This allows .eql? to determine that two nodes are the same thing, and not different nodes instantiated with the same identifier.

Returns:



76
77
78
79
80
# File 'vendor/bundler/ruby/2.4.0/bundler/gems/rdf-da525ad24ff7/lib/rdf/model/node.rb', line 76

def dup
  node = super
  node.original = self.original || self
  node
end

#eql?(other) ⇒ Boolean

Determines if self is the same term as other.

In this case, nodes must be the same object

Parameters:

Returns:

  • (Boolean)


138
139
140
# File 'vendor/bundler/ruby/2.4.0/bundler/gems/rdf-da525ad24ff7/lib/rdf/model/node.rb', line 138

def eql?(other)
  other.is_a?(RDF::Node) && (self.original || self).equal?(other.original || other)
end

#hashInteger

Returns a hash code for this blank node.

Returns:



127
128
129
# File 'vendor/bundler/ruby/2.4.0/bundler/gems/rdf-da525ad24ff7/lib/rdf/model/node.rb', line 127

def hash
  @id.hash
end

#inspectObject



17
18
19
# File 'vendor/bundler/ruby/2.4.0/bundler/gems/rdf-spec-7e186ad0cd77/lib/rdf/spec/inspects.rb', line 17

def inspect
  "RDF::Node(#{to_base})"
end

#labeled?Boolean

Returns false.

Returns:

  • (Boolean)


119
120
121
# File 'vendor/bundler/ruby/2.4.0/bundler/gems/rdf-da525ad24ff7/lib/rdf/model/node.rb', line 119

def labeled?
  !unlabeled?
end

#make_unique!self

Make this term identifier unique, if it is found to be shared with another node having the same identifier

Returns:

  • (self)


175
176
177
178
# File 'vendor/bundler/ruby/2.4.0/bundler/gems/rdf-da525ad24ff7/lib/rdf/model/node.rb', line 175

def make_unique!
  @id = to_unique_base[2..-1]
  self
end

#node?Boolean

Returns true.

Returns:

  • (Boolean)


101
102
103
# File 'vendor/bundler/ruby/2.4.0/bundler/gems/rdf-da525ad24ff7/lib/rdf/model/node.rb', line 101

def node?
  true
end

#to_sString

Returns a string representation of this blank node.

Returns:



184
185
186
# File 'vendor/bundler/ruby/2.4.0/bundler/gems/rdf-da525ad24ff7/lib/rdf/model/node.rb', line 184

def to_s
  "_:%s" % @id.to_s
end

#to_symSymbol

Returns a symbol representation of this blank node.

Returns:

Since:

  • 0.2.0



193
194
195
# File 'vendor/bundler/ruby/2.4.0/bundler/gems/rdf-da525ad24ff7/lib/rdf/model/node.rb', line 193

def to_sym
  @id.to_s.to_sym
end

#to_unique_baseString

Returns a representation of this node independent of any identifier used to initialize it

Returns:



168
169
170
# File 'vendor/bundler/ruby/2.4.0/bundler/gems/rdf-da525ad24ff7/lib/rdf/model/node.rb', line 168

def to_unique_base
  original ? original.to_unique_base :  "_:g#{__id__.to_i.abs}"
end