Class: RdfContext::BNode

Inherits:
Resource show all
Defined in:
lib/rdf_context/bnode.rb

Overview

The BNode class creates RDF blank nodes.

Instance Attribute Summary collapse

Class Method Summary collapse

Instance Method Summary collapse

Methods inherited from Resource

#graph?, #literal?, #resource?, #uri?

Constructor Details

#initialize(identifier = nil, context = {}) ⇒ BNode

Create a new BNode, optionally accept a identifier for the BNode. Otherwise, generated sequentially.

A BNode may have a bank (empty string) identifier, which will be equivalent to another blank identified BNode.

Identifiers only have meaning within a particular parsing context, and are used to lookup previoiusly defined BNodes using the same identifier. Names are not preserved within the underlying storage model.

Parameters:

  • identifier (String) (defaults to: nil) —

    (nil) Legal NCName or nil for a named BNode

  • context (Hash) (defaults to: {}) —

    ({}) Context used to store named BNodes



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# File 'lib/rdf_context/bnode.rb', line 18

def initialize(identifier = nil, context = {})
  if identifier.nil?
    @identifier = generate_bn_identifier
  elsif identifier.match(/n?bn\d+[a-z]+(N\w+)?$/)
    @identifier = context[identifier] || identifier
  elsif self.valid_id?(identifier)
    @identifier = context[identifier] ||= generate_bn_identifier(identifier)
  else
    @identifier = generate_bn_identifier
  end
end

Instance Attribute Details

#identifier ⇒ Object

The identifier used used for this BNode.



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# File 'lib/rdf_context/bnode.rb', line 71

def identifier
  @identifier
end

Class Method Details

.parse(str) ⇒ Object

Parse a BNode



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# File 'lib/rdf_context/bnode.rb', line 31

def self.parse(str)
  BNode.new($1) if str =~ /^_:(.*)$/
end

Instance Method Details

#<=>(other) ⇒ Object 



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# File 'lib/rdf_context/bnode.rb', line 86

def <=>(other)
  self.to_s <=> other.to_s
end

#bnode? ⇒ Boolean

Returns ‘true`

Returns:

  • (Boolean) 


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# File 'lib/rdf_context/bnode.rb', line 39

def bnode?
  true
end

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

Compare BNodes. BNodes are equivalent if they have the same identifier

Returns:

  • (Boolean) 


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# File 'lib/rdf_context/bnode.rb', line 76

def eql?(other)
  case other
  when BNode
    other.identifier == self.identifier
  else
    self.identifier == other.to_s
  end
end

#generate_bn_identifier(name = nil) ⇒ Object (protected)

Generate a unique identifier (time with milliseconds plus generated increment)



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# File 'lib/rdf_context/bnode.rb', line 103

def generate_bn_identifier(name = nil)
  @@base ||= "bn#{(Time.now.to_f * 1000).to_i}"
  @@next_generated ||= "a"
  if name
    bn = "n#{@@base}#{@@next_generated}N#{name}"
  else
    bn = "#{@@base}#{@@next_generated}"
  end
  @@next_generated = @@next_generated.succ
  bn
end

#hash ⇒ Object

Needed for uniq



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# File 'lib/rdf_context/bnode.rb', line 91

def hash; self.to_s.hash; end

#inspect ⇒ Object 



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# File 'lib/rdf_context/bnode.rb', line 93

def inspect
  "#{self.class}[#{self.to_n3}]"
end

#to_n3 ⇒ String Also known as: to_ntriples

Exports the BNode in N-Triples form.

Example

b = BNode.new; b.to_n3  # => returns a string of the BNode in n3 form

Returns:

  • (String) —

    The BNode in n3.

Author:

  • Tom Morris



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# File 'lib/rdf_context/bnode.rb', line 57

def to_n3
  "_:#{self.identifier}"
end

#to_s ⇒ Object

Return BNode identifier



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# File 'lib/rdf_context/bnode.rb', line 44

def to_s
  return self.identifier.to_s
end

#valid_id?(name) ⇒ Boolean (protected)

Returns:

  • (Boolean) 


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# File 'lib/rdf_context/bnode.rb', line 98

def valid_id?(name)
  NC_REGEXP.match(name) || name.empty?
end

#xml_args ⇒ Object

Output URI as resource reference for RDF/XML

Example

b = BNode.new("foo"); b.xml_args  # => [{"rdf:nodeID" => "foo"}]



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# File 'lib/rdf_context/bnode.rb', line 66

def xml_args
  [{"rdf:nodeID" => self.identifier}]
end