Class: RDF::Reader Abstract

Inherits:
Object
  • Object
show all
Extended by:
Enumerable, Util::Aliasing::LateBound
Includes:
Enumerable, Readable
Defined in:
lib/rdf/reader.rb

Overview

This class is abstract.

The base class for RDF parsers.

Examples:

Loading an RDF reader implementation

require 'rdf/ntriples'

Iterating over known RDF reader classes

RDF::Reader.each { |klass| puts klass.name }

Obtaining an RDF reader class

RDF::Reader.for(:ntriples)     #=> RDF::NTriples::Reader
RDF::Reader.for("etc/doap.nt")
RDF::Reader.for(:file_name      => "etc/doap.nt")
RDF::Reader.for(:file_extension => "nt")
RDF::Reader.for(:content_type   => "text/plain")

Instantiating an RDF reader class

RDF::Reader.for(:ntriples).new($stdin) { |reader| ... }

Parsing RDF statements from a file

RDF::Reader.open("etc/doap.nt") do |reader|
  reader.each_statement do |statement|
    puts statement.inspect
  end
end

Parsing RDF statements from a string

data = StringIO.new(File.read("etc/doap.nt"))
RDF::Reader.for(:ntriples).new(data) do |reader|
  reader.each_statement do |statement|
    puts statement.inspect
  end
end

See Also:

Direct Known Subclasses

NTriples::Reader

Instance Attribute Summary collapse

Class Method Summary collapse

Instance Method Summary collapse

Methods included from Util::Aliasing::LateBound

alias_method

Methods included from Enumerable

#contexts, #dump, #each_context, #each_graph, #each_object, #each_predicate, #each_quad, #each_subject, #enum_context, #enum_graph, #enum_object, #enum_predicate, #enum_quad, #enum_statement, #enum_subject, #enum_triple, #has_context?, #has_object?, #has_predicate?, #has_quad?, #has_statement?, #has_subject?, #has_triple?, #objects, #predicates, #quads, #statements, #subjects, #supports?, #to_a, #to_hash, #to_set, #triples

Methods included from Countable

#count, #empty?, #enum_for

Methods included from Readable

#readable?

Constructor Details

#initialize(input = $stdin, options = {}) {|reader| ... } ⇒ Reader

Initializes the reader.

Parameters:

  • input (IO, File, String) (defaults to: $stdin) —

    the input stream to read

  • options (Hash{Symbol => Object}) (defaults to: {}) —

    any additional options

Options Hash (options):

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

    the encoding of the input stream (Ruby 1.9+)

  • :validate (Boolean) — default: false —

    whether to validate the parsed statements and values

  • :canonicalize (Boolean) — default: false —

    whether to canonicalize parsed literals

  • :intern (Boolean) — default: true —

    whether to intern all parsed URIs

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

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

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

    the base URI to use when resolving relative URIs (not supported by all readers)

Yields:

  • (reader) —

    ‘self`

Yield Parameters:

Yield Returns:

  • (void) —

    ignored



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# File 'lib/rdf/reader.rb', line 185

def initialize(input = $stdin, options = {}, &block)
  @options = options.dup
  @options[:validate]     ||= false
  @options[:canonicalize] ||= false
  @options[:intern]       ||= true
  @options[:prefixes]     ||= Hash.new

  @input = case input
    when String then StringIO.new(input)
    else input
  end

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

Instance Attribute Details

#options ⇒ Hash (readonly)

Any additional options for this reader.

Returns:

  • (Hash)

Since:

  • 0.3.0



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# File 'lib/rdf/reader.rb', line 210

def options
  @options
end

Class Method Details

.each {|klass| ... } ⇒ Enumerator

Enumerates known RDF reader classes.

Yields:

  • (klass)

Yield Parameters:

  • klass (Class)

Returns:



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# File 'lib/rdf/reader.rb', line 51

def self.each(&block)
  @@subclasses.each(&block)
end

.for(format) ⇒ Class .for(filename) ⇒ Class .for(options = {}) ⇒ Class

Finds an RDF reader class based on the given criteria.

If the reader class has a defined format, use that.

Overloads:

  • .for(format) ⇒ Class

    Finds an RDF reader class based on a symbolic name.

    Parameters:

    • format (Symbol)

    Returns:

    • (Class)
  • .for(filename) ⇒ Class

    Finds an RDF reader class based on a file name.

    Parameters:

    • filename (String)

    Returns:

    • (Class)
  • .for(options = {}) ⇒ Class

    Finds an RDF reader class based on various options.

    Parameters:

    • options (Hash{Symbol => Object}) (defaults to: {})

    Options Hash (options):

    • :file_name (String, #to_s) — default: nil
    • :file_extension (Symbol, #to_sym) — default: nil
    • :content_type (String, #to_s) — default: nil
    • :sample (String) — default: nil —

      A sample of input used for performing format detection. If we find no formats, or we find more than one, and we have a sample, we can perform format detection to find a specific format to use, in which case we pick the first one we find

    Yield Returns:

    • (String) —

      another way to provide a sample, allows lazy for retrieving the sample.

    Returns:

    • (Class)
    • (Class)

Returns:

  • (Class) 


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# File 'lib/rdf/reader.rb', line 89

def self.for(options = {}, &block)
  options = options.merge(:has_reader => true) if options.is_a?(Hash)
  if format = self.format || Format.for(options, &block)
    format.reader
  end
end

.format(klass = nil) ⇒ Class Also known as: format_class

Retrieves the RDF serialization format class for this reader class.

Returns:

  • (Class) 


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# File 'lib/rdf/reader.rb', line 100

def self.format(klass = nil)
  if klass.nil?
    Format.each do |format|
      if format.reader == self
        return format
      end
    end
    nil # not found
  end
end

.open(filename, options = {}) {|reader| ... } ⇒ Object

Parses input from the given file name or URL.

Parameters:

  • filename (String, #to_s)
  • options (Hash{Symbol => Object}) (defaults to: {}) —

    any additional options (see #initialize and Format.for)

Options Hash (options):

  • :format (Symbol) — default: :ntriples

Yields:

  • (reader)

Yield Parameters:

Yield Returns:

  • (void) —

    ignored

Raises:



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# File 'lib/rdf/reader.rb', line 126

def self.open(filename, options = {}, &block)
  Util::File.open_file(filename, options) do |file|
    format_options = options.dup
    format_options[:content_type] ||= file.content_type if file.respond_to?(:content_type)
    format_options[:file_name] ||= filename
    reader = self.for(format_options[:format] || format_options) do
      # Return a sample from the input file
      sample = file.read(1000)
      file.rewind
      sample
    end
    if reader
      reader.new(file, options, &block)
    else
      raise FormatError, "unknown RDF format: #{format_options.inspect}"
    end
  end
end

.to_sym ⇒ Symbol

Returns a symbol appropriate to use with RDF::Reader.for()

Returns:

  • (Symbol) 


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# File 'lib/rdf/reader.rb', line 148

def self.to_sym
  elements = self.to_s.split("::")
  sym = elements.pop
  sym = elements.pop if sym == 'Reader'
  sym.downcase.to_s.to_sym
end

Instance Method Details

#base_uri ⇒ Hash{Symbol => RDF::URI}

Returns the base URI determined by this reader.

Examples:

reader.prefixes[:dc]  #=> RDF::URI('http://purl.org/dc/terms/')

Returns:

Since:

  • 0.3.0



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# File 'lib/rdf/reader.rb', line 220

def base_uri
  @options[:base_uri]
end

#close ⇒ void Also known as: close!

This method returns an undefined value.

Closes the input stream, after which an ‘IOError` will be raised for further read attempts.

If the input stream is already closed, does nothing.

See Also:

Since:

  • 0.2.2



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# File 'lib/rdf/reader.rb', line 359

def close
  @input.close unless @input.closed?
end

#each_statement {|statement| ... } ⇒ void #each_statement ⇒ Enumerator Also known as: each

This method returns an undefined value.

Iterates the given block for each RDF statement.

If no block was given, returns an enumerator.

Statements are yielded in the order that they are read from the input stream.

Overloads:

  • #each_statement {|statement| ... } ⇒ void

    This method returns an undefined value.

    Yields:

    • (statement) —

      each statement

    Yield Parameters:

    Yield Returns:

    • (void) —

      ignored

  • #each_statement ⇒ Enumerator

    Returns:

See Also:



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# File 'lib/rdf/reader.rb', line 294

def each_statement(&block)
  if block_given?
    begin
      loop { block.call(read_statement) }
    rescue EOFError => e
      rewind rescue nil
    end
  end
  enum_for(:each_statement)
end

#each_triple {|subject, predicate, object| ... } ⇒ void #each_triple ⇒ Enumerator

This method returns an undefined value.

Iterates the given block for each RDF triple.

If no block was given, returns an enumerator.

Triples are yielded in the order that they are read from the input stream.

Overloads:

  • #each_triple {|subject, predicate, object| ... } ⇒ void

    This method returns an undefined value.

    Yields:

    • (subject, predicate, object) —

      each triple

    Yield Parameters:

    Yield Returns:

    • (void) —

      ignored

  • #each_triple ⇒ Enumerator

    Returns:

See Also:



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# File 'lib/rdf/reader.rb', line 328

def each_triple(&block)
  if block_given?
    begin
      loop { block.call(*read_triple) }
    rescue EOFError => e
      rewind rescue nil
    end
  end
  enum_for(:each_triple)
end

#prefix(name, uri) ⇒ RDF::URI #prefix(name) ⇒ RDF::URI Also known as: prefix!

Defines the given named URI prefix for this reader.

Examples:

Defining a URI prefix

reader.prefix :dc, RDF::URI('http://purl.org/dc/terms/')

Returning a URI prefix

reader.prefix(:dc)    #=> RDF::URI('http://purl.org/dc/terms/')

Overloads:

  • #prefix(name, uri) ⇒ RDF::URI

    Parameters:

    • name (Symbol, #to_s)
    • uri (RDF::URI, #to_s)
  • #prefix(name) ⇒ RDF::URI

    Parameters:

    • name (Symbol, #to_s)

Returns:



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# File 'lib/rdf/reader.rb', line 268

def prefix(name, uri = nil)
  name = name.to_s.empty? ? nil : (name.respond_to?(:to_sym) ? name.to_sym : name.to_s.to_sym)
  uri.nil? ? prefixes[name] : prefixes[name] = uri
end

#prefixes ⇒ Hash{Symbol => RDF::URI}

Returns the URI prefixes currently defined for this reader.

Examples:

reader.prefixes[:dc]  #=> RDF::URI('http://purl.org/dc/terms/')

Returns:

Since:

  • 0.3.0



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# File 'lib/rdf/reader.rb', line 232

def prefixes
  @options[:prefixes] ||= {}
end

#prefixes=(prefixes) ⇒ Hash{Symbol => RDF::URI}

Defines the given URI prefixes for this reader.

Examples:

reader.prefixes = {
  :dc => RDF::URI('http://purl.org/dc/terms/'),
}

Parameters:

Returns:

Since:

  • 0.3.0



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# File 'lib/rdf/reader.rb', line 247

def prefixes=(prefixes)
  @options[:prefixes] = prefixes
end

#rewind ⇒ void Also known as: rewind!

This method returns an undefined value.

Rewinds the input stream to the beginning of input.

See Also:

Since:

  • 0.2.3



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# File 'lib/rdf/reader.rb', line 345

def rewind
  @input.rewind
end

#to_sym ⇒ Symbol

Returns a symbol appropriate to use with RDF::Reader.for()

Returns:

  • (Symbol) 


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# File 'lib/rdf/reader.rb', line 158

def to_sym
  self.class.to_sym
end