Class: RdfContext::N3Parser

Inherits:
Parser
  • Object
show all
Defined in:
lib/rdf_context/n3parser.rb

Constant Summary

N3_KEYWORDS =
%w(a

Instance Attribute Summary

Attributes inherited from Parser

#debug, #doc, #graph, #processor_graph, #uri

Instance Method Summary (collapse)

Methods inherited from Parser

#add_debug, #add_error, #add_info, #add_processor_message, #add_triple, #add_warning, #detect_format, #initialize, n3_parser, #node_path, parse, rdfa_parser, rdfxml_parser

Constructor Details

This class inherits a constructor from RdfContext::Parser

Instance Method Details

- (Object) build_uri(expression) (protected)



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# File 'lib/rdf_context/n3parser.rb', line 327

def build_uri(expression)
  prefix = expression.respond_to?(:nprefix) ? expression.nprefix.text_value.to_s : ""
  localname = expression.localname.text_value if expression.respond_to?(:localname)
  localname ||= (expression.respond_to?(:text_value) ? expression.text_value : expression).to_s.sub(/^:/, "")
  localname = nil if localname.empty? # In N3/Turtle "_:" is not named

  if expression.respond_to?(:info)
    add_debug(*expression.info("build_uri(#{prefix.inspect}, #{localname.inspect})"))
  else
    add_debug("", "build_uri(#{prefix.inspect}, #{localname.inspect})")
  end

  uri = if @graph.nsbinding[prefix]
    @graph.nsbinding[prefix] + localname.to_s
  elsif prefix == '_'
    BNode.new(localname, @named_bnodes)
  elsif prefix == "rdf"
    # A special case
    RDF_NS + localname.to_s
  elsif prefix == "xsd"
    # A special case
    XSD_NS + localname.to_s
  else
    @default_ns ||= Namespace.new("#{@uri}#", "")
    @default_ns + localname.to_s
  end
  add_debug(*expression.info("build_uri: #{uri.inspect}")) if expression.respond_to?(:info)
  uri
end

- (Object) keyword_check(kw) (protected)

Is this an allowable keyword?



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# File 'lib/rdf_context/n3parser.rb', line 358

def keyword_check(kw)
  unless (@keywords || %w(a is of has)).include?(kw)
    raise ParserException, "unqualified keyword '#{kw}' used without @keyword directive" if @strict
  end
end

- (Object) namespace(uri, prefix) (protected)



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# File 'lib/rdf_context/n3parser.rb', line 49

def namespace(uri, prefix)
  add_debug("namesspace", "'#{prefix}' <#{uri}>")
  uri = @default_ns.uri if uri == '#'
  @graph.bind(Namespace.new(uri, prefix))
  add_debug("namesspace", "ns = #{@graph.nsbinding.inspect}")
end

- (Graph) parse(stream, uri = nil, options = {}, &block)

Parse N3 document from a string or input stream to closure or graph.

If the parser is called with a block, triples are passed to the block rather than added to the graph.

Options Hash (options):

  • :graph (Graph) — default: Graph.new

    Graph to parse into, otherwise a new Graph instance is created

  • :debug (Array) — default: nil

    Array to place debug messages

  • :strict (Boolean) — default: false

    Raise Error if true, continue with lax parsing, otherwise

Raises:

  • RdfException or subclass

Author:

  • Patrick Sinclair (metade)

  • Gregg Kellogg



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# File 'lib/rdf_context/n3parser.rb', line 25

def parse(stream, uri = nil, options = {}, &block) # :yields: triple
  super

  @callback = block
  parser = N3GrammerParser.new

  @doc = stream.respond_to?(:read) ? (stream.rewind; stream.read) : stream
  @default_ns = Namespace.new("#{uri}#", "")  if uri
  add_debug("@default_ns", "#{@default_ns.inspect}")

  @graph.allow_n3 = true
  document = parser.parse(@doc)
  unless document
    puts parser.inspect if ::RdfContext::debug?
    reason = parser.failure_reason
    raise ParserException.new(reason)
  end
  
  process_statements(document)
  @graph
end

- (Object) process_anonnode(anonnode) (protected)



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# File 'lib/rdf_context/n3parser.rb', line 118

def process_anonnode(anonnode)
  add_debug(*anonnode.info("process_anonnode"))
  bnode = BNode.new
  
  if anonnode.respond_to?(:property_list)
    properties = process_properties(anonnode.property_list)
    properties.each do |p|
      predicate = process_verb(p.verb)
      add_debug(*p.info("anonnode[#{predicate}]"))
      objects = process_objects(p.object_list)
      objects.each { |object| add_triple("anonnode", bnode, predicate, object) }
    end
  elsif anonnode.respond_to?(:path_list)
    objects = process_objects(anonnode.path_list)
    last = objects.pop
    first_bnode = bnode
    objects.each do |object|
      add_triple("anonnode", first_bnode, RDF_NS.first, object)
      rest_bnode = BNode.new
      add_triple("anonnode", first_bnode, RDF_NS.rest, rest_bnode)
      first_bnode = rest_bnode
    end
    if last
      add_triple("anonnode", first_bnode, RDF_NS.first, last)
      add_triple("anonnode", first_bnode, RDF_NS.rest, RDF_NS.nil)
    else
      bnode = RDF_NS.nil
    end
  end
  bnode
end

- (Object) process_barename_csl(list) (protected)



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# File 'lib/rdf_context/n3parser.rb', line 111

def process_barename_csl(list)
  #add_debug(*list.info("process_barename_csl(list)"))
  res = [list.barename.text_value] if list.respond_to?(:barename)
  rest = process_barename_csl(list.barename_csl_tail) if list.respond_to?(:barename_csl_tail)
  rest ? res + rest : res
end

- (Object) process_expression(expression) (protected)



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# File 'lib/rdf_context/n3parser.rb', line 180

def process_expression(expression)
  if expression.respond_to?(:pathitem) && expression.respond_to?(:expression)
    add_debug(*expression.info("process_expression(pathitem && expression)"))
    process_path(expression)  # Returns last object in chain
  elsif expression.respond_to?(:uri)
    add_debug(*expression.info("process_expression(uri)"))
    process_uri(expression.uri)
  elsif expression.respond_to?(:localname)
    add_debug(*expression.info("process_expression(localname)"))
    build_uri(expression)
  elsif expression.respond_to?(:anonnode)
    add_debug(*expression.info("process_expression(anonnode)"))
    process_anonnode(expression)
  elsif expression.respond_to?(:literal)
    add_debug(*expression.info("process_expression(literal)"))
    process_literal(expression)
  elsif expression.respond_to?(:numericliteral)
    add_debug(*expression.info("process_expression(numericliteral)"))
    process_numeric_literal(expression)
  elsif expression.respond_to?(:boolean)
    add_debug(*expression.info("process_expression(boolean)"))
    barename = expression.text_value.to_s
    if @keywords && !@keywords.include?(barename)
      build_uri(barename)
    else
      Literal.typed(barename.delete("@"), XSD_NS.boolean)
    end
  elsif expression.respond_to?(:barename)
    add_debug(*expression.info("process_expression(barename)"))
    barename = expression.text_value.to_s
    
    # Should only happen if @keywords is defined, and text_value is not a defined keyword
    case barename
    when "true"   then Literal.typed("true", XSD_NS.boolean)
    when "false"  then Literal.typed("false", XSD_NS.boolean)
    else
      # create URI using barename, unless it's in defined set, in which case it's an error
      raise ParserException, %Q(Keyword "#{barename}" used as expression) if @keywords && @keywords.include?(barename)
      build_uri(barename)
    end
  else
    add_debug(*expression.info("process_expression(else)"))
    build_uri(expression)
  end
end

- (Object) process_literal(object) (protected)

Raises:



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# File 'lib/rdf_context/n3parser.rb', line 300

def process_literal(object)
  add_debug(*object.info("process_literal"))
  encoding, language = nil, nil
  string, type = object.elements

  unless type.elements.nil?
    #puts type.elements.inspect
    if (type.elements[0].text_value=='@')
      language = type.elements[1].text_value
    else
      encoding = process_expression(type.elements[1])
    end
  end

  # Evaluate text_value to remove redundant escapes
  #puts string.elements[1].text_value.dump
  lit = Literal.n3_encoded(string.elements[1].text_value, language, encoding)
  raise ParserException, %(Typed literal has an invalid lexical value: #{encoding.to_n3} "#{lit.contents}") if @strict && !lit.valid?
  lit
end

- (Object) process_numeric_literal(object) (protected)



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# File 'lib/rdf_context/n3parser.rb', line 321

def process_numeric_literal(object)
  add_debug(*object.info("process_numeric_literal"))

  Literal.typed(object.text_value, XSD_NS.send(object.numericliteral))
end

- (Object) process_objects(objects) (protected)



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# File 'lib/rdf_context/n3parser.rb', line 283

def process_objects(objects)
  add_debug(*objects.info("process_objects"))
  result = []
  if objects.respond_to?(:object)
    result << process_expression(objects.object)
  elsif objects.respond_to?(:pathitem)
    result << process_expression(objects)
  elsif objects.respond_to?(:expression)
    result << process_expression(objects.expression)
    result << process_objects(objects.path_list) if objects.respond_to?(:path_list)
  elsif !objects.text_value.empty? || objects.respond_to?(:nprefix)
    result << process_expression(objects)
  end
  result << process_objects(objects.object_list) if objects.respond_to?(:object_list)
  result.flatten
end

- (Object) process_path(path) (protected)

Process a path, such as:

:a.:b means [is :b of :a]
:a!:b means [is :b of :a]
:a^:b means [:b :a]

Elements may be strug together, with the last element the verb applied to the previous expression:

:a.:b.:c means [is :c of [ is :b of :a]]
:a!:b^:c meands [:c [ is :b of :a]]


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# File 'lib/rdf_context/n3parser.rb', line 234

def process_path(path)
  add_debug(*path.info("process_path"))

  object = process_expression(path.pathitem)
  
  # Create a list of direction/predicate pairs
  path_list = process_path_list(path.expression, path.respond_to?(:reverse))
  #puts path_list.inspect
  # Now we should have the following
  # [
  #   [:forward, b]
  #   [:forward, c]
  # ]
  path_list.each do |p|
    reverse, pred = p
    bnode = BNode.new
    if reverse
      add_triple("path(#{reverse})", bnode, pred, object)
    else
      add_triple("path(#{reverse})", object, pred, bnode)
    end
    object = bnode
  end
  object
end

- (Object) process_path_list(path, reverse) (protected)

Returns array of [:forward/:reverse, element] pairs



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# File 'lib/rdf_context/n3parser.rb', line 261

def process_path_list(path, reverse)
  add_debug(*path.info("process_path_list(#{reverse})"))
  if path.respond_to?(:pathitem)
    [[reverse, process_expression(path.pathitem)]] + process_path_list(path.expression, path.respond_to?(:reverse))
  else
    [[reverse, process_expression(path)]]
  end
end

- (Object) process_properties(properties) (protected)



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# File 'lib/rdf_context/n3parser.rb', line 275

def process_properties(properties)
  add_debug(*properties.info("process_properties"))
  result = []
  result << properties if properties.respond_to?(:verb)
  result << process_properties(properties.property_list) if properties.respond_to?(:property_list)
  result.flatten
end

- (Object) process_statements(document) (protected)



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# File 'lib/rdf_context/n3parser.rb', line 56

def process_statements(document)
  document.elements.find_all do |e|
    s = e.elements.first
    add_debug(*s.info("process_statements"))
    
    if s.respond_to?(:subject)
      subject = process_expression(s.subject)
      add_debug(*s.info("process_statements(#{subject})"))
      properties = process_properties(s.property_list)
      properties.each do |p|
        predicate = process_verb(p.verb)
        add_debug(*p.info("process_statements(#{subject}, #{predicate})"))
        raise ParserException, %Q(Illegal statment: "#{predicate}" missing object) unless p.respond_to?(:object_list)
        objects = process_objects(p.object_list)
        objects.each do |object|
          if p.verb.respond_to?(:invert)
            add_triple("statement", object, predicate, subject)
          else
            add_triple("statement", subject, predicate, object)
          end
        end
      end
    elsif s.respond_to?(:anonnode)
      process_anonnode(s)
    elsif s.respond_to?(:pathitem)
      process_path(s)
    elsif s.respond_to?(:declaration)
      if s.respond_to?(:nprefix)
        add_debug(*s.info("process_statements(namespace)"))
        keyword_check("prefix") if s.text_value.index("prefix") == 0
        uri = process_uri(s.explicituri.uri)
        namespace(uri, s.nprefix.text_value)
      elsif s.respond_to?(:base)
        add_debug(*s.info("process_statements(base)"))
        keyword_check("base") if s.text_value.index("base") == 0
        # Base, set or update document URI
        uri = s.explicituri.uri.text_value
        @default_ns = Namespace.new(process_uri(uri), "")  # Don't normalize
        add_debug("@default_ns", "#{@default_ns.inspect}")
        @uri = process_uri(uri)
        add_debug("@base", "#{@uri}")
        @uri
      elsif s.respond_to?(:keywords)
        add_debug(*s.info("process_statements(keywords)"))
        keyword_check("keywords") if s.text_value.index("keywords") == 0
        @keywords = process_barename_csl(s.barename_csl) ||[]
        add_debug("@keywords", @keywords.inspect)
        if (@keywords & N3_KEYWORDS) != @keywords
          raise ParserException, "undefined keywords used: #{(@keywords - N3_KEYWORDS).to_sentence}" if @strict
        end
      end
    end
  end
end

- (Object) process_uri(uri) (protected)



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# File 'lib/rdf_context/n3parser.rb', line 270

def process_uri(uri)
  uri = uri.text_value if uri.respond_to?(:text_value)
  URIRef.intern(uri.to_s.rdf_unescape, @uri, :normalize => false)
end

- (Object) process_verb(verb) (protected)



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# File 'lib/rdf_context/n3parser.rb', line 150

def process_verb(verb)
  add_debug(*verb.info("process_verb"))
  case verb.text_value
  when "a"
    # If "a" is a keyword, then it's RDF_TYPE, otherwise it's expanded from the default namespace
    if @keywords.nil? || @keywords.include?("a")
      RDF_TYPE
    else
      build_uri("a")
    end
  when "@a"           then RDF_TYPE
  when "="            then OWL_NS.sameAs
  when "=>"           then LOG_NS.implies
  when "<="           then LOG_NS.implies
  when /^(@?is)\s+.*\s+(@?of)$/
    keyword_check("is") if $1 == "is"
    keyword_check("of") if $2 == "of"
    process_expression(verb.prop)
  when /^has\s+/
    keyword_check("has")
    process_expression(verb.prop)
  else
    if verb.respond_to?(:prop)
      process_expression(verb.prop)
    else
      process_expression(verb)
    end
  end
end