Class: RDF::RSS10::Reader

Inherits:
RDF::Reader
  • Object
show all
Defined in:
lib/sasquatch/rss10/reader.rb

Instance Method Summary collapse

Constructor Details

#initialize(input = $stdin, options = {}, &block) ⇒ Reader

copied indiscriminately from gkellogg’s rdf/xml parser



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# File 'lib/sasquatch/rss10/reader.rb', line 6

def initialize(input = $stdin, options = {}, &block)
  super do
    
    @base_uri = uri(options[:base_uri]) if options[:base_uri]
        
    @doc = case input
    when Nokogiri::XML::Document then input
    else Nokogiri::XML.parse(input, @base_uri.to_s)
    end
    
    raise RDF::ReaderError, "Synax errors:\n#{@doc.errors}" if !@doc.errors.empty? && validate?
    raise RDF::ReaderError, "Empty document" if (@doc.nil? || @doc.root.nil?) && validate?

    block.call(self) if block_given?
  end
end

Instance Method Details

#all_text_nodes?(nodes) ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/sasquatch/rss10/reader.rb', line 135

def all_text_nodes?(nodes)
  all_text = true
  nodes.each {|n| all_text = false unless n.is_a?(Nokogiri::XML::Text)}
  all_text
end

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

This method returns an undefined value.

Iterates the given block for each RDF statement in the input.

Yields:

  • (statement)

Yield Parameters:



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# File 'lib/sasquatch/rss10/reader.rb', line 28

def each_statement(&block)
  # Block called from add_statement
  @callback = block

  root = @doc.root


  rdf_nodes = root.xpath("/rdf:RDF", "rdf" => RDF.to_uri.to_s)
  statements = []
  rdf_nodes.each do |node|


    root.xpath("//rss:channel", "rss"=>RDF::RSS.to_s).each do |channel|
      if channel.attribute('about')
        channel_uri = RDF::URI.intern(channel.attribute('about').value)
      else
        channel_uri = RDF::Node.new
      end
      statements << RDF::Statement.new(channel_uri, RDF.type, RDF::RSS.channel)
      channel.children.each do |elem|
        unless elem.name == 'items'
          if elem.children.length == 1 && elem.children.first.is_a?(Nokogiri::XML::Text)
            statements << RDF::Statement.new(channel_uri, RDF::URI.intern(elem.namespace.href + elem.name), literal(elem.children.first))
          elsif elem.attribute('resource')
            statements << RDF::Statement.new(channel_uri, RDF::URI.intern(elem.namespace.href + elem.name), RDF::URI.intern(elem.attribute('resource').value))
          end
        else
          stmt = RDF::Statement.new(:subject=>channel_uri, :predicate=>RDF::URI.intern(elem.namespace.href + elem.name))
          elem.children.each do |list|
            if list.attribute('about')
              list_uri = RDF::URI.intern(list.attribute('about').value)
            else
              list_uri = RDF::Node.new
            end

            stmt.object = list_uri
            statements << stmt
            list_type = RDF::URI.intern(list.namespace.href + list.name)
            unless list_type == RDF.Description
              statements << RDF::Statement.new(:subject=>list_uri, :predicate=>RDF.type, :object=>list_type)
            end
            list.children.each do |li|
              stmt = RDF::Statement.new(:subject=>list_uri, :predicate=>RDF::URI.intern(li.namespace.href + li.name))
              if li.attribute('resource')
                stmt.object = RDF::URI.intern(li.attribute('resource').value)
              elsif li.children.length == 1 && li.children.first.is_a?(Nokogiri::XML::Text)
                stmt.object = literal(li.children.first)
              end
              statements << stmt if stmt.object
            end
          end
        end
      end
    end
    root.xpath("/rdf:RDF/rss:item", "rdf"=>RDF.to_uri.to_s, "rss"=>RDF::RSS.to_s).each do |item|
      if item.attribute('about')
        item_uri = RDF::URI.intern(item.attribute('about').value)
      else
        item_uri = RDF::Node.new
      end
      statements.concat statements_from_element(item, item_uri)
    end


  end
  statements.each do |stmt |
    yield stmt
  end   
  statements.to_enum    
end

#has_child_elements?(elem) ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/sasquatch/rss10/reader.rb', line 141

def has_child_elements?(elem)
  children = false
  elem.each {|e| children = true if e.is_a?(Nokogiri::XML::Element)}
  children
end

#literal(txt) ⇒ Object 



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# File 'lib/sasquatch/rss10/reader.rb', line 147

def literal(txt)
  options = {}
  if txt.attribute('lang')
    options[:language] = txt.attribute('lang').value.to_sym
  end
  if txt.attribute_with_ns('datatype', RDF.to_uri.to_s)
    options[:datatype] = RDF::URI.intern(txt.attribute_with_ns('datatype', RDF.to_uri.to_s).value)
  end
  RDF::Literal.new(txt.inner_text, options)       
end

#parse_children(elem, stmt) ⇒ Object 



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# File 'lib/sasquatch/rss10/reader.rb', line 158

def parse_children(elem, stmt)
  old_stmt = nil
  statements = []
  if elem.attribute_with_ns("about", RDF.to_uri.to_s)
    old_stmt = stmt
    stmt = RDF::Statement.new(:subject=>elem.attribute_with_ns("about", RDF.to_uri.to_s).value)
    type_object = RDF::URI.intern(elem.namespace.href+elem.name)
    unless type_object == RDF.Description || type_object == RDF::RSS.item
      stmt.predicate = RDF.type
      stmt.object = type_object
      statements << stmt
      stmt = RDF::Statement.new
      stmt.subject = RDF::URI.intern(elem.attribute_with_ns('about', RDF.to_uri.to_s).value)
    end
  end         
  elem.children.each do |el|
    next if el.is_a?(Nokogiri::XML::Text)
    if el.attribute_with_ns('resource', RDF.to_uri.to_s) || el.attribute('resource')
      if el.attribute_with_ns('resource', RDF.to_uri.to_s)
        stmt.object = RDF::URI.intern(el.attribute_with_ns('resource', RDF.to_uri.to_s).value)
      else
        stmt.object = RDF::URI.intern(el.attribute('resource').value)
      end
      stmt.predicate = RDF::URI.intern(el.namespace.href+el.name)
      statements << stmt.dup
      stmt = RDF::Statement.new(:subject=>stmt.subject)
    elsif el.children.length == 1 && el.children.first.is_a?(Nokogiri::XML::Text)
      stmt.predicate = RDF::URI.intern(el.namespace.href+el.name)
      options = {}
      txt = el.children.first
      if txt.attribute('lang')
        options[:language] = txt.attribute('lang').value.to_sym
      end
      if txt.attribute_with_ns('datatype', RDF.to_uri.to_s)
        options[:datatype] = RDF::URI.intern(txt.attribute_with_ns('datatype', RDF.to_uri.to_s).value)
      end
      stmt.object = RDF::Literal.new(txt.inner_text, options)
      statements << stmt.dup
      stmt = RDF::Statement.new(:subject=>stmt.subject)
    else
      stmt_found = false
      el.children.each do |child|
        next unless child.is_a?(Nokogiri::XML::Element)
        stmt.predicate = RDF::URI.intern(el.namespace.href+el.name)
        if child.attribute_with_ns("about", RDF.to_uri.to_s)
          stmt.object = RDF::URI.intern(child.attribute_with_ns("about", RDF.to_uri.to_s).value)
          statements << stmt.dup
          stmt = RDF::Statement.new(:subject=>stmt.subject)
          stmt_found = true
        else
          stmt.object = RDF::Node.new
          statements << stmt.dup
          stmt = RDF::Statement.new(:subject=>stmt.subject)
          stmt_found = true
        end               
      end
      puts "#{el.name}: #{el.inspect}" unless stmt_found
    end
        
    #puts "#{el.name}: #{el.class.name}"
    statements.concat parse_children(el, stmt) unless el.children.empty?
  end
  if old_stmt
    stmt = old_stmt
  end
  statements
end

#statements_from_element(elem, resource) ⇒ Object 



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# File 'lib/sasquatch/rss10/reader.rb', line 99

def statements_from_element(elem, resource)
  child_elements = {}
  statements = []
  elem.children.each do |el|
    if el.attribute_with_ns('resource', RDF.to_uri.to_s)
      statements << RDF::Statement.new(:subject=>resource, :predicate=>RDF::URI.intern(el.namespace.href+el.name), :object=>RDF::URI.intern(el.attribute_with_ns('resource', RDF.to_uri.to_s).value))
    elsif all_text_nodes?(el.children)
      statements << RDF::Statement.new(:subject=>resource, :predicate=>RDF::URI.intern(el.namespace.href+el.name),:object=>literal(el.children.first))
    else
      el.children.each do |e|
        if e.attribute_with_ns('about', RDF.to_uri.to_s)
          c = RDF::URI.intern(e.attribute_with_ns('about', RDF.to_uri.to_s).value)
          statements << RDF::Statement.new(:subject=>resource, :predicate=>RDF::URI.intern(el.namespace.href+el.name), :object=>c)  
          child_elements[c] = e
          e_type = RDF::URI.intern(e.namespace.href + e.name)
          unless e_type == RDF.Description || RDF::RSS.item
            statements << RDF::Statement.new(:subject=>c, :predicate=>RDF.type, :object=>e_type)
          end
        elsif has_child_elements?(e)   
          c = RDF::Node.new         
          statements << RDF::Statement.new(:subject=>resource, :predicate=>RDF::URI.intern(el.namespace.href+el.name), :object=>c)  
          child_elements[c] = e
          e_type = RDF::URI.intern(e.namespace.href + e.name)
          unless e_type == RDF.Description || RDF::RSS.item
            statements << RDF::Statement.new(:subject=>c, :predicate=>RDF.type, :object=>e_type)
          end
        end               
      end
    end
  end
  child_elements.each_pair do |r,e|
    statements.concat statements_from_element(e, r)
  end
  statements
end