Class: RDF::Repository

Inherits:
Object
  • Object
show all
Includes:
MonitorMixin, Parser
Defined in:
lib/lightrdf/repository.rb

Instance Method Summary collapse

Methods included from Parser

parse, #serialize, #to_ntriples

Constructor Details

#initialize(options = {}) ⇒ Repository

Returns a new instance of Repository.



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# File 'lib/lightrdf/repository.rb', line 6

def initialize options={}
  super()
  
  # Assigns the default value to the options.
  @options = {:host=>"http://localhost", :port=>8080, :repository=>"memory", :format=>:ntriples}.merge(options)
end

Instance Method Details

#contexts ⇒ Object

Gets the list of the sesame contexts



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# File 'lib/lightrdf/repository.rb', line 30

def contexts
  synchronize do
    # The URL to get the context list from sesame
    url = "#{repository_url(@options[:repository])}/contexts"

    # Asks for the context list and parses it
    Nokogiri::XML( RestClient.get(url, :content_type=>'application/sparql-results+xml') ).search(:uri).map(&:text)
  end
end

#data(*contexts) ⇒ Object

Extracts the data in sesame from the indicated repositories



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# File 'lib/lightrdf/repository.rb', line 14

def data *contexts
   synchronize do
     params = ("?" + contexts.flatten.map{|context| "context=%3C#{CGI::escape(context)}%3E"}*"&&" if !contexts.empty?)

     # Prepares the URL to request the data
     url = "#{repository_statements_url(@options[:repository])}#{params}"

     # Asks for the data
     ntriples = RestClient.get url, :content_type=>content_type

     # Builds the graph
     Parser.parse :rdf, ntriples
   end
end

#data=(*args) ⇒ Object

Adds data to sesame without removing the previous data



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# File 'lib/lightrdf/repository.rb', line 41

def data= *args
  synchronize do
    # Retrieve arguments
    graph, context = if args.first.is_a?(Array)
        [args.first.first, args.first.last]
      else
        [args.first, nil]
      end
    
    # Prepares the dir to connect with the repository
    url  = "#{repository_statements_url(@options[:repository])}"
    url += "?context=%3C#{CGI::escape(context)}%3E" if context
    data = graph.serialize :ntriples

    # Adds the data to Sesame
    RestClient.post url, data, :content_type=>content_type
  end
end

#query(string) ⇒ Object

Performs a query based on turtle syntax and assuming ?q as variable



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# File 'lib/lightrdf/repository.rb', line 61

def query string
  query = ""
  RDF::ID.ns.each do |prefix, uri|
    query += "PREFIX #{prefix}: <#{uri}>\n"
  end
  query += "SELECT ?q\n"
  query += "WHERE {#{string}}"
  
  results = sparql(query)
  results.children.first.children[3].children.select { |result| !result.text? }.map do |result|
    node = result.children[1].children[1]
    case node.name.to_sym
    when :uri then
      Node(node.content)
    when :bnode then
      Node("_:#{node.content}")
    when :literal then
      node.content
    end        
  end
end

#sparql(query) ⇒ Object

Performs a SPARQL query



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# File 'lib/lightrdf/repository.rb', line 84

def sparql query
  synchronize do
    url = "#{repository_url(@options[:repository])}?query=#{CGI::escape(query)}"
    Nokogiri::XML( RestClient.get(url, :content_type=>'application/sparql-results+xml') )
  end
end