require 'spreadsheet'
require 'yajl'

module OpenTox

  # Serialzer for various oputput formats
  module Serializer

    # OWL-DL Serializer, modelled according to to http://n2.talis.com/wiki/RDF_JSON_Specification
    class Owl

      attr_accessor :object

      def initialize

        @object = {
          # this should come from opentox.owl
          OT.Compound => { RDF["type"] => [{ "type" => "uri", "value" => OWL['Class'] }] } ,
          OT.Feature => { RDF["type"] => [{ "type" => "uri", "value" => OWL['Class'] }] } ,
          OT.Model => { RDF["type"] => [{ "type" => "uri", "value" => OWL['Class'] }] } ,
          OT.NominalFeature => { RDF["type"] => [{ "type" => "uri", "value" => OWL['Class'] }] } ,
          OT.NumericFeature => { RDF["type"] => [{ "type" => "uri", "value" => OWL['Class'] }] } ,
          OT.StringFeature => { RDF["type"] => [{ "type" => "uri", "value" => OWL['Class'] }] } ,
          OT.Dataset => { RDF["type"] => [{ "type" => "uri", "value" => OWL['Class'] }] } ,
          OT.DataEntry => { RDF["type"] => [{ "type" => "uri", "value" => OWL['Class'] }] } ,
          OT.FeatureValue => { RDF["type"] => [{ "type" => "uri", "value" => OWL['Class'] }] } ,
          OT.Algorithm => { RDF["type"] => [{ "type" => "uri", "value" => OWL['Class'] }] } ,
          OT.Parameter => { RDF["type"] => [{ "type" => "uri", "value" => OWL['Class'] }] } ,
          OT.Task => { RDF["type"] => [{ "type" => "uri", "value" => OWL['Class'] }] } ,
          OTA.PatternMiningSupervised => { RDF["type"] => [{ "type" => "uri", "value" => OWL['Class'] }] } ,
          OTA.ClassificationLazySingleTarget => { RDF["type"] => [{ "type" => "uri", "value" => OWL['Class'] }] } ,
          OTA.RegressionLazySingleTarget => { RDF["type"] => [{ "type" => "uri", "value" => OWL['Class'] }] } ,

          #classes for validation
          OT.Validation => { RDF["type"] => [{ "type" => "uri", "value" => OWL['Class'] }] } ,
          OT.ClassificationStatistics => { RDF["type"] => [{ "type" => "uri", "value" => OWL['Class'] }] } ,
          OT.ConfusionMatrix => { RDF["type"] => [{ "type" => "uri", "value" => OWL['Class'] }] } ,
          OT.ConfusionMatrixCell => { RDF["type"] => [{ "type" => "uri", "value" => OWL['Class'] }] } ,
          OT.ClassValueStatistics => { RDF["type"] => [{ "type" => "uri", "value" => OWL['Class'] }] } ,
          OT.RegressionStatistics => { RDF["type"] => [{ "type" => "uri", "value" => OWL['Class'] }] } ,
          OT.Crossvalidation => { RDF["type"] => [{ "type" => "uri", "value" => OWL['Class'] }] } ,
          OT.CrossvalidationInfo => { RDF["type"] => [{ "type" => "uri", "value" => OWL['Class'] }] } ,
          OT.ErrorReport => { RDF["type"] => [{ "type" => "uri", "value" => OWL['Class'] }] } ,

          OT.compound => { RDF["type"] => [{ "type" => "uri", "value" => OWL.ObjectProperty }] } ,
          OT.feature => { RDF["type"] => [{ "type" => "uri", "value" => OWL.ObjectProperty }] } ,
          OT.dataEntry => { RDF["type"] => [{ "type" => "uri", "value" => OWL.ObjectProperty }] } ,
          OT.values => { RDF["type"] => [{ "type" => "uri", "value" => OWL.ObjectProperty }] } ,
          OT.algorithm => { RDF["type"] => [{ "type" => "uri", "value" => OWL.ObjectProperty }] } ,
          OT.parameters => { RDF["type"] => [{ "type" => "uri", "value" => OWL.ObjectProperty }] } ,
          OT.featureDataset => { RDF["type"] => [{ "type" => "uri", "value" => OWL.ObjectProperty }] } ,
          OT.dependentVariables => { RDF["type"] => [{ "type" => "uri", "value" => OWL.ObjectProperty }] } ,
          OT.predictedVariables => { RDF["type"] => [{ "type" => "uri", "value" => OWL.ObjectProperty }] } ,
          OT.paramValue => { RDF["type"] => [{ "type" => "uri", "value" => OWL.ObjectProperty }] } ,

          #object props for validation#           
          OT.model => { RDF["type"] => [{ "type" => "uri", "value" => OWL.ObjectProperty }] } ,
          OT.trainingDataset => { RDF["type"] => [{ "type" => "uri", "value" => OWL.ObjectProperty }] } ,
          OT.predictionFeature => { RDF["type"] => [{ "type" => "uri", "value" => OWL.ObjectProperty }] } ,
          OT.predictionDataset => { RDF["type"] => [{ "type" => "uri", "value" => OWL.ObjectProperty }] } ,
          OT.crossvalidation => { RDF["type"] => [{ "type" => "uri", "value" => OWL.ObjectProperty }] } ,
          OT.testTargetDataset => { RDF["type"] => [{ "type" => "uri", "value" => OWL.ObjectProperty }] } ,
          OT.testDataset => { RDF["type"] => [{ "type" => "uri", "value" => OWL.ObjectProperty }] } ,
          OT.classificationStatistics => { RDF["type"] => [{ "type" => "uri", "value" => OWL.ObjectProperty }] } ,
          OT.confusionMatrix => { RDF["type"] => [{ "type" => "uri", "value" => OWL.ObjectProperty }] } ,
          OT.confusionMatrixCell => { RDF["type"] => [{ "type" => "uri", "value" => OWL.ObjectProperty }] } ,
          OT.classValueStatistics => { RDF["type"] => [{ "type" => "uri", "value" => OWL.ObjectProperty }] } ,
          OT.regressionStatistics => { RDF["type"] => [{ "type" => "uri", "value" => OWL.ObjectProperty }] } ,
          OT.validation => { RDF["type"] => [{ "type" => "uri", "value" => OWL.ObjectProperty }] } ,
          OT.crossvalidationInfo => { RDF["type"] => [{ "type" => "uri", "value" => OWL.ObjectProperty }] } ,
          OT.dataset => { RDF["type"] => [{ "type" => "uri", "value" => OWL.ObjectProperty }] } ,

          DC.title => { RDF["type"] => [{ "type" => "uri", "value" => OWL.AnnotationProperty }] } ,
          DC.identifier => { RDF["type"] => [{ "type" => "uri", "value" => OWL.AnnotationProperty }] } ,
          DC.contributor => { RDF["type"] => [{ "type" => "uri", "value" => OWL.AnnotationProperty }] } ,
          DC.creator => { RDF["type"] => [{ "type" => "uri", "value" => OWL.AnnotationProperty }] } ,
          DC.description => { RDF["type"] => [{ "type" => "uri", "value" => OWL.AnnotationProperty }] } ,
          DC.date => { RDF["type"] => [{ "type" => "uri", "value" => OWL.AnnotationProperty }] } ,
          #OT.isA => { RDF["type"] => [{ "type" => "uri", "value" => OWL.AnnotationProperty }] } ,
          OT.Warnings => { RDF["type"] => [{ "type" => "uri", "value" => OWL.AnnotationProperty }] } ,
          XSD.anyURI => { RDF["type"] => [{ "type" => "uri", "value" => OWL.AnnotationProperty }] } ,
          OT.hasStatus => { RDF["type"] => [{ "type" => "uri", "value" => OWL.AnnotationProperty }] } ,
          OT.resultURI => { RDF["type"] => [{ "type" => "uri", "value" => OWL.AnnotationProperty }] } ,
          OT.percentageCompleted => { RDF["type"] => [{ "type" => "uri", "value" => OWL.AnnotationProperty }] } ,
          OT.acceptValue => { RDF["type"] => [{ "type" => "uri", "value" => OWL.AnnotationProperty }] } ,

          # annotation props for validation        
          OT.numUnpredicted => { RDF["type"] => [{ "type" => "uri", "value" => OWL.AnnotationProperty }] } ,
          OT.crossvalidationFold => { RDF["type"] => [{ "type" => "uri", "value" => OWL.AnnotationProperty }] } ,
          OT.numInstances => { RDF["type"] => [{ "type" => "uri", "value" => OWL.AnnotationProperty }] } ,
          OT.numWithoutClass => { RDF["type"] => [{ "type" => "uri", "value" => OWL.AnnotationProperty }] } ,
          OT.percentWithoutClass => { RDF["type"] => [{ "type" => "uri", "value" => OWL.AnnotationProperty }] } ,
          OT.percentUnpredicted => { RDF["type"] => [{ "type" => "uri", "value" => OWL.AnnotationProperty }] } ,
          OT.confusionMatrixActual => { RDF["type"] => [{ "type" => "uri", "value" => OWL.AnnotationProperty }] } ,
          OT.confusionMatrixPredicted => { RDF["type"] => [{ "type" => "uri", "value" => OWL.AnnotationProperty }] } ,
          OT.confusionMatrixValue => { RDF["type"] => [{ "type" => "uri", "value" => OWL.AnnotationProperty }] } ,
          OT.numIncorrect => { RDF["type"] => [{ "type" => "uri", "value" => OWL.AnnotationProperty }] } ,
          OT.percentCorrect => { RDF["type"] => [{ "type" => "uri", "value" => OWL.AnnotationProperty }] } ,
          OT.numCorrect => { RDF["type"] => [{ "type" => "uri", "value" => OWL.AnnotationProperty }] } ,
          OT.accuracy => { RDF["type"] => [{ "type" => "uri", "value" => OWL.AnnotationProperty }] } ,
          OT.trueNegativeRate => { RDF["type"] => [{ "type" => "uri", "value" => OWL.AnnotationProperty }] } ,
          OT.truePositiveRate => { RDF["type"] => [{ "type" => "uri", "value" => OWL.AnnotationProperty }] } ,
          OT.falseNegativeRate => { RDF["type"] => [{ "type" => "uri", "value" => OWL.AnnotationProperty }] } ,
          OT.falsePositiveRate => { RDF["type"] => [{ "type" => "uri", "value" => OWL.AnnotationProperty }] } ,
          OT.numTrueNegatives => { RDF["type"] => [{ "type" => "uri", "value" => OWL.AnnotationProperty }] } ,
          OT.numTruePositives => { RDF["type"] => [{ "type" => "uri", "value" => OWL.AnnotationProperty }] } ,
          OT.numFalseNegatives => { RDF["type"] => [{ "type" => "uri", "value" => OWL.AnnotationProperty }] } ,
          OT.numFalsePositives => { RDF["type"] => [{ "type" => "uri", "value" => OWL.AnnotationProperty }] } ,
          OT.classValue => { RDF["type"] => [{ "type" => "uri", "value" => OWL.AnnotationProperty }] } ,
          OT.precision => { RDF["type"] => [{ "type" => "uri", "value" => OWL.AnnotationProperty }] } ,
          OT.areaUnderRoc => { RDF["type"] => [{ "type" => "uri", "value" => OWL.AnnotationProperty }] } ,
          OT.weightedAreaUnderRoc => { RDF["type"] => [{ "type" => "uri", "value" => OWL.AnnotationProperty }] } ,
          OT.weightedAccuracy => { RDF["type"] => [{ "type" => "uri", "value" => OWL.AnnotationProperty }] } ,
          OT.fMeasure => { RDF["type"] => [{ "type" => "uri", "value" => OWL.AnnotationProperty }] } ,
          OT.percentIncorrect => { RDF["type"] => [{ "type" => "uri", "value" => OWL.AnnotationProperty }] } ,
          OT.validationType => { RDF["type"] => [{ "type" => "uri", "value" => OWL.AnnotationProperty }] } ,
          OT.realRuntime => { RDF["type"] => [{ "type" => "uri", "value" => OWL.AnnotationProperty }] } ,
          OT.sampleCorrelationCoefficient => { RDF["type"] => [{ "type" => "uri", "value" => OWL.AnnotationProperty }] } ,
          OT.targetVarianceActual => { RDF["type"] => [{ "type" => "uri", "value" => OWL.AnnotationProperty }] } ,
          OT.targetVariancePredicted => { RDF["type"] => [{ "type" => "uri", "value" => OWL.AnnotationProperty }] } ,
          OT.meanAbsoluteError => { RDF["type"] => [{ "type" => "uri", "value" => OWL.AnnotationProperty }] } ,
          OT.sumSquaredError => { RDF["type"] => [{ "type" => "uri", "value" => OWL.AnnotationProperty }] } ,
          OT.rootMeanSquaredError => { RDF["type"] => [{ "type" => "uri", "value" => OWL.AnnotationProperty }] } ,
          OT.rSquare => { RDF["type"] => [{ "type" => "uri", "value" => OWL.AnnotationProperty }] } ,
          OT.stratified => { RDF["type"] => [{ "type" => "uri", "value" => OWL.AnnotationProperty }] } ,
          OT.numFolds => { RDF["type"] => [{ "type" => "uri", "value" => OWL.AnnotationProperty }] } ,
          OT.randomSeed => { RDF["type"] => [{ "type" => "uri", "value" => OWL.AnnotationProperty }] } ,
          OT.reportType => { RDF["type"] => [{ "type" => "uri", "value" => OWL.AnnotationProperty }] } ,
          OT.message => { RDF["type"] => [{ "type" => "uri", "value" => OWL.AnnotationProperty }] } ,
          OT.statusCode => { RDF["type"] => [{ "type" => "uri", "value" => OWL.AnnotationProperty }] } ,
          OT.actor => { RDF["type"] => [{ "type" => "uri", "value" => OWL.AnnotationProperty }] } ,
          OT.errorCode => { RDF["type"] => [{ "type" => "uri", "value" => OWL.AnnotationProperty }] } ,

          OT.hasSource => { RDF["type"] => [{ "type" => "uri", "value" => OWL.DatatypeProperty }] } ,
          OT.value => { RDF["type"] => [{ "type" => "uri", "value" => OWL.DatatypeProperty }] } ,
          OT.paramScope => { RDF["type"] => [{ "type" => "uri", "value" => OWL.DatatypeProperty }] } ,
          #OT.paramValue => { RDF["type"] => [{ "type" => "uri", "value" => OWL.DatatypeProperty }] } ,
        }

        @data_entries = {}
        @values_id = 0
        @parameter_id = 0
        
        @classes = Set.new 
        @object_properties = Set.new
        @annotation_properties = Set.new
        @datatype_properties = Set.new

        @objects = Set.new
      end

      # Add a compound
      # @param [String] uri Compound URI
      def add_compound(uri)
        @object[uri] = { RDF["type"] => [{ "type" => "uri", "value" => OT.Compound }] }
      end

      # Add a feature
      # @param [String] uri Feature URI
      def add_feature(uri,metadata)
        @object[uri] = { RDF["type"] => [{ "type" => "uri", "value" => OT.Feature }] }
        add_metadata uri, metadata
      end

      # Add a dataset
      # @param [String] uri Dataset URI
      def add_dataset(dataset)
        @dataset = dataset.uri
        @object[dataset.uri] = { RDF["type"] => [{ "type" => "uri", "value" => OT.Dataset }] }
        add_metadata dataset.uri, dataset.metadata
        dataset.compounds.each { |compound| add_compound compound }
        dataset.features.each { |feature,metadata| add_feature feature,metadata }
        dataset.data_entries.each do |compound,entry|
          entry.each do |feature,values|
            values.each { |value| add_data_entry compound,feature,value }
          end
        end
      end

      # Add a algorithm
      # @param [String] uri Algorithm URI
      def add_algorithm(uri,metadata)
        @object[uri] = { RDF["type"] => [{ "type" => "uri", "value" => OT.Algorithm }] }
        add_metadata uri, metadata
      end

      # Add a model
      # @param [String] uri Model URI
      def add_model(uri,metadata)
        @object[uri] = { RDF["type"] => [{ "type" => "uri", "value" => OT.Model }] }
        add_metadata uri, metadata
        @object[metadata[OT.featureDataset]] = { RDF["type"] => [{ "type" => "uri", "value" => OT.Dataset }] }
        @object[metadata[OT.trainingDataset]] = { RDF["type"] => [{ "type" => "uri", "value" => OT.Dataset }] }
        @object[metadata[OT.dependentVariables]] = { RDF["type"] => [{ "type" => "uri", "value" => OT.Feature }] }
        metadata[OT.predictedVariables].each{|feature| @object[feature] = { RDF["type"] => [{ "type" => "uri", "value" => OT.Feature }] }}
        # TODO: add algorithms from parameters
        @object["http://ot-dev.in-silico.ch/algorithm/fminer/bbrc"] = { RDF["type"] => [{ "type" => "uri", "value" => OT.Algorithm }] }
        @object["http://ot-dev.in-silico.ch/algorithm/fminer/last"] = { RDF["type"] => [{ "type" => "uri", "value" => OT.Algorithm }] }
        @object["http://ot-dev.in-silico.ch/algorithm/lazar"] = { RDF["type"] => [{ "type" => "uri", "value" => OT.Algorithm }] }
      end

      # Add a task
      # @param [String] uri Model URI
      def add_task(uri,metadata)
        @object[uri] = { RDF["type"] => [{ "type" => "uri", "value" => OT.Task }] }
        add_metadata uri, metadata
      end
      
      # Add a resource defined by resource_class and content
      # (see documentation of add_content for example)
      # @param [String] uri of resource
      # @param [String] resource class, e.g. OT.Validation
      # @param [Hash] content as hash
      def add_resource(uri, resource_class, content)
        @object[uri] = { RDF["type"] => [{ "type" => "uri", "value" => resource_class }] }
        @@content_id = 1
        add_content uri, content
      end
      
      private
      @@content_id = 1
      
      # Recursiv function to add content
      # @example
      # { DC.description => "bla",
      #   OT.similar_resources => [ "http://uri1", "http://uri2" ],
      #   OT.matrixCells => 
      #     [ { RDF.type => OT.MatrixCell, OT.cellIndex=1 OT.cellValue => "xy" },
      #       { RDF.type => OT.MatrixCell, OT.cellIndex=2 OT.cellValue => "z" } ],
      #   OT.info => { RDF.type => OT.ImportantInfo, 
      #                DC.description => "blub" }
      # } 
      # @param [String] uri
      # @param [Hash] content as hash, uri must already have been added to @object
      def add_content(uri, hash)
        raise "content is no hash: "+hash.class.to_s unless hash.is_a?(Hash)
        hash.each do |u,v|
          if v.is_a? Hash
            # value is again a hash, i.e. a new owl class is added
            # first make sure type (==class) is set 
            type = v[RDF.type]
            raise "type missing for "+u.to_s+" content:\n"+v.inspect unless type
            raise "class unknown "+type.to_s+" (for "+u.to_s+")" unless @object.has_key?(type)
            # create new node and add to current uri
            genid = "_:#{type.split('#')[-1]}#{@@content_id}"
            @@content_id += 1
            @object[uri] = {} unless @object[uri]
            @object[uri][u] = [{ "type" => "bnode", "value" => genid }]
            # add content to new class
            add_content(genid,v)
          elsif v.is_a? Array
            # value is an array, i.e. a list of values with property is added 
            v.each{ |vv| add_content( uri, { u => vv } ) }
          else # v.is_a? String
            # simple string value
            @object[uri] = {} unless @object[uri]
            @object[uri][u] = [] unless @object[uri][u]
            raise "property unknown "+u.to_s if !@object.has_key?(u) and u!=RDF.type
            # use << to allow different values for one property
            @object[uri][u] << {"type" => type(v), "value" => v }
          end
        end
      end
      
      public

      # Add metadata
      # @param [Hash] metadata
      def add_metadata(uri,metadata)
        id = 0
        metadata.each do |u,v|
          #if v.is_a? Array and (u == OT.parameters or u == RDF.type)
          if v.is_a? Array and u == OT.parameters#or u == RDF.type)
            @object[uri][u] = [] unless @object[uri][u]
            v.each do |value|
              id+=1
              genid = "_:genid#{id}"
              @object[uri][u] << {"type" => "bnode", "value" => genid}
              @object[genid] = { RDF["type"] => [{ "type" => "uri", "value" => OT.Parameter}] }
              value.each do |name,entry|
                @object[genid][name] = [{"type" => type(entry), "value" => entry }]
              end
            end
          elsif v.is_a? Array #and u == RDF.type
            @object[uri] = {} unless @object[uri]
            v.each do |value|
              @object[uri][u] = [] unless @object[uri][u]
              @object[uri][u] << {"type" => type(value), "value" => value }
            end
          elsif v.is_a? String
            @object[uri] = {} unless @object[uri]
            @object[uri][u] = [{"type" => type(v), "value" => v }]
          end
        end
      end

      # Add a data entry
      # @param [String] compound Compound URI
      # @param [String] feature Feature URI
      # @param [Boolead,Float] value Feature value
      def add_data_entry(compound,feature,value)
        add_compound(compound) unless @object[compound]
        add_feature(feature,{}) unless @object[feature]
        unless data_entry = @data_entries[compound]
          data_entry = "_:dataentry#{@data_entries.size}"
          @data_entries[compound] = data_entry
          @object[@dataset][OT.dataEntry] = [] unless @object[@dataset][OT.dataEntry]
          @object[@dataset][OT.dataEntry] << {"type" => "bnode", "value" => data_entry}
          @object[data_entry] = {
            RDF["type"] => [{ "type" => "uri", "value" => OT.DataEntry }],
            OT.compound => [{ "type" => "uri", "value" => compound }],
            OT.values => [],
          }
        end
        values = "_:values#{@values_id}"
        @values_id += 1
        @object[data_entry][OT.values] << {"type" => "bnode", "value" => values}
        case type(value)
        when "uri"
          v = [{ "type" => "uri", "value" => value}]
        when "literal"
          v = [{ "type" => "literal", "value" => value, "datatype" => datatype(value) }]
        else 
          raise "Illegal type #{type(value)} for #{value}."
        end
        @object[values] = {
          RDF["type"] => [{ "type" => "uri", "value" => OT.FeatureValue }],
          OT.feature => [{ "type" => "uri", "value" => feature }],
          OT.value => v
        }
        @object[feature][RDF["type"]] << { "type" => "uri", "value" => featuretype(value) }
        #@object[feature][RDF["type"]] = { "type" => "uri", "value" => featuretype(value) }
      end

      # Serializers
      
      # Convert to N-Triples
      # @return [text/plain] Object OWL-DL in N-Triples format
      def to_ntriples

        @triples = Set.new
        @object.each do |s,entry|
          s = url(s) if type(s) == "uri"
          entry.each do |p,objects|
            p = url(p)
            objects.each do |o|
              case o["type"] 
              when "uri"
                o = url(o["value"])
              when "literal"
                o = literal(o["value"],datatype(o["value"]))
              when "bnode"
                o = o["value"]
              end
              @triples << [s,p,o]
            end
          end
        end
        @triples.sort.collect{ |s| s.join(' ').concat(" .") }.join("\n")+"\n"
      end

      # Convert to RDF/XML
      # @return [text/plain] Object OWL-DL in RDF/XML format
      def to_rdfxml
        Tempfile.open("owl-serializer"){|f| f.write(self.to_ntriples); @path = f.path}
        # TODO: add base uri for ist services
        `rapper -i ntriples -f 'xmlns:ot="#{OT.uri}"' -f 'xmlns:ota="#{OTA.uri}"' -f 'xmlns:dc="#{DC.uri}"' -f 'xmlns:rdf="#{RDF.uri}"' -f 'xmlns:owl="#{OWL.uri}"' -o rdfxml #{@path} 2>/dev/null`
      end

      # Convert to JSON as specified in http://n2.talis.com/wiki/RDF_JSON_Specification
      # (Ambit services use a different JSON representation)
      # @return [text/plain] Object OWL-DL in JSON format
      def to_json
        #rdf_types
        Yajl::Encoder.encode(@object)
      end

      # Helpers for type detection
      private

      def datatype(value)
        if value.is_a? TrueClass or value.is_a? FalseClass
          XSD.boolean
        elsif value.is_a? Float
          XSD.float
        else
          XSD.string
        end
      end

      def featuretype(value)
        if value.is_a? TrueClass or value.is_a? FalseClass
          datatype = OT.NominalFeature
        elsif value.is_a? Float
          datatype = OT.NumericFeature
        else
          datatype = OT.StringFeature
        end
      end

      def type(value)
        begin
          uri = URI.parse(value)
          if uri.class == URI::HTTP or uri.class == URI::HTTPS
            "uri"
          elsif value.match(/^_/)
            "bnode"
          else
            "literal"
          end
        rescue
          "literal"
        end
      end

      def literal(value,type)
        # concat and << are faster string concatination operators than + 
        '"'.concat(value.to_s).concat('"^^<').concat(type).concat('>')
      end

      def url(uri)
        # concat and << are faster string concatination operators than + 
        '<'.concat(uri).concat('>')
      end

      def rdf_types
        @classes.each { |c| @object[c] = { RDF["type"] => [{ "type" => "uri", "value" => OWL['Class'] }] } } 
        @object_properties.each { |p| @object[p] = { RDF["type"] => [{ "type" => "uri", "value" => OWL['ObjectProperty'] }] } } 
        @annotation_properties.each { |a| @object[a] = { RDF["type"] => [{ "type" => "uri", "value" => OWL['AnnotationProperty'] }] } } 
        @datatype_properties.each { |d| @object[d] = { RDF["type"] => [{ "type" => "uri", "value" => OWL['DatatypeProperty'] }] } } 
      end

    end

    # Serializer for spreadsheet formats
    class Spreadsheets # to avoid nameclash with Spreadsheet gem

      # Create a new spreadsheet serializer
      # @param [OpenTox::Dataset] dataset Dataset object
      def initialize(dataset)
        @rows = []
        @rows << ["SMILES"]
        features = dataset.features.keys
        @rows.first << features
        @rows.first.flatten!
        dataset.data_entries.each do |compound,entries|
          smiles = Compound.new(compound).to_smiles
          row = Array.new(@rows.first.size)
          row[0] = smiles
          entries.each do |feature, values|
            i = features.index(feature)+1
            values.each do |value|
              if row[i] 
                row[i] = "#{row[i]} #{value}" # multiple values
              else
                row[i] = value 
              end
            end
          end
          @rows << row
        end
      end

      # Convert to CSV string
      # @return [String] CSV string
      def to_csv
        @rows.collect{|r| r.join(", ")}.join("\n")
      end

      # Convert to spreadsheet workbook
      # @return [Spreadsheet::Workbook] Workbook object (use the spreadsheet gemc to write a file)
      def to_spreadsheet
        Spreadsheet.client_encoding = 'UTF-8'
        book = Spreadsheet::Workbook.new
        sheet = book.create_worksheet(:name => '')
        sheet.column(0).width = 100
        i = 0
        @rows.each do |row|
          row.each do |c|
            sheet.row(i).push c
          end
          i+=1
        end
        book
      end

    end


  end
end