# File lib/edi4r/standards.rb, line 183
      def Directory.prefix_ext_finder( std, par )
        ext = ''
        case std

        when 'I' # SAP IDocs
          prefix = '/sap'
          if par[:IDOCTYPE]
            prefix += '/idocs'+par[:SAPTYPE]+'/'+par[:IDOCTYPE]+'/'
            if par[:EXTENSION].is_a? String and not par[:EXTENSION].empty?
              if par[:EXTENSION] =~ /\/(.*\/)([^\/]+)/
                prefix += $1 + 'ED'
                ext = $2 + '.csv'
              else
                prefix += 'ED'
                ext = par[:EXTENSION] + '.csv'
              end              
            else
              prefix += 'ED'
              ext = '.csv'
            end              
          else
            case par[:SAPTYPE]
            when '40'; ext = '04000'
            else ; raise "Unsupported SAP Type: #{par[:SAPTYPE]}"
            end
            prefix += '/controls/SD'
            ext += '.csv'
          end

        when 'E' # UN/EDIFACT
          prefix = '/edifact' 
          if par[:d0002] # ISO9735 requested?
            case par[:d0002]
            when 1
              ext = '10000'
            when 2
              ext = '20000'
            when 3
              ext = '30000'
            when 4
              # Assume that any setting of d0076 implies SV 4-1
              # Revise when SV 4-2 arrives!
              ext = (par[:d0076] == nil) ? '40000' : '40100'
            else
              raise "Invalid syntax version: #{par[:d0002]}"
            end
            prefix += '/iso9735/SD'
            ext += '.csv'

          else          # UN/TDID requested?
            prefix += par[:is_iedi] ? '/untdid/ID' : '/untdid/ED'
            ext = (par[:d0052]+par[:d0054]).downcase + '.csv'
          end

        else
          raise "Unsupported syntax standard: #{std}"
        end

        return prefix, ext
      end