# File lib/mcollective/data.rb, line 41
    def self.ddl_validate(ddl, argument)
      name = ddl.meta[:name]
      query = ddl.entities[:data]

      raise DDLValidationError, "No dataquery has been defined in the DDL for data plugin #{name}" unless query

      input = query.fetch(:input, {})
      output = query.fetch(:output, {})

      raise DDLValidationError, "No output has been defined in the DDL for data plugin #{name}" if output.keys.empty?

      if input[:query]
        return true if argument.nil? && input[:query][:optional]

        ddl.validate_input_argument(input, :query, argument)
      else
        raise("No data plugin argument was declared in the %s DDL but an input was supplied" % name) if argument
        return true
      end
    end