def output_before_run_set(self, runSet):
        """
        The method output_before_run_set() calculates the length of the
        first column for the output in terminal and stores information
        about the runSet in XML.
        @param runSet: current run set
        """
        xml_file_name = self.get_filename(runSet.name, "xml")

        identifier_names = [run.identifier for run in runSet.runs]

        # common prefix of file names
        runSet.common_prefix = util.common_base_dir(identifier_names)
        if runSet.common_prefix:
            runSet.common_prefix += os.path.sep

        # length of the first column in terminal
        runSet.max_length_of_filename = max(len(file) for file in identifier_names) if identifier_names else 20
        runSet.max_length_of_filename = max(20, runSet.max_length_of_filename - len(runSet.common_prefix))

        # write run set name to terminal
        numberOfFiles = len(runSet.runs)
        numberOfFilesStr = ("     (1 file)" if numberOfFiles == 1
                        else "     ({0} files)".format(numberOfFiles))
        util.printOut("\nexecuting run set"
            + (" '" + runSet.name + "'" if runSet.name else "")
            + numberOfFilesStr
            + TERMINAL_TITLE.format(runSet.full_name))

        # write information about the run set into txt_file
        self.writeRunSetInfoToLog(runSet)

        # prepare information for text output
        for run in runSet.runs:
            run.resultline = self.format_sourcefile_name(run.identifier, runSet)

            if run.sourcefiles:
                adjusted_identifier = util.relative_path(run.identifier, xml_file_name)
            else:
                # If no source files exist the task doesn't point to any file that could be downloaded.
                # In this case, the name doesn't have to be adjusted because it's no path.
                adjusted_identifier = run.identifier

        # prepare XML structure for each run and runSet
            run_attributes = {'name': adjusted_identifier}
            if run.sourcefiles:
                adjusted_sourcefiles = [util.relative_path(s, xml_file_name) for s in run.sourcefiles]
                run_attributes['files'] = '[' + ', '.join(adjusted_sourcefiles) + ']'
            run.xml = ET.Element("run", run_attributes)
            if run.specific_options:
                run.xml.set("options", " ".join(run.specific_options))
            if run.properties:
                all_properties = [prop_name for prop in run.properties for prop_name in prop.names]
                run.xml.set("properties", " ".join(sorted(all_properties)))
            run.xml.extend(self.xml_dummy_elements)

        block_name = runSet.blocks[0].name if len(runSet.blocks) == 1 else None
        runSet.xml = self.runs_to_xml(runSet, runSet.runs, block_name)

        # write (empty) results to txt_file and XML
        self.txt_file.append(self.run_set_to_text(runSet), False)
        runSet.xml_file_name = xml_file_name
        self._write_rough_result_xml_to_file(runSet.xml, runSet.xml_file_name)
        runSet.xml_file_last_modified_time = util.read_monotonic_time()
        self.all_created_files.add(runSet.xml_file_name)
        self.xml_file_names.append(runSet.xml_file_name)
The method output_before_run_set() calculates the length of the
        first column for the output in terminal and stores information
        about the runSet in XML.
        @param runSet: current run set