code: public void writeEntry(LogEntry logEntry, int caseNumber) throws PerspectiveException, IOException{
  		if(logPerspective == LogPerspective.TRACE_PERSPECTIVE)
  			throw new PerspectiveException(PerspectiveError.WRITE_ACTIVITY_IN_TRACE_PERSPECTIVE);
  		
  		prepare();
  		if(!headerWritten){
  			write(logFormat.getFileHeader());
  			headerWritten = true;
  		}
  		output.write(logFormat.getEntryAsString(logEntry, caseNumber));
  	}
docs: This method is only allowed in the activity perspective.
  @param logEntry The log entry to write.
  @param caseNumber
  @throws PerspectiveException
  @throws IOException