Kai: Does the "-1" means going back to the previous version?

Xin: It's Github's jargon. "+1" means "Good" and "-1" means "Bad".

RyutaRegarding the language selection (written in page 7), C++ for core algorithm,
Python for system level, and bash for user level is something common within CMS collaboration ?

Xin: large number of groups in CMS collaboration adopt those" and " Except skillful person with C++, it is easy for, especially, a beginner & new comer to use Python  for system level task, and it also can make the management of the code much easier.  Also top level bash script could free one's time.