This chapter shall be construed to the end that the treatment of persons convicted of crime shall take into consideration their individual characteristics, circumstances, needs and potentialities as revealed by a case study, and that whenever it appears desirable in the light of the needs of public safety and their own welfare, such person shall be dealt with, at restricted liberty in the community, by a uniformly organized system of constructive rehabilitation, under probation or parole supervision instead of in a correctional institution.