In my opinion, whether an industrial entity is a PSU or the other in the private sector, the broader classification of personnel can be that of "LINE" and "STAFF" based on their functions. The "line" refers to the core functions whereas the "staff" refers to the support functions. Therefore, it depends on the ultimate activity of the industrial enterprise. For example, in a manufacturing industry, those engaged in production or marketing would belong to the line, though the production personnel could be technical people whereas the marketing personnel would be non-technical while the people belonging to HR, Accounts &Audit, Safety, Security and Health would be "staff" i.e supporting staff though they may have their specific professional qualifications.