I have 10 salespersons who need to maintain their own contact list in the CRM with confidentiality and strict access control, and should not be able to see each other's contacts, activities, pipeline, etc. This is to ensure that the salespersons don't poach each other's leads since we have a sales performance based gamified incentives program. 

Some contacts could be universally accessible and open for everybody to know. Can I use tags to set up rules? If I tag a contact 'private', only I should be able to see/access it?

How can I achieve this, please?  I tried searching in these forums, but couldn't locate a solution to my issue (it must be there somewhere though, am sure):

Version: Odoo 11 Community Version