The position hierarchy is much more flexible; it ignores the business unit structure so you can easily apply this model alongside your existing business unit structure without complications.
There is an entity called Position. You create your positions and their hierarchy and then assign those positions to users. Positions allow the spanning of business units so a user in one business unit can access the records of a user in a subordinate position, no matter which business unit that user is in.
Another benefit of the position hierarchy is that a user can only have one manager; with positions, you can have more than one person in a position, thus allowing greater access where there are shared management responsibilities.
All the security models so far have been concerned with access to records; the read or write privileges are for the record and all fields in the record, but you may require certain fields within an entity to be restricted. Field-level security is...