In the interpratation rules, unless the context otherwise requires— “applicant” means the owner, lessee or occupier, of land or premises and includes his duly authorized agent or representative; “building” has the meaning assigned to it by section 3 of the Act; “building line” means a line drawn across a plot such that no building or permanent structure, except a wall of approved design enclosing the plot, may be within the area contained between that line and the nearest road on which the plot has frontage; “business or commercial area” means any area or zone wherein the building will be permitted of business and commercial premises and such other building as the Director of Physical Planning may approve and includes land used as open space or other public place;