Three families of functions are distinguished:
Central : commercial activities as well as services and some manufacturing industries,
whose production is intended to the regional market, i.e. neighboring towns and cities.
Different hierarchical levels are distinguished, as in central place theory.
Territorial : administrative activities which take place in the frame of
administrative boundaries. It could concern the specific functions of the
capital in the framework of the national territory or that of a regional capital
Specialized : the production functions which were created by the main cycles of economic
and technological innovation (maritime trade between 13th and 18th century, industrial
revolution of 19th century, second industrial revolution at the turn of 20th century,
emergence of technopoles in the second half of 20th century).
Each family of functions corresponds to a principle of interaction.