There are two main paradigms in which an urban hierarchy
can be represented:
- Christaller Model. According to this model, a dominance
is established between several orders of the hierarchy.
This relationship implies that a center of a lower order must rely
on a center of higher order for goods and services not being
- Pred Model. Christaller's model was adapted by Pred
to become more flexible and to reflect more complex interactions.
First, centers of the same order are not necessarily at the same hierarchical
level. This shows that some centers offer more diversified goods
and services than other centers, even if they are of the same size
Interdependency implies that central places can exchange
similar goods and services since they are competing in an open
market allowing several producers. Complementarity enables several
centers of a similar order to specialize in specific activities
and be supplied in goods and services they do not have from
other centers. This implies the notion of economies of scale reinforcing
a regional specialization.