Congruence and Compatibility in Functional Regional Taxonomy: Principles and Applications

ABSTRACT The article connects several concepts that were previously used and evaluated separately in functional regional taxonomy and in the delineation of functional regions. Typically, functional regions are not defined based on absolute values of population flows. Instead, they are delineated using interaction measures, which are normalizations of population flows. In the resulting system of functional regions, it is possible to determine a membership index for each basic spatial unit, expressing the degree to which that unit belongs to the functional region in which it is located. The membership index used should be in congruence with the interaction measure applied. This means they should be based on the same normalization method. Using the example of two different states, two different datasets, and two different interaction measures with their corresponding membership indices, we demonstrate the necessity of congruence: interaction measure—functional region boundaries—membership indices. An important part of the article's outputs is the visual representation of this congruence through map outputs. The results confirm that different interaction measures yield significantly different delineations of functional regions. Only when the interaction measure and the membership index are in congruence are the procedures' logical correctness and the results' compatibility maintained.