International Encyclopedia of Systems and Cybernetics

B. WALLISER classifies hierarchies within four types (see infra: "Hierarchies (Typology of)"

According to him these "four types of hierarchies may be distinguished from each other in different ways:

- qualitative and structural hierarchies, are based on an embedment principle by which the higher level objects are the inferior level sets, while functional and genetic hierarchies are sequential, based on an influence principle, where the objects of the superior level are of the same nature as those of the inferior level;

- qualitative hierarchies include objects on a similarity base, which do not necessarily have direct relations (material or logical) amongst them, while the other hierarchies include objects which generally are strongly interactive because of their proximity or sequentiality;

- genetical hierarchies are explicitely related to a diachronic viewpoint and exist only because of this temporality, while the other hierarchies correspond to a synchronic vision and remain invariable during a given period, even in case dynamic phenomena take place within them" (1991, p.74).

He adds: "Some hierarchies may be superposed in the sense that, with a similar arbores cent structure among objects, the relations may be understood in two different ways. Thus, the qualitative hierarchies coincide with the other ones if the classification criteria of the objects are precisely their membership of the same set, their functional complementarity or their common origin (for example: phylogenetic classification of animals). Likewise, structural and functional hierarchies merge when an integrated subset is "represented" by one of the elements which assume a leadership (as in an enterprise organizational chart). Finally, functional and genetical hierarchies fuse if the objects submitted to some other of superior level have been generated by it (parental authority in a family).

"Some hierarchies are also embedded, if the objects in some type of hierarchy are already hierarchies pertaining to some other type. It is thus possible to have a qualitative hierarchy which uses as classification rule for the objects the similarity of their hierarchical structure, of their hierarchical regulation (centralized or decentralized organization) or their hierarchical generation. It is likewise possible to find some functional hierarchy composed of objects made of a structural hierarchy (f. ex. regulations in an oil refinery made of men and machines). Finally it is possible to observe some genetical hierarchy in which each generated object is in turn a structural or functional hierarchy (ontogenesis process)" (p.74).