International Encyclopedia of Systems and Cybernetics

The set of the stable interrelations between the elements or components of an entity (or system).

M. BUNGE extends structure to the relations among the components of the system and the environment (1979, p.4).

Many different definitions have been enounced by numerous authors, as for example:

"The arrangement of the subsystems and components in three-dimensional space at a given moment of time" (J. MILLER, 1978, p.22).

The Argentinian biologist M. CEREIJIDO proposes a very similar definition, but makes the following comment: "The instantaneous disposition is frequently called "configuration", while "structure" would be the durable disposition, i.e. what succesive dispositions have in common" (1978, p.29).

According to FEIBLEMAN & FRIEND "Structure is the sharing of subparts between parts" (1945 – 1969, p.48).

They complete this definition in the following significant way: "In every action, there is a sharing and an interchange".

Thereafter they comment: "The sharing which constitutes the structure is from the point of view of the whole represented by the sharing which constitutes the function".

This was formulated in a striking way by E. JANTSCH, in terms of "Spatial self-balancing of a system of processes. Their interaction generates structures which may be compared to standing-wave patterns rather than solid constructs" (1975, p.27). See for example: "Soliton".

In the same vein, K. KRIPPENDORFF states: "Any communication process, once initiated and maintained, leads to the genesis of social structure, whether or not such structure is anticipated or deemed desirable" (1971, p.171). This is a very interesting insight in relation to various systemic concepts: morphogenesis, symbiosis, parasitism…

G. KLAUS definition is still less static: "Set of the material relations existing between active elements in a dynamical system" (1976, p.79).

In other words, it is impossible to leave aside the concept of time, even in such an apparently static notion as structure. In BLAUBERG, SADOVSKY and YUDIN's words: "The point is that a complete abstraction from any time is only possible in a strictly limited class of problems dealing with the investigation of the anatomy or the morphology of the object, when analysis of its purely synchronic cross-section becomes both possible and necessary.

"Knowing the composition of the object, its anatomy and morphology does not imply however, knowledge of its structure. Structure is not dead cast of the frozen object, but a characteristic of those of its invariant aspects which are only revealed during the analysis of its actual dynamics" (1977, p.236

A good example is petrified wood, in which the relative relations among parts have been conserved, while the nature of the parts themselves has changed: complex chemical reactions have replaced wood by stone, in the course of eons.

However, while being not only synchronic, but altogether diachronic, structures are repetitious in a cyclic, hypercyclic or cyclomorphic way, within the autopoietic frame of organizational closure.

This point is clearly made by W.R. ASHBY, who writes: "… the structure of "machines" appears when the laws that govern the system are invariant in time" (1964, p.93). Or, in other words: no structures without permanent constraints.

Differently, evolution signals itself by innovative events.

In R. FIVAZ the global structure of a system is: "described by one or several order parameters" (1991, p.32).

This connects the concept of structure with synergetics.

Structures can be represented by graphs, some types more easily than others, as for example linear chained structures, circular, or cyclical structures, or centered structures, described by B. WALLISER (1977, p.52). When oriented, graphs give some idea of the dynamics of the structure, as for example in the basic schemas of systems dynamics. As observed by J. van GIGCH, structures are frequently hierarchic (1978, p.15). However, in networks for example, this is not necessarily so.