An attempt to define a general, theoretical framework for the investigation of relationships between structure and function in biological systems was made ten years ago (Baianu and Marinescu, 1968;Comorosan and Baianu, 1969). It was then proposed that as a consequence of relational principles, biological variability, dynamics and conditions of experimental observation (and/or other "hidden" causes which are internal, or external to biological systems), one is often concerned with biological functions which are neither fully nor uniquely specified in terms of the underlying molecular structures. This rather general uncertainty, or limitation, was called "fuzziness"? of structures with respect to the associated biological function, and many examples of its occurrence were given by Nicolas Rashevsky (1971) in relational biology and the theory of organismic sets.
A simple example of the kind of relation which we had in mind was given in loc. cit. The relation "three points A, B and C form a triangle" is preserved as long as A, B and C are not co-linear and therefore there are an infinite number of different structures satisfying this relation. The relation fails to be satisfied only for those positions of C for which A, B and C are co-linear.
Similarly, in biology, one encounters many situations in which a certain relation, or biological function is maintained over a whole range of structures, or processes (which are not necessarily all well-defined, or specified) and therefore the definition of biological functions in terms of "the performing structures" is limited by a certain "fuzziness". Problems tin the fields of automata and systems theory this concept takes on a stochastic meaning