Non-retroactivity
Of the engineering term absence of feedback ( english absence of feedback or absence of interaction or freedom of interference ) means that the output of a control element is not backdated to the input variable (z. B. that the room temperature not to the flow temperature of the heating reacts).
The absence of feedback is relevant in control units with safety-critical functions. You can z. B. can be achieved by separating networks, operating systems or power supply or by spatial separation.
The feedback from human interventions in a system often provides the operator with important information (e.g. through the feedback of the steering torque when setting the steering wheel angle). In such cases, freedom from feedback means an undesirable loss of information for the operator.
Software industry
In the software industry, the term is sometimes used synonymously with "free of undesirable side effects". This means that a change to the source code of an application should not have any undesirable, careless effects on other applications.
car industry
For electronic control components in automobiles, ISO 26262 lists three aspects (program flow , memory access, communication) that must be safeguarded in order to guarantee freedom from retroactive effects. If the electronic components in an automobile are not certified according to ISO 26262, they must be certified according to the highest ASIL safety level ( Automotive Safety Integrity Level , see ISO 26262 ).
biology
Whether there is no interaction in biological systems depends on the system level considered. In this way, the signals of biological systems are transported on the smallest level via nerve cells. These transfer elements have no retroactive effect. At a more abstract level, chains of effects that contain at least one such transmission link can also be viewed as free of feedback.
Social sciences, psychology, media theory
The term is also occasionally used in the social sciences and psychology to describe conditions in which cause and effect are strictly separated. Most of the time, cause and effect coincide when looking at macrosocial phenomena (e.g. media communication): Seemingly independent variables are related to one another in interaction. A well-known example is the spiral of silence in communication. Here, too, the level of abstraction and aggregation of the observation is crucial, as to whether a state of freedom from feedback is achievable or can be ascertained, for example when observing social or media phenomena.
literature
- Norbert Bischof: Structure and meaning: an introduction to systems theory for psychologists. 2nd corrected edition. Bern, Göttingen, Toronto, Seattle: Huber 1998.