Explained from a system dynamics perspective, TYST is an unwanted change to a system through a series of small activities that may be independent from one another.
The TYST behaviour describes the process of how, within a certain domain, the CZ is gradually transformed into an Encroaching Zone only through the intermediary of the TZ.
The TYST behaviour is based on four main assumptions, without which the undesired behaviour, the depletion of the CZ, is avoided.
(4) The systems to which the TYST behaviour is applicable are finite.
The Causal Loop Diagram (CLD) concept (Roberts et al., 1983) is used to illustrate the causes and effects of the TYST behaviour.
The typical behaviour of the TYST model emerges as a transmitted expansion of the Encroaching Zone over the CZ, only possible through the intermediate of the TZ.
The TYST process is therefore only successful if there is a lack of transparency within the system.
The assumptions of TYST can be stated mathematically as follows:
This behaviour gives a hint about how to avoid or fix the TYST behaviour through nullifying the TZ and countering any positive change in the Encroaching Zone.
When translating the TYST model CLD into a Stock and Flow Diagram (SFD), the EZ, TZ and CZ are defined as 'stocks' (Figure 5).
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