Digital Twins (DTs) are appearing everywhere, in agriculture, construction, engineering, production, and medicine, to mention just a few prominent examples. Research and industry have produced various definitions,1,2 ranging from underspecified (digital replica or virtual counterpart), overly narrow (virtual representation based on augmented reality technology), to utopian (complete digital representation) approaches. The concepts found in the literature range between 1) high-fidelity design-time models used for design-space exploration, dimensioning, or validation, and 2) software systems used to monitor, comprehend, and optimize the behavior of another system during its runtime.