The Hitchhiker's Guide to Fused Twins -- A Conceptualization to Access Digital Twins in situ in Smart Cities

Smart Cities are happening everywhere around us and yet they are still incomprehensibly far from directly impacting everyday life. What needs to happen to make cities really smart? Digital Twins (DTs) represent their Physical Twin (PT) in the real world through models, sensed data, context awareness, and interactions. A Digital Twin of a city appears to offer the right combination to make the Smart City accessible and thus usable. However, without appropriate interfaces, the complexity of a city cannot be represented. Ultimately, fully leveraging the potential of Smart Cities requires going beyond the Digital Twin. Can this issue be addressed? I advance embedding the Digital Twin into the Physical Twin, i.e. Fused Twins. Thus, this fusion allows access to data where it is generated in a context that can make it easily understandable. The Fused Twins paradigm is the formalization of this vision. Prototypes of Fused Twins are appearing at an neck-break speed from different domains but Smart Cities will be the context where Fused Twins will predominantly be seen in the future. This paper reviews Digital Twins to understand how Fused Twins can be constructed from Augmented Reality, Geographic Information Systems, Building/City Information Models and Digital Twins and provides an overview of current research and future directions.