# The Microverse: A Task-Oriented Edge-Scale Metaverese
## 2 Background and Related Work
### Digital Twins  
The concept of the digital twin was initially introduced in 2002 and subsequently documented by the National Aeronautical and Space Administration (NASA) [18]. A digital twin (DT) is a digital model that accurately represents the components and behaviors of a physical object or system [19]. Unlike a traditional simulation, a DT is not restricted to one particular process and can contain different procedures. Moreover, establishing the DT system ensures that data communication between virtual and physical objects is bidirectional and real-time. These characteristics of DTs enable simulation, analysis, and optimization in a broader range of system areas compared to a simulation. At first, industrial manufacturing adopted DT technology mainly to enhance different stages of production through simulation, optimization, and the incorporation of machine learning technologies. An example is an event-driven simulation focusing on manufacturing and assembly jobs, utilizing digital twin technology and human-robot collaboration [20; 21; 22]. A proposed framework employs digital twin technology to enable accurate and multidisciplinary integration in assembly processes, particularly in industries that deal with high-precision products (HPPs) [23]. The HPP also develops a prediction and enhancement framework and a practical examination to validate its efficacy and practicality. The case study illustrates an ice cream machine as an application instance of a digital twin (DT) in the food industry [24], with a particular focus on the utilization of virtual reality (VR) and augmented reality (AR) technology for visualization and interaction purposes. The framework employs secure data transmission by implementing a secure gate between the computer and the cloud. Recently, efforts have been demonstrated focusing on many facets of smart cities, such as intelligent transportation, intelligent energy distribution, and intelligent educational institutions. An example is the optimization problem in self-driving cars' electric propulsion drive systems (EPDSs) [25]. The suggested framework utilizes a DT-based approach to establish a connection between the logical twin in the control software and the propulsion motor drive system, enabling the estimation of EPDS performance. Nevertheless, the platform concepts are offered without any supporting experimental data. In another aspect of smart driving, a driver digital twin system was proposed that focused more on simulating and predicting the behavior mode and status of the drivers [26]. Compared to other work, the DT framework covers various aspects such as drivers' distraction detection, attention estimation, drowsiness detection, emotional state prediction, etc. Although the architecture is innovative, the paper did not provide any case studies or feasibility tests. DT methods are also proposed to support environmental energy sustainability. The DT simulation methods and digital representation of the world mirror those of the dynamic data-driven applications systems (DDDAS) paradigm from the National Science Foundation in 2000 [27]. A DDDAS combines a digital simulation model with a physical estimation model to ensure runtime performance. The big data challenge is mitigated with the reduced order modeling and ensemble methods that afford systems-level performance and analysis. DDDAS methods were used to control wind turbines [28] and wind turbine farms [29]. Hence, for over a decade, there have been approaches to manage wind power plants by integrating DTs and cloud technologies with extensive data analysis to set up remote control stations [30]. DT techniques have been combined with blockchain; for example, a research team built a prototype of a smart campus [31; 32]. With the help of a modeling engine, their system enables users to create their avatars inside the virtual campus. Users' location and primary status are reflected in real time. Moreover, an ecosystem with some simple functions, like a market, is established with the help of blockchain technology.