# Seeking a Definition of Digital Twins for Construction and Infrastructure Management
## 3 Digital Twins Current State of the Art
### Digital Twin Development Frameworks  
In the context of DT frameworks, numerous prominent open-source and proprietary solutions have emerged, each offering unique capabilities and applications across various domains, including smart cities, construction, Industry 4.0, and healthcare. This section highlights the most widely used frameworks; for more detailed information, readers are referred to [28], which provides an in-depth exploration, [29], which covers frameworks specification and requirements, and [30], which details approaches and methods. Additionally, systematic challenges associated with DTs are discussed by [31]. Eclipse Ditto [32] is an open-source framework that excels in creating and managing DTs, offering a middleware solution to abstract physical devices in digital representations. This abstraction enables both synchronous and asynchronous interactions through a comprehensive API, encompassing state management, secure access control, and extensive protocol integration. Particularly advantageous for construction, BIM, smart cities, and Industry 4.0, Ditto's capabilities facilitate diverse applications. In construction and BIM, Ditto optimises building systems management by generating DTs for components such as HVAC systems, elevators, and security apparatus. This functionality permits real-time monitoring, predictive maintenance, and operational enhancement. For instance, a DT for an HVAC system can continuously track performance metrics, forecast maintenance requirements, and optimise energy consumption based on real-time environmental data. Similarly, a DT for an elevator system can monitor usage patterns, anticipate potential failures, and schedule maintenance to minimise operational disruptions. For smart cities, Ditto adeptly manages infrastructure elements, like street lighting, traffic signals, and waste management systems. By creating DTs for these components, cities can enhance performance, reduce energy usage, and improve service reliability. For example, streetlights can be monitored for energy efficiency, and traffic signals can be dynamically adjusted based on real-time traffic data to improve flow and reduce congestion. In Industry 4.0, Ditto supports advanced manufacturing processes through the creation of DTs for factory equipment and production lines. This enables real-time monitoring, predictive maintenance, and optimisation of manufacturing operations. Abstracting physical machines into DTs allows manufacturers to simulate various scenarios, predict potential failures, and optimise performance without halting actual production. For instance, a DT for a CNC machine can monitor tool wear, predict maintenance needs, and adjust operational parameters to ensure optimal performance and reduce downtime. Ditto's modelling capabilities are anchored in Vortolang, a metamodel based on the Eclipse modelling framework (EMF). This foundation allows for the precise and comprehensive modelling of DTs, capturing all pertinent properties and operations. DTs are connected to physical devices through protocols like AMQP, Kafka, and MQTT, ensuring robust data transfer and control. The framework supports bi-directional communication between digital and physical twins, fostering continuous development and maintenance--a critical feature for applications necessitating iterative improvements and feedback loops for performance optimisation. Ditto's state management functionality is pivotal for synchronising physical devices and DTs, enabling real-time monitoring and predictive maintenance. By managing the reported, desired, and current states of devices, Ditto ensures synchronisation and the publication of state changes, allowing for precise system control and monitoring. The framework's fine-grained, resource-based access control guarantees secure interactions, essential for applications in sensitive or critical environments. Eclipse Ditto's open-source nature offers significant advantages, including extensive customisation and community-driven enhancements.