# Toward a Practical Digital Twin Platform Tailored to the Requirements of Industrial Energy Systems
## 4 Discussion
### Digital Twin Platform Benefits  
Our contribution aims to overcome the technical implementation barriers relevant for energy systems summarized in Table 2 and to enable different value-creating applications (see Table 1) in the same platform. Via the simple exemplary workflow for a deviation detection application, given in Figure 5, and considering typical use cases, it is possible to assess the attributes of our platform that aim to maximize the benefits of individual applications. We have to stress here that the final benefits such as energy demand reduction, revenue increase and cost reduction that are expected from DT (see Section 2.2) are only provided via the respective applications integrated as services. However, we consider the detailed discussion of individual services to be out of scope of this contribution and refer to specialized literature instead. Nonetheless, via this evaluation, the platform's qualitative benefits are clearly evident. Instead of having one monolithic application that takes care of all aspects of fault detection starting from the data cleansing, deviation detection, and fault classification to decision making and also scheduling maintenance actions, the process can be split into microservices that are coordinated by the service orchestrator in the DT platform. For the deviation detection workflow itself, nothing changes, but it enables it to integrate it more tightly with other DT services. For example, if a deviation is detected by the deviation detection service (see Figure 5), a message can trigger a workflow for fault classification in order to check if the deviation is caused by a fault or due to a normal drift in the system's behavior. In case of the latter, this information can then be used to trigger a model adaption workflow. For a more in-depth discussion of a semantic microservice framework, we refer to [PERSON] et al. [22], where automatic sensor data evaluation serves as a proof of concept. To react to new data points within the IES, a dedicated topic for each sensor value is set up on the message broker. Any service that needs to react to new data points subscribes to the respective topics. Whenever a new data point is available, the SCADA system publishes a message on the corresponding topic, and the message broker will deliver the new data points to all services that require this data point. Through the publish/subscribe function of the message broker, neither the SCADA system nor the services need to have any information about each other aside from the name of the topic where data points are transferred. The ability of the DT to adapt to changes of the plant is enabled by the separation of models and the services that use these models. If a continuous drift in the system's behavior was detected via fault classification, models within the virtual entity can be automatically replaced or updated, e.g., via data-driven modeling and validation services, to fit the altered behavior. When a simulation service starts, it fetches the newest validated model instance from the virtual entity. Figure 6 illustrates how the presented DT platform leverages the integration of digital applications to offer associated benefits. In addition to the easy integration, operation and maintainability of applications, another important aspect is that synergies between these individual solutions can be conveniently exploited. Naturally, applications such as condition monitoring and deviation detection can provide basic unidirectional information for subsequent fault classification and analysis. However, also, back-feeding information between applications can provide additional benefits. For example, a schedule derived from operational optimization can be used for estimations within predictive maintenance applications. Conversely, the latter can determine operational constraints for operational optimization services. This is not possible without sufficient information management.