# Digital Twin Model Quality Optimization and Control Methods Based on Workflow Management
## 3 Modeling of the Workflow Integrated with Model Evaluation
### Modeling of the Workflow Integrated with Model Evaluation  
Digital twin modeling, the digital modeling of the attributes, methods, behaviors, and other characteristics of physical entities in a virtual space, is a highly complex process requiring a lot of time for positioning, fine-tuning, and optimization. Workflow is an important business process control technique widely used in all kinds of organizations to facilitate the consistent, accurate, efficient, and reliable execution of business processes. A workflow is the automation of a whole or part of a business process. In this process, documents, information, or products are passed from one participant (program, machine, or person) to another to perform a task according to a set of procedural rules [20]. A workflow management system can automatically control the model quality by the orderly execution of the relevant operations within the defined constraints [21]. On this basis, model evaluation can be integrated into the workflow. The quality is automatically controlled using the evaluation value as the flow constraint. To achieve effective control over digital twin model quality during the design process, the modeling activities and evaluation indexes at each stage of the digital twin model lifecycle, such as design and development, verification, and confirmation, are incorporated into a workflow. The existing workflow process metamodels of the Workflow Management Coalition provide no support for the representation of the various aspects of quality management. Thus, the existing workflow process model representation is extended accordingly so that the digital twin model quality control content can be properly described in the workflow process model. Workflow process models are expressed in many forms, such as Petri nets, directed network graphs (DNGs), and their various extensions [22]. This study combined the Petri net widely used in process control and quality control mechanisms to represent the workflow process model, with mapping of the design activities into the workflow, and configuration of the model evaluation methods for the transitions in the workflow process model, as shown in Figure 3. The workflow process metamodel defined by the Workflow Management Consortium describes the workflow components and logical relationships through five categories of elements: activities, transfer conditions, roles, workflow-related data, and deployed applications. Referring to the workflow process metamodel defined by the Workflow Consortium, the workflow process model integrated with model evaluation can be formalized and expressed as follows:  
\[CFT=(TID,N,T,G,A,O,R,D,P) \tag{3}\]  
where _TID_ indicates the identification of the model, \(N\) represents the node set in the process model, i.e., the place set of the Petri net, \(N=\{N_{0}\), \(N_{1}\),..., \(N_{n}\}\). \(T\) is the transition set in the Petri net, \(T=\{T_{1}\), \(T_{2}\),..., \(T_{n}\}\). \(G\) is the transition success condition, i.e., the threshold set for satisfactory model quality. \(A\) corresponds to the arc set in the Petri net, where the arc indicates the flow direction of the node, denoted by \"\(\rightarrow\)\". \(O\) is the model evaluation method set correlated with the transition. \(R\) is the workflow participant set. \(D\) is the related data. \(P\) is the selected external application set.  
Figure 2: Number of patches before and after model lightweighting.