## 2 Materials and Methods
### Process Modeling and Process Mining  
A process consists of interrelated activities, or sub-processes, for performing a task [24]. Process modeling is a technology of process graphical representation. It records the \"process\" of the task and the logic, policy, and procedure implemented by the \"process\" of the task. So, a process model can provide a comprehensive understanding of a process [25]. Most of the process modeling research focuses on business process modeling. [PERSON] [26] argued that business process model has multiple dimensions, including the organizational structure model, goal model, data model, location model, and other models, and presented a knowledge state transition model as a new dimension of business process model. [PERSON] [25] described the main process modelling techniques, including flow chart technique, data flow diagrams, role activity diagrams, role interactiondiagrams, Gantt chart, IDEF, colored Petri-net, object-oriented methods, and workflow technique. Unified modelling language (UML) is considered as the standard object-oriented modelling language, which is not only applicable to software systems, but also to business processes and other non-software systems. [PERSON] [27] described the application of model driven architecture (MDA) and UML for the modeling and specification of collaborative business processes for enabling enterprises to establish business-to-business collaborations. [PERSON] [28] presented a new \(\alpha\)-algorithm that extracts a process model from the workflow log. This is a new technique for process modeling called process mining.  
Process mining can be regarded as the link between model-based process analysis and data-oriented analysis techniques [6]. Event logs are necessary resources for process mining, and the quality of log data determines, to some extent, the quality of the model mining results. XES (eXtensible Event Stream) was adopted in 2010 by the IEEE Task Force on Process Mining as the standard format for logging events. It is now in the process of becoming an official IEEE standard. XES is an XML-based log file format [29]. Process mining often starts with process discovery. Once there is a process model, conformance techniques can be used to compare the mined models (event logs) with the existing models. The results of the checking show the deviations between the model and log. After the conformance checking, enhancement techniques can be used to extend or improve an existing process model, using other information recorded in the same event log. The process mining algorithm is a method of studying how to discover the activities experienced by the whole process runtime through the process log, so as to establish the process model. At present, many process mining algorithms have been proposed, which come from different research projects, and represent several different research directions. Each algorithm has its own solution for solving some difficult problems in process mining. Many process mining algorithms have been proposed, including: (1) a mining algorithm based on Petri net [28], (2) a block-oriented mining algorithm [7], (3) a mining algorithm based on an activity dependency graph [8], (4) a mining algorithm based on ADONIS [9], (5) a Fuzzy mining algorithm [10], etc.