Fig. 4.7 Meta model of XES [48]. A log contains traces and each trace contains events. Logs, traces, and events have attributes. Extensions may define new attributes and a log should declare the extensions used in it. Global attributes are attributes that are declared to be mandatory. Such attributes reside at the trace or event level. Attributes may be nested. Event classifiers are defined for the log and assign a “label” (e.g., activity name) to each event. There may be multiple classifiers