For more information about the concrete syntax of XES we refer to www.xes standard.org. However, the fragment shown in Fig. 4.8 already demonstrates that XES indeed operationalise the concept of an event log as described in Definition 4.3. Moreover, the extension mechanism makes the format extendible while at the same time providing semantics for commonly used attributes. In the context of XES, five standard extensions have been defined. These extensions are described in the so-called XES EXT XML format [48]. Here, we only mention a subset of standard attributes defined by these extensions.