4.3 XES
MXML has a standard notation for storing timestamps, resources, and transaction types. Moreover, one can add arbitrary data elements to events and cases. The latter resulted in ad-hoc extensions of MXML where certain data attributes were interpreted in a specific manner. For example, SA-MXML (Semantically Annotated Mining eXtensible Markup Language) is a semantic annotated version of the MXML format used by the ProM framework. SA-MXML incorporates references between elements in logs and concepts in ontologies. For example, a resource can have a reference to a concept in an ontology describing a hierarchy of roles, organizational entities, and positions. To realize these semantic annotations, existing XML elements were interpreted in a new manner. Other extensions were realized in a similar manner. Although this approach worked quite well in practice, the various ad-hoc extensions also revealed shortcomings of the MXML format. This triggered the development of XES (eXtensible Event Stream) [48].