OpenXES does not completely support the IEEE XES Standard:

  • OpenXES does not recognize trace classifiers.
  • OpenXES cannot handle non-trace events, that is, events that are a direct child of the log (and are hence not in a trace).

The ProM Nightly Builds as of November 7, 2019 do have some support for this, although it still uses OpenXES in the back. When using an importer for "IEEE XES files", then these non-trace events are appended to a trace using the first trace classifier (if any). The trace classifier then provides the trace id. If no trace with that id exists, it will be created. This, way, assuming that a trace classifier exists, all events will be trace events, and can hence be handled by OpenXES.