+ std::unordered_map<const UnfoldingEvent*, std::unique_ptr<UnfoldingEvent>> global_events_;
+
+ /**
+ * @brief: The collection of events in the unfolding
+ *
+ * @invariant: All of the events in this set are elements of `global_events_`
+ * and is kept updated at the same time as `global_events_`
+ */
+ EventSet event_handles;
+
+ /**
+ * @brief The "irrelevant" portions of the unfolding that do not need to be kept
+ * around to ensure that UDPOR functions correctly
+ *
+ * The set `G` is another global variable maintained by the UDPOR algorithm which
+ * is used to keep track of all events which used to be important to UDPOR.
+ *
+ * @note: The current implementation does not touch the set `G`. Its use is perhaps
+ * limited to debugging and/or model-checking acyclic state spaces
+ */
+ EventSet G;