-generate a different checksum), typically when the event descriptions
-for a given facility change from one version to the next, if a module
-is recompiled and reloaded during a trace.
+generate a different checksum). It typically happens when, while tracing
+is enabled, a module using the named facility is unloaded, modified
+(along with the description of some events), recompiled and reloaded.
+Then, the trace will contain events from two different, similarly named,
+facility versions.