Current ABNF says:
eventc = "BEGIN" ":" "VEVENT" CRLF
eventprop *alarmc
"END" ":" "VEVENT" CRLF
Would the following combination of ABNF and comments be sufficient to address this issue? And then similar specification for other such instances in the ABNF?
eventc = "BEGIN" ":" "VEVENT" CRLF
1*(eventprop / alarmc) ;Must have at least one eventprop
"END" ":" "VEVENT" CRLF
-- Frank