1 constraint = "constraint" id "(" constraint_term ")"
2
3 constraint_term = "time_sep" "at" (string | string_array)
4 "is" int si_unit
5 [ "from" int "until" int ]
6 [ "at" "fl" int_array ]
7 | constraint_term "and" constraint_term
8 si_unit = "s" | "min"