Events have two Boolean characteristics, happened and available. Each characteristic can be in one of two states: TRUE or FALSE. These states can be changed using event statements.

<event statement>

──┬─<cause statement>─────────┬────────────────────────────────────────┤
  ├─<causeandreset statement>─┤
  ├─<fix statement>───────────┤
  ├─<free statement>──────────┤
  ├─<liberate statement>──────┤
  ├─<procure statement>───────┤
  ├─<reset statement>─────────┤
  ├─<set statement>───────────┤
  ├─<wait statement>──────────┤
  └─<waitandreset statement>──┘

The happened and available states of an event can be interrogated using the HAPPENED function and the AVAILABLE function. For more information, see AVAILABLE Function and HAPPENED Function.