Interface must define a behavior (Dezyne Reference Manual)

11.3.2 Interface must define a `behavior`

Interfaces without behavior are not allowed. No adequate default behavior is available:

interface interface_without_behavior
{
  in void hello ();
}

This results in the following error message:

interface-without-behavior.dzn:3:3: error: event `hello' is not used in
    behavior of interface `interface_without_behavior'
interface-without-behavior.dzn:1:1: error: interface must define a
    behavior

11.3.2 Interface must define a behavior

11.3.2 Interface must define a `behavior`