Component with behavior must define a provides port (Dezyne Reference Manual)

11.3.5 Component with behavior must define a provides port

Any component with a behavior specification must have a provides port through which the component is activated.

An example:

interface iworld
{
  in void hello ();
  behavior {on hello:{}}
}

component component_without_provides
{
  requires iworld r;
  behavior {}
}

The examples results in the following error messages:

component-without-provides.dzn:7:1: error: component with behavior must
    define a provides port
component-without-provides.dzn:7:1: error: component with behavior must
    have a trigger