A first component of a graph-based program specification includes an output control port. A second component includes an input control port and an input data port. A third component includes an output data port. The output control port is connected to the input control port, and the output data port is connected to the input data port. The first component includes control code that when executed causes the output control port to provide, to the input control port, at least one of suppression information or invocation information. The second component includes control code that when executed causes a computing system configured by the graph-based program specification to begin processing data received at the input data port in response to the invocation information if no suppression information is received at the input control port before the invocation information is received at the input control port.