Frequency based serves are typically specified as operating at a given interval, rather than particular times. From a passenger point of view multiple journeys will typically be presented as a single  journey running at an approximate interval, for example “every six to 10 minutes”.   NeTEx uses TEMPLATE VEHICLE journeys to describe such journeys.  From an operational point of view there will still need to be specific service journeys scheduled to fulfil the required frequency of service  and NeTEx can also include these to support real time journeys.