All elements to which it applies (sources, sinks, demuxers) should implement query functions on their pads, so that applications and neighbour elements can request the current position, the stream length (if known) and so on.
Elements should make sure they forward events they do not handle with gst_pad_event_default (pad, parent, event) instead of just dropping them. Events should never be dropped unless specifically intended.
Elements should make sure they forward queries they do not handle with gst_pad_query_default (pad, parent, query) instead of just dropping them.