Natural language often involves an implicit time sequence.
It was a dark and stormy night.
The language understander needs to infer:
A shot rang out.
John opened the door and saw the body.
- Time sequence: John heard the shot, then opened the
door, then saw the body.
- What is true at different times: it is still a dark and stormy night,
but the shot can no longer be heard.
- Causal sequence: John opened the door because he heard the
shot. (A backward inference: we know John opened the door, so we
presume he heard the shot.)