UMLR — Interactions p 607

Current text:
The invalid set of traces is associated only with the use of a Negative CombinedInteraction. For simplicity we describe only valid traces for all other constructs

This is not quite true
1) An assert declares all non-compliant traces as invalid
2) It may also be possible to use consider on normal trace where the message to be considered is not in the trace to indicate that if it occurs it is invalid.
3) It is also possible to declare invalid traces with state invariants. For example, imagine a constraint such as

Source: Michael Jesse Chonoles