TraceSpan

Where a traced event sits in a trace (design 4.58): the span it is (context), that span's parent, if any - which may be a span of another process, a remote parent - and when the span started. The event's own timestamp is when it ended. A backend that builds spans uses all three; one that does not ignores them.

A span is in its parent's trace: a parent of another trace is refused, by TraceSpan.of as a ValidationError and by apply and the with* setters as an IllegalArgumentException, so no backend ever sees a span whose trace id and parent's disagree.