Github user cestella commented on the issue:
https://github.com/apache/metron/pull/836
So, answering your questions en-masse we use the following similar to how
they exist in regex:
* `*` - `0` or `n` instances
* `?` - `0` or `1` instance
* `+` - `1` or `n` instances
In retrospect, this may not be as obvious as it seemed at the time. Think
we need a key that indicates this? ;)---
