Regarding Backlog Refinement not being mandatory in Scrum.
Backlog refinement is not mandatory as per Scrum and is considered a complementary practice. This is my understanding, however, I found myself in a position having to defend this and the counter argument that the other person made was that, since Backlog Refinement is mentioned in the Scrum Guide, then it is a part of Scrum.
If the intention is to help someone learn the correct thing, then how would you convince them that Backlog refinement is a complementary practice, when they quote the Scrum Guide against you?
In conversations with Ken, he has made this clear to me and hopefully I can to you. Refinement is not a Scrum Event because not every team needs it, some teams do it ongoing and not in a single event and some teams and handle in different ways. If it were to be a Scrum Event, then it would have to happen and be forced upon teams that do not need it, hence a recommended practice, but not a mandatory event.
All teams must do Scrum Events...
Backlog refinement is not a formal event, unless a Nexus is involved. Otherwise, a refinement activity can be seen as one of the rules of Scrum which bind the framework together
Otherwise, a refinement activity can be seen as one of the rules of Scrum which bind the framework together
@Ian Mitchell, Just to clarify, if it can be considered a rule, then it would imply that it is mandatory or even a part of Scrum as "Scrum's roles, events, artifacts, and rules are immutable". Would it be better to consider it a guidance?
hence a recommended practice, but not a mandatory event.
@Eric Naiburg, I understand its not an event, but is it mandatory? Also, is Product Backlog Refinement considered a part of Scrum or a complementary practice?
@Eric Naiburg, I guess a better way to phrase the above question is, Is Product Backlog Refinement Scrum or Not Scrum?
From the Scrum Guide:
Product Backlog refinement is the act of adding detail, estimates, and order to items in the Product Backlog. This is an ongoing process in which the Product Owner and the Development Team collaborate on the details of Product Backlog items. During Product Backlog refinement, items are reviewed and revised. The Scrum Team decides how and when refinement is done.
Therefore, surely refinement is something that happens on any Product Backlog that is being inspected and adapted; but this could happen in any number of ways, including during other Scrum events, or through ad-hoc conversations, or just by the Product Owner adding details and the Development Team adding estimates, as needed.
There's certainly nothing that says it has to be a dedicated meeting, which is a common practice, followed by the majority of Scrum Teams I've encountered.
Would it be better to consider it a guidance?
I suggest it's a rule that "The Scrum Team decides how and when refinement is done", and that it is an "ongoing process". There is no rule in the Guide about what this ought to mean in any team's context.
Refinement could potentially be accommodated within a Sprint Review, given that this event yields an adapted Product Backlog. Perhaps we can infer guidance, fron the way refinement is treated in the Guide, that such an approach is unlikely to be enough.
Like the others have said, it isn't breaking Scrum, but not required by Scrum.