Sprint 0...or not?

No, it isn't. See these threads for more information:

https://www.scrum.org/Forums/aft/645
https://www.scrum.org/Forums/aft/366

From SCRUM timeboxed events perspective, it is not a valid sprint. It is usually the name given to do initial activities like refining product backlog, architecture envisioning, priortization and release planning etc.

Yes it is if you are using Zero-based numbering like in C like language.

If you are using VB then it starts with 1.

> From SCRUM timeboxed events perspective,
> it is not a valid sprint. It is usually the name
> given to do initial activities like refining
> product backlog, architecture envisioning,
> priortization and release planning etc.

True. However just to be clear, it isn't the nature of these activities which make the "Sprint Zero" concept invalid. The problem is that it does not usually result in an increment which the Product Owner values, nor is it usually timeboxed for that purpose.

It could be argued that a PO *should* value the things you mention, and that readying the Scrum instance is a meaningful goal for the first sprint.

From official scrum guide - there is no Sprint 0.

In practical world, when a team sets out to adopt Scrum - usually Sprint 0 is used for the first time to adopt the scrum framework in the current business process.

Sprint 0 - as any other sprint - has a goal. The goal usually is to set the team for a change. The goal is agreed by the scrum team. One of the basic requirement of the scrum is to have a product backlog and this sprint 0 is ideal to solidify the approach to maintain the backlog either in Agile software tools/Wiki or shared project notebook or post it notes on the wall. or select another that simplifies the work.

Sprint 0 - may or may not have a potentially ship-able product increment - agreed by the scrum team.

http://www.mountaingoatsoftware.com/blog/sprint-zero-a-good-idea-or-not