Who breaks up the stories into tasks? By scrum master? or by team members?
When to break up the stories? before/during/after the sprint planning?
How to break up the stories? By technologies, e.g. data-modeling, sql, or by use cases (each story may have several use cases, and error handling).
Thanks.
Who breaks up the stories into tasks? By scrum master? or by team members?
Team members do it. SM facilitates. PO answers questions on "what" and clarifies user story.
When to break up the stories? before/during/after the sprint planning?
Definitely during Sprint Planning. Realistically there might be times when you might have to break stories down into smaller chunks and task them out during the sprint. That would only happen when a team takes up vague stories or high complexity stories. I know taking up vague stories are not recommended and is tough on the team but there might be those rare times when you have to get things started on something. Definitely not after though, it kind of defeats the purpose of tasking by doing it after doesn't it? :)
How to break up the stories? By technologies, e.g. data-modeling, sql, or by use cases (each story may have several use cases, and error handling).
Don't think in terms of functional areas like sql, data modeling, coding, ui etc while tasking. Instead think in terms of use cases, test cases, granular features (remember, tdd way of thinking always helps here). After use cases are all listed known during planning, think what all tasks need to get done to get those use cases, features working. after that, divide those them into chunks of 8 - 16 hours (not more). Off course the use cases could be mentioned as done criteria and should be related directly to the user story being worked on.