The acronym INVEST helps to remember a widely accepted set of criteria, or checklist, to assess the quality of a backlog item.
If the backlog item fails to meet one of these criteria, the team may want to reword it, or even consider a rewrite (which often translates into physically tearing up the old story card and writing a new one).
Having smaller pieces of work is an important factor in getting work done in a short timeframe: "Deliver [work] frequently ... with a preference to the shorter timescale."
Written well, an item in the Product Backlog has the following characteristics:
In Backlog Refinement:
The purpose of Backlog Refinement should be to confirm the scope of work, not to undertake traditional design and requirements documentation work.
Backlog items should be written to a sufficient level of detail to enable the team to start work on them. They are not, in this way, similar to traditional requirements documentation. Requirements documentation is done to the level that (a) business stakeholders can agree (and sign-off) on what they will get, and (b) indicate a complete solution, prior to any work being done.
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