I am working with some guys who are looking at creating User Stories and there is a lot of discussion about how they should be worded. When a call comes into the business, the call centre need to search for the details of the person being queried. The search may be on an identification number, name, date of birth etc etc. Is the user story:
As a call centre consultant I need to search for a customer so that I can process a customer update.
On the back will be the various search options that could be employed such as by company name, customer name, identification umber, date of birth, address, etc.
Or is it:
As a call centre consultant I need to search for a customer by company name so that I can process a customer update
As a call centre consultant I need to search for a customer by identification number so that I can process a customer update
As a call centre consultant I need to search for a customer by customer name so that I can process a customer update
There is no official right or wrong for user stories, except to remember that they are a “promise for a conversation” and that every story should follow the INVEST model:
They also more valuable if written in the As a… I need… So that format, but the above examples already have that covered.
So if you apply that logic to the first example, it could fall down on some of these. If one or many search types are more valuable, or they are a large piece of work (not estimable or small) then it would make sense to do the second example. That said, you would not do your second examples if all the searches could be delivered in a small chunk of work.
A good size for a user story in my opinion is about 3 days. Regardless, the common logic is a good user story should fit inside your iteration length, and preferably within half your iteration length.
The other thing to consider is the testable aspect, it is good to set some acceptance criteria that defines the definition of done. That is usually noted on the back of the card.
This is a starting point, but as always the answer it is “it depends”.
Finally, a good reference book around this topic is User Stories Applied by Mike Cohn (http://www.amazon.com/User-Stories-Applied-Software-Development/dp/0321205685)