Skip to main content

Use Case Granularity

Craig Larman weighs in on how granular use cases should be:

"A common error in identifying use cases is to represent individual steps, operations, or transactions as use cases. For example, in [a] point-of-sale terminal domain, one may (inappropriately) define a use case called 'Printing the Receipt' when in fact the printing operation is merely a step in the much larger use case process, 'Buy Items'.

A use case is a relatively large end-to-end process description that typically includes many steps or transactions; it is not normally an individual step or activity in a process.

It is possible to break down activities or portions of a use case into sub-use cases (called 'abstract use cases') - even down to individual steps - but this is not the norm . . . ."

- Craig Larman's Applying UML and Patterns, page 53

Comments

Popular posts from this blog

Why Spreadsheets Suck for Prioritizing

The Goal As a company executive, you want confidence that your product team (which includes all the people, from all departments, responsible for product success) has a sound basis for deciding which items are on the product roadmap. You also want confidence the team is prioritizing the items in a smart way. What Should We Prioritize? The items the team prioritizes could be features, user stories, epics, market problems, themes, or experiments. Melissa Perri  makes an excellent case for a " problem roadmap ", and, in general, I recommend focusing on the latter types of items. However, the topic of what types of items you should prioritize - and in what situations - is interesting and important but beyond the scope of this blog entry. A Sad but Familiar Story If there is significant controversy about priorities, then almost inevitably, a product manager or other member of the team decides to put together The Spreadsheet. I've done it. Some of the mos

Use Case as a Black Box

Consider the following use case: Purchase Items Actor: Purchaser Precondition: Purchaser types at least thirty words per minute and has a web navigation efficiency rating of at least 40. Postcondition: For the average Purchaser acting at full efficiency, the number of seconds elapsed is no more than 30 + 20 * n, where n is the number of items purchased. The name of the use case represents a functional requirement. What does the product do, or enable the user to do? Purchase items. What are we to make of the preconditions and postconditions? What relationship do they have to the requirements for the product? Answer: the preconditions and postconditions are the nonfunctional requirements attached to the functional requirement . Another way of expressing the nonfunctional requirement would be as an attribute and associated constraint: Usability: For a Purchaser who types at least thirty words per minute and has a web navigation efficiency rating of at least 40, it shall take no

Henry Ford's "Faster Horse" Quote

You may have heard the ( apocryphal ) Henry Ford quote: If I'd asked customers what they wanted, they would have said "a faster horse". Over at the On Product Management blog , Saeed gives his take on this infamous quote. He "hates" it, and gives some compelling reasons. Saeed is spot on in his explanations. Personally, I think the quote is great, but it's a matter of interpretation. The valid point of the quote is not that it's a bad idea to facilitate a conversation with your market to better understand it. The valid points are: You must ask the right questions to get valuable answers. You must interpret the answers thoughtfully - often outside their direct meaning - to glean reliable information. Asking questions is not always the best way to "listen" to your market. (E.g., sometimes pure observational studies are more reliable.) Nonetheless, I find the quote is helpful to combat "armchair product management" in the