Tag Archives: use cases

Las Vegas….gambling on agile?

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OK, I want a catchy title… But I also want to tell you about the upcoming Better Software Conference and Agile Development Practices in Las Vegas June 6-11 where I’ll be presenting a one-day tutorial on Writing Effective Agile Use Cases. No I am not co-opting Alistair Cockburn’s bestselling Writing Effective Use Cases….this title was suggested by the conference organizers. They think it is more catchy than what I proposed: Writing Agile Use Cases.

I hope to share with you effective techniques I’ve picked up for writing use cases in an agile development environment. While I am not a believer in writing for writing’s sake, I happen to find that writing documentation on agile projects to not be intrinsically evil. I’ve worked with several agile teams to trim down their project documentation, write effectively, and to focus on what matters to them. Not every user story should be part of a use case description. And not every user story needs to be documented. But I believe in the power of the written word when it is effective, streamlined, and to the point. And I find that use cases that focus on usability and defining user tasks to be well-received by agile teams. Especially if they are done in context with usability experimention, wizard of oz prototyping, and lightweight user interface specification. So come join me in Las Vegas. Or ask me about agile use case writing workshops…where we hone our writing skills and write project-specific use cases.

Can you really estimate complexity with use cases?

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I visited with some folks last week who failed to get as much leverage from writing use cases as they’d hoped. In the spirit of being more agile, at the same time they adopted use cases, they also streamlined their other traditional development practices. So they didn’t gather and analyze other requirements as thoroughly as they had in the past. Their use cases were high level (sometimes these are called essential use cases) and lacked technical details or detailed descriptions of process variations or complex information that needed to be managed by the system. But their problem domain is complex and varied, prickly, and downright difficult to implement in a straightforward way (and use cases written at this level of detail failed to reveal this complexity). Because of the level of detail, they found it difficult to use these use cases to estimate the work involved to implement them. In short, these use cases didn’t live up to their expectations.

Were these folks hoodwinked by use case zealots with an agile bent? In Writing Effective Use Cases, Alistair Cockburn illustrates a “hub-and-spoke” model of requirements. A figure in his book puts use cases in the center of a “requirements wheel” with other requirements being spokes. Cockburn states that, “people seem to consider use cases to be the central element of the requirements or even the central element of the project’s development process.”

Putting use cases in the center of all requirements can lull folks into believing that if they have limited time (or if they are trying to “go agile”) they’ll get a bigger payoff by only focusing on the center. And indeed, if you adopt this view of “use cases as center”, it’s easy to discount other requirements perspectives as being less important. If you only have so much time, why not focus on the center and hope the rest will somehow fall into place? If you’re adopting agile practices, why not rely upon open communications between customers (or product owners or analysts) and the development team to fill in the details? Isn’t this enough? Maybe, maybe not. Don’t expect to get early accurate estimates by looking only at essential use cases. You’d be just as well off reading tea leaves.

Cockburn proposes that, “use cases create value when they are named as user goals and collected into a list that announces what the system will do, revealing the scope of a system and its purpose.” He goes on to state that, “an initial list of goals will be examined by user representatives, executives, expert developers, and project managers, who will estimate the cost and complexity of the system starting from it.” But if the real complexities aren’t revealed by essential use cases, naive estimates based on them are bound to be inaccurate. The fault isn’t with use cases. It’s in the hidden complexity (or perhaps naive optimism or dismissal of suspected complexity). A lot of special case handling and a deep, complex information model makes high-level use cases descriptions a deceptive tool for estimation. That is unless everyone on the project team is brutally honest about them as just being a touchpoint for further discussion and investigation. If the devil is in the details, the only way to make reasonable estimates is to figure out some of those details and then extrapolate estimates based on what is found. So domain experts that know those details had better be involved in estimating complexity. And if technical details are going introduce complexity, estimates that don’t take those into account will also be flawed. Realistically, better estimates can be had if you implement a few core use cases (those that are mutually agreed upon as being representative and prove out the complexities of the system) and extrapolate from there. But if details aren’t explained or if you don’t perform some prototyping in order to make better estimates, you won’t discover the real complexities until you are further along in development.

I’m sure there are other reasons for their disappointment with use cases but one big reason was a misguided belief that high-level use cases provide answers instead of just being a good vehicle for exploring and integrating other requirements. In my view, use cases can certainly link to other requirements, but they just represent a usage view of a system. One important requirement for many systems, but not the only one. If they are a center, they are just one of many “centers” and sources of requirements.

False Dichotomies and Forced Divisions

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Last week I received an email with this tagline:

“Replacing an on-site customer with some use cases is about as effective
as replacing a hug from your Mom with a friendly note.”

I enjoy this person’s funny, witty, and constantly changing taglines. They certainly add zest to mail messages. But this one bugged me. It set up a false dichotomy. A false dichotomy occurs when someone sets up choices so that it appears there are only two possible conclusions when in fact there are further alternatives. Consider the phrase “if you’re not for me you must be against me.” Most of the time this is a false dichotomy. There are other possibilities. You may totally be indifferent to the person’s proposed idea or undecided. There may be several unmentioned possibilities (and they may not be mutually exclusive).

Driving to a Portland SPIN meeting last night I saw this bumper sticker: “I don’t have to like George Bush to love my country”. Wow. A false dichotomy pointed out in the political arena. What a novelty!

But back to what bugs me about this tagline. It first set up the false dichotomy that “mom’s hug” is better than “friendly note”. But wait! Mom’s hugs aren’t always better than friendly notes. Maybe you need that friendly note to help you through a tough day. Maybe that friendly note includes a useful reminder. In that case a friendly hug might be a good start, but it’s not enough. Mom can always give you a friendly hug and write you a friendly note.

The tagline then makes the powerful analogy between mom and onsite customer, and friendly note and use cases. If you don’t think this through you could end up being swayed to believe that use cases and notes are never as good as mom or onsite customers or apple pie (and that you have to pick one). But use cases and onsite customers can co-exist if you need them to. There are legitimate reasons to write things down. Maybe writing helps a customer sort through what she really wants. There can be value in recording what was said because it needs remembering by more than the development team. The next time someone tries to sway you by setting up a false dichotomy don€’t get caught in their faulty reasoning. Stop. Think things through. Then decide what your position is or whether you see more possibilities.

Timely events in Use Cases

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Last week in a use case writing course I was teaching, a student presented me with a use case where he had been puzzling over how to accurately express the passage of time. His use case occurred over a period of several days and went something like this

Day 1:
The user does this
And this
And the system does this
Day 2:
The system does this
Another action..
Day 3:
The system does this
The user does this
And then things are finished

Although it accurately reflected the passage of time in the current system, he wasn’t satisfied with it. He wanted to describe a new version that could be more responsive. Instead of waiting for nightly data feeds, what if the system could process data more quickly? Expressing this in terms of time passing (day 1, day 2, etc.) seemed too concrete and limiting. After probing a bit, I suggested he consider restating this passage of time as events that enabled the use case to move forward. For example, “Day one” could become “Prediction made”, “Day two” could become “Project Completed”, and so forth. This shift in thinking–from describing elapsed time to describing events in a complex process–brought clarity to this use case and will influence the system re-design.

People can get bogged down because they don’t know how to express passage of time or lengthy pauses in action. Some might be tempted to “fix” the above use case by splitting it into three smaller one with appropriate pre and post conditions. That technical solution would only obscure the user’s overarching goal.

My eventful solution, another alternative, was inspired by Michael Jackson’s Problem Frames. Jackson emphasizes that, “the point of software development is to build machines that interact with the world and change it.” Jackson is big on describing problems in terms of domains and software “machines” having direct interfaces where shared phenomena flow between them. He cautions, “Don’t think of an interface as a queue or pipe or stream of messages flowing between the domains; instead think of events and states and values as being shared between the connected domains. Each interface is an interface of shared phenomena.” This notion of shared phenomena has been difficult for me to wrap my head around. I don’t typically think about what’s going out there in the world when I’m focusing on writing usage descriptions. But Jackson’s viewpoint is slowly starting to influence my thinking. Sometimes eventful interjections can help explain why the user or the system is doing what they are doing and lift you out of writing uninformative “skin level deep” descriptions.