Skip to main content

Why fixed length sprints?

One common question for people new to Scrum is, "why should the length of the sprint be fixed?" What harm does it do to extend a sprint or plan the length of the sprint according to the task at hand?

There are probably as many answers to this question as there are ScrumMasters (25'000 the last time I looked), but two factors stand out:
  1. dealing with complexity
  2. maintaining agility of the team (and by extension of the company).
Under Scrum, we keep complexity under control by defining the parameters of each sprint. Time (calendar), Quality (through the definition of done and possibly other functional requiremens), Cost (team size * time available) and Scope for each sprint. Since Time, Cost and Quality are defined, the only thing which can vary is the amount of functionality actually produced. This is what is inspected at the end of each sprint.

I like to refer to the agreement between prodoct owner and team as the "Sprint Contract". So arbitrarily changing one of the parameters violates the Sprint Contract, and this is clearly not allowed.

Harry Sneed's "devil's square" shows the relation between Scope, Quality, Time and Cost.

And the end of each Sprint, the Product Owner inspects the progress of the team -- defined exclusively through the amount of scope produced -- and has the option of changing the course of the team.

Changing any of the other parameters, say the duration of the sprint, is 1) a violation of the sprinnt contract and 2) hides from the project owner that progress is not being made as planned (or hoped). He is deprived of the chance to make a course correction.

I believe there is a close correlation between corporate agility and fixed length sprints, so the next question should be, how long to sprint...

Comments

Anonymous said…
Devil's square was invented and propagated by Harry M. Sneed in his books on Software Project Calculation.
Peter said…
Thanks, anonymous!

I think Sneed's square is a major improvement over the 'Iron Triangle', which ignores Quality, or at best considers it floating in the air and somehow not related to the other parameters.

Wrong!

Oddly enough, time money invested in quality (in the form of, say, automated unit tests) reduces the cost and increases the performance. But you need a to take a view which is longer than a sprint or two.

Popular posts from this blog

Sample Definition of Done

Why does Scrum have a Definition of Done? Simple, everyone involved in the project needs to know and understand what Done means. Furthermore, Done should be really done, as in, 'there is nothing stopping us from earning value with this function, except maybe the go-ahead from the Product Owner. Consider the alternative:
Project Manager: Is this function done?
Developer: Yes
Project Manager: So we can ship it?
Developer: Well, No. It needs to be tested, and I need to write some documentation, but the code works, really. I tested it... (pause) ...on my machine. What's wrong with this exchange? To the developer and to the project manager, "done" means something rather different. To the developer in this case, done means: "I don't have to work on this piece of code any more (unless the tester tells me something is wrong)." The project leader is looking for a statement that the code is ready to ship.

At its most basic level, a definition of Done creates a sh…

Scaling Scrum: SAFe, DAD, or LeSS?

Participants in last week's Scrum MasterClass wanted to evaluate approaches to scaling Scrum and Agile for their large enterprise. So I set out to review the available frameworks. Which one is best for your situation?

Recently a number of approaches have started gaining attention, including the Scaled Agile Framework ("SAFe") by Dean Leffingwell, Disciplined Agile Development (DAD), by Scott Ambler, and Large Scale Scrum (LeSS), by Craig Larman and Bas Vodde. (Follow the links for white papers or overviews of each approach).

How to compare these approaches? My starting point is Scrum in the team. Scrum has proven very effective at helping teams perform, even though it does not directly address the issues surrounding larger organizations and teams. An approach to scaling Scrum should not be inconsistent with Scrum itself.

Scrum implements a small number of principles and constraints: Inspect and Adapt. An interdisciplinary Team solves the problem. Deliver something of va…

Five Simple Questions To Determine If You Have the Agile Mindset

My company has started a top-down transition to Scrum and Kanban. Will that make us an Agile company? About 2 years ago, I attended a conference hosted by the Swiss Association for Quality on the topic of Agility. As a warm-up exercise, the participants were given the 4 values of the Agile Manifesto, then asked to arrange themselves in space. How Agile is your company? How Agile do you think it should be? Very Agile on left, very traditional on the right. There was a cluster of people standing well to the right of center. “Why are you standing on the right?” It turns out that they were all from the railway. “Our job is to run the trains on time.” They were uncertain whether this agility thing was really aligned with their purpose.
Is Agility limited to software? Steve Denning has collected the evidence and laid out the case that Agile is not limited to software, nor is it merely a process, nor is it something you can do with part of your time, nor is it something you can have your …