Skip to main content

XM Principle 4: Contract-First Design

The initial design decision of the WIKISPEED car was that it should consist of eight modules – body, chassis, motor, suspension, interior, etc. Before Team WIKISPEED even started to design individual components, they designed the interfaces between those modules.

Joe did not know what suspension would be used on his car, but he was able identify the external parameters and boundary conditions of the suspension. After researching the subject, he found that that if the suspension mounting could withstand 8 gees, it would more than meet all the necessary requirements, even for Formula One racing applications. So the team identified a suitably sized block of aluminum that could carry that load. Any suspension that could be attached to that block could be used on the WIKISPEED car without modification to the rest of the car.

So when designing a solution,
  • Design the interfaces based on outside parameters, e.g. load factors, or communication and power requirements.
  • Only architect the connections up front, not the individual components.
  • Leave room to grow, i.e. over engineer these interfaces, because changing these fundamental contracts may be expensive.
P.S. Be sure to check out the Wrapper pattern to ensure independence between your design and the design of any component suppliers.

Next: Iterate the Design

The 10 Principles of Extreme Manufacturing


Popular posts from this blog

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…

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…

10 Warning Signs, that your team is not self-organizing

How do you know that self-organization is working? The Bern Chapter of Scrum Breakfast Club looked into this questions, and identified the following warning signs (which I have taken the liberty of translating).

The team reports to the Scrum Master at the Daily ScrumPeople wait for instructions from the Scrum MasterTeam members don't hold each other responsible [for their commitments]The same impediment comes up twice"That's the way it is" => resignation"I" instead of "We"Flip charts are lonelyCulture of conflict-avoidanceDecisions processes are unclear, nor are they discussedPersonal goals are more important than team goals
To this list I would add my a couple of my favorites:
you don't see a triangle on the task board (not working according prioritization of stories)after the daily Scrum, people return directly to their desks (no collaboration)there are a least as many stories in progress as team members (no pairing)
P.S. You can join the …