A Root Cause Analysis of Agile Practices

At Agile2010 I was chatting with George Dinwiddie about general process related stuff (probably with some reference to Kanban!) and I mentioned an idea I had submitted to a couple of conferences which had never got accepted. George suggested we try it as a Open Jam session, so we did!

The idea is to run a root cause analysis of various agile practices to drill down into why they work and what the benefits to be realised are. So rather than using a 5 whys approach to solve problems, it is used to understand solutions. For example, why do unit test? To minimise defects? Why do we want to minimise defects? To create less rework? Why do we want less rework? etc. The session tied in nicely with another Open Jam run by David Hussman on Dude’s Law, which also emphasised focusing on why rather than how.

Here are the outputs from the 3 practices we picked; Unit Testing, Iterations (Time Boxes) and Limiting WIP. Click to view the album with bigger pictures.

As a general exercise, I found it really useful and interesting. Definitely something to try submitting to future conferences again. The discussion and debate we had, and the surprising tangents we went on, was rewarding and enlightening. I was particularly fascinated by the comparison between Time Boxing and Limiting WIP and the way that creativity came out in both of them through different paths. I hope that by understanding why practice work in more detail, we can avoid following them dogmatically, and be in a better position to solve problems based on context. When a particular practice is not suitable we can draw on other practices which can provide the same benefits.

This is definitely something I want to explore further – hopefully with workshops at future conferences. If you try it out as well, blog your outputs and let me know!

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Kanban Trail Markers

When talking about Kanban Systems for Software Development, I always try to emphasis that the Kanban System is more than the tool, and is a System that should be owned by the team, rather than being imposed upon it. By owning it, and being part of creating it, a team are more likely to evolve the system as part of continuous improvement. Recently, I tried a new analogy to make this point, and while its not perfect, I think its good enough to blog about for further feedback.

The Primary Practices of Kanban that I describe, are not Boolean practices that teams either do or don’t use. Rather they are practices that teams should be constantly revisiting, and re-implementing, as they improve and their context changes. To recap, the primary practices I talk about are:

  • Map the Value Stream
  • Visualise the Value Stream
  • Limit Work in Progress
  • Establish a Cadence
  • Reduce the Kanban Tokens

I currently describing these practices as like trail markers on the team’s journey of process improvement. At any point in time, the team’s Value Stream, Visualisation, WIP Limits, and Cadence identify where the team currently is, and when combined with Kanban Reduction, point the way forward. As when on a hike, only the group knows where it is, and only the group can decide where it should be going. The hiking group must work together, helping each other out and making sure that everyone reaches the destination. If you’ve read Eli Goldratt’s “The Goal” you’ll recognise the comparison to the one he uses.

Trail Marker

Where the analogy breaks down is that a team’s trail markers are only ever unique to that team. They cannot be followed by other teams. Instead, they will only show the journey the team has been on in their quest for success.

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XP As A Kanban System

During recent discussions with XP folks on the topic of Kanban, it occurred to me that based on my understanding, XP can be described in terms of a Kanban System for Software Development. This is an attempt to do that, on the basis that it might be useful in helping teams understand Kanban concepts. I have structured the description around the five primary practices of Kanban that I have previously blogged about.

1. Mapping the Value Stream


Here’s an example of an XP Value stream

  1. A customer comes to the team with a problem they want solving, and collaboratively they write a set of User Stories
  2. The team then holds an Iteration Planning meeting to prioritise which User Stories they believe they can deliver within the next iteration (which is 2 weeks in this example)
  3. The team then pick the first of those User Stories, and plans how they will build it.
  4. They build a User Story (using good engineering practices)
  5. When the team has something to show, they review progress with the customer. In this case, every 2 days on average. I assume that the team will be collaborating with the customer more often than that, but am not showing that level of feedback for simplicity. Reviewing a User Story may result in re-planning and re-building (iterating). Completing a User Story will trigger another User Story being planned and built.
  6. At the end of the Iteration, the customer accepts all the completed User Stories. At this point the User Stories are re-prioritised again and another set chosen for the next Iteration.
  7. At the end of the Iteration, the software may also be released, and more User Stories may be written.

In practice, the workflow is not this precise, but I think its a close enough approximation. For example, new User Stories could be written at any point.

2. Visualising the Value Stream

XP Visualisation

An XP teams may use a very simple visualisation such as the one above, which focuses on the Plan-Build-Review section of the Value Stream. The User Stories (yellow) chosen for an Iteration are initially not started. When they are planned, then tasks (grey) are added, and the tasks are working on until they are all done, and the User Story is Done.

3. Limiting Work in Progress


An XP team will limit work in progress by working in pairs, with each pair only working on a single User Story at a time until it is Done. Thus in the above example, a team of four developers limits work in progress to two User Stories by two pairs.

4. Establishing a Cadence

XP Cadence

XP teams have a very specific and synchronised cadence which is created by time-boxing the Iteration. Prioritisation, Reviews, Retrospection and Releases all occur at the same time interval, and User Stories are planned to be completed within that time interval.

5. Reducing the Kanban Tokens


An XP team is always striving to improve, usually by using retrospectives. As such, in the above example, they may reach a point where all four developers are able to work on the same User Story, and as a result complete it sooner.

Assuming that this description of an XP based Kanban System is not widely off the mark, I hope that it serves to communicate that XP and Kanban are not alternatives, but different and compatible ways of describing a process. Further, I have found that by understanding a process in terms of a Kanban System, it has helped my think about alternative ways of evolving that process in order to improve it. There is of course, more to XP than I have mentioned here, such as release planning, and the usual good engineering practices.

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The Fifth Primary Practice of Kanban

I recently wrote what I considered to be the four primary practices of a Kanban System for Software Development:

  1. Map the Value Stream
  2. Visualise the Value Stream
  3. Limit the Work in Progress
  4. Establish a Cadence

During subsequent discussions on the aspect of Continuous Improvement in a Kanban System, I decided that there was a missing fifth primary practice:

  1. Reduce the Kanban Tokens

I originally named this practice “Eliminate Kanban”, but was persuaded that this was probably overly sensational, and as a result potentially confusing or misleading. Its intent is that once a Kanban System is in place, the team should be constantly looking to improve it by creating an environment where the work flows naturally. There is a quote that I believe comes from Rother and Shook which says “flow where you can, pull where you must”. By striving to reduce the number of kanban tokens in the system, a team will move towards an environment where they are more self organising and the work can flow. This can be achieved by either lowering the WIP limits or by collapsing the number of distinct stages.

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How Is Kanban Different From Other Approaches?

There has been a lot of discussion recently around trying to define what Kanban is. Is it a tool? A process? A philosophy? During a discussion on the kanbandev list, Ron Jeffries led me (probably unintentionally) to an idea for a different way of trying differentiate Kanban from other Agile approaches. Rather than attempt a direct comparison and identification of unique differences, I realised that the various approaches are different only in where they place their emphasis. XP places a lot of emphasis on the technical practices. Scrum places more emphasis on the project management practices. Kanban, places its emphasis on business and value flow practices. As Ron would say, its all the same elephant, but each approach has a different view of it. At the end of the day, its having the most appropriate elephant for any given context that is most important.

Using Kent Beck’s distinction of Primary and Corollary Practices in XP (2nd Edition), I think that Kanban can be differentiated by identifying its Primary and Corollary Practices. As such, these practices may not be unique to Kanban, but are considered the most important. High performance Scrum and XP teams will inevitable use these practices in some form, but I don’t consider them to be clearly described as Primary Practices in those methods.

The Kanban Primary Practices I see (at the moment…) are:

  1. Map the Value Stream. A Kanban approach looks at the whole stream of work, from where it enters the scope of the team, to where it leaves. Thus typically, a Kanban system will explicitly include the transformation of work from the problem or idea, through to its release. i.e. Concept to Cash (or Consumption), or Incubate to Liquidate.
  2. Visualise the Work. A Kanban approach will make all the work as visible as possible, across the whole Value Stream. In particular, this includes the visualisation of expanding/contracting, or zooming in and out, of work items to make their value/solution, or other hierarchical relationships visible.
  3. Limit Work in Progress. A Kanban approach will explicitly limit work in progress. This is distinct from managing work in progress through the use if time-boxes as described by David Anderson. This absolute limiting of work in progress is what makes Kanban a pull system, rather than a very small batch push system.
  4. Establish a Cadence. A Kanban approach will create a natural rhythm by setting up a cadence which will help the team deliver. This will typically de-couple the input (planning and prioritisation) from the output (release), allowing more freedom than the time-box, but still providing a framework to release regularly, measure performance and continuously improve.

A Kanban team will almost certainly use Corollary Practices which may be considered Primary in another process. For example, a high performance Kanban team will inevitably use technical practices from XP, such as TDD and Continuous Integration. Other Corollary Practices from other methods might be the use of MMFs and User Stories to manage the work items. Equally Use Case Scenarios and Steps could serve the same purpose. Metrics such as Cycle Time, Throughput, Velocity, Cumulative Flow Diagrams and Due Date Performance are further Corollary Practices which could be used alongside the Cadence. The list is probably endless. The above Kanban Primary Practices set the foundation for a team use whatever other techniques help them be successful.

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