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Today we tackle Chapter 6 of  Daniel S. Vacanti’s Actionable Agile Metrics for Predictability: Interpreting CFDs.  Learning to read CFDs provide teams and individuals with a huge amount of information through data visualization.  Chapter 6 continues to build on flow metrics data visualization and Little’s Law. Remember to buy your copy today and read along!

Vacanti begins Chapter 6 reminding the reader that all CFD’s are context specific.  Context includes the process being tracked, the capacity of the team, the circumstance influences entry rate and the organization’s ability to absorb change as reflected in the departure rate.  The context affects the number of bands, the width of the bands and the slope of the bands.  Given that context is important, the purpose of drawing CFDs is less about answering specific questions, but rather a trigger to trigger asking the right questions.  Different kinds of problems generate different patterns that can be trigger questions and conversation.

A mismatch between the rate of arrivals and departures generate two different patterns.  When arrivals come faster than departures, the top line grows faster than the bottom line (bottom line is done and deployed).  Faster arrivals generate higher WIPs.  When departures outpace arrivals, the WIP will be reduced.  Depending on where you are in the lifecycle of a project or a product these observations will mean different things (context).

CFDs exhibiting flat lines indicate time frames of zero throughputs, zero departures, and zero arrivals. In many organizations, I have seen CFDs exhibit this pattern around the end of the year (our culture of use it or lose it vacations).  In this context the pattern is understandable otherwise we need to ask the questions, why isn’t anything getting done and then what can get things moving again.

The stairstep pattern is often indicative of waiting until the of the specific period to deliver and get feedback (mini waterfall?).  These patterns suggest questions about whether the team can complete work and get feedback on more on a continual basis.  Remember that generating feedback faster will tend to reduce rework, technical debt, and SURPRISES.

Bulging bans are a reflection of something happening in a process step.  Asking why things are building up in a step and what can be done to rectify the problem.  Bulges almost always cause a problem with predictability.  One simple explanation on very lean or teams with high degrees of individual specialization can be vacation or illnesses (this is one reason specialization is often toxic).

Disappearing bands occur when a step has no WIP.  This type of pattern can be caused by any number of problems.  Vacanti suggests a few: potentially the reporting interval is too long or steps that have overcapacity, excess variability in the flow of work or a step that may not be required in any specific iteration or reporting period.  I will suggest another: waterfall processes (this could also cause the stair-step appearance).

An S-curve is caused when WIP is allowed to go to zero.  The S-curve within a project or for a long-lived product makes predictability difficult because it interrupts the flow. The question the team needs to ask is whether there is a better way to manage work to reduce or eradicate startup and end times.

Vacanti ends this chapter on patterns with a reminder that a boring CFD (one the does not exhibit any of the patterns noted above) does not mean that questions shouldn’t be asked and that continuous process improvement to make the workflow better ALWAYS is in scope.

Patterns are a tool to ask questions, generate conversation and to identify whether action should be taken to improve flow.  In every case, we need to avoid using a pattern to generate a knee-jerk response.  Every pattern may or may not be a bad thing, we need to incorporate context into the discussion.


Previous Installments

Introduction and Game Plan
Week 2: Flow, Flow Metrics, and Predictability
Week 3: The Basics of Flow Metrics
Week 4: An Introduction to Little’s Law
Week 5: Introduction to CFDs
Week 6: Workflow Metrics and CFDs

Actionable Agile Metrics for Predictability: An Introduction by Daniel S. Vacanti



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