References

PFV assembles existing work and points it at security and business operations. The credit belongs upstream. Each entry below notes what the source supports and where it stops.

Sources

• John D. C. Little (1961), “A Proof for the Queuing Formula: L = λW”, Operations Research 9(3). Work in progress divided by throughput gives average time in the system. What it does not do: it is an average relationship, not the duration of any individual item. It needs a consistently defined boundary, representative measurement, and a system where arrivals and completions roughly balance. It tells you lead time follows from work in progress and throughput; it does not tell you which to change, and a shorter queue does not by itself produce more output.
• W. Edwards Deming, Out of the Crisis (MIT Press, 1986). That the process, not the person, produces the result, and that improvement means changing the system rather than exhorting the people in it. Plan-Do-Study-Act is the loop PFV’s Prove stage follows. Where it stops: studying a change does not establish that the change caused the result.
• Eliyahu M. Goldratt, The Goal (North River Press, 1984) and Theory of Constraints (1990). The five focusing steps — identify, exploit, subordinate, elevate, repeat — and the idea that improving a non-constraint rarely improves the system. PFV follows this order when the evidence names a likely constraint. Where it stops: identifying a constraint from a static map is an inference, not an observation of one. PFV requires converging evidence and otherwise names nothing.
• Lean and the Toyota Production System — Taiichi Ohno, Toyota Production System (Productivity Press, 1988); James Womack and Daniel Jones, Lean Thinking (Simon & Schuster, 1996). Value-stream mapping, the distinction between work and waiting, and process cycle efficiency. Where it stops: efficiency ratios are descriptive. PFV publishes no universal threshold for what a “good” figure is.
• Six Sigma / DMAIC — Mikel Harry and Richard Schroeder, Six Sigma (Currency, 2000). Measure before improving, and define the boundary of what is measured. Where it stops: PFV does not perform statistical inference and draws no conclusions from single estimates.
• Donald Reinertsen, The Principles of Product Development Flow (Celeritas, 2009). Queues as the economic problem in knowledge work, and the cost of delay. Where it stops: the cost of delay in any given process is a business judgement, not something a map produces.
• Douglas W. Hubbard, How to Measure Anything (Wiley, 2007). That an estimate with a stated uncertainty beats an unstated opinion. Where it stops: PFV asks for point estimates and labels them as estimates; it does not calibrate them for you.
• CMMI — CMMI® is a registered trademark of ISACA, used here for description only. This work is independent and is not affiliated with, endorsed by, or appraised under CMMI Institute or ISACA.

On the examples

Worked examples on this site and in the tool are modelled from industry data. They are illustrative, not audited case studies, and they are not evidence of completed engagements.