Tag Archives: History of Scheduling

The origins of PERT and CPM – What came before the computers!

The development of PERT and CPM as Mainframe software systems starting in 1957 is well documented with contemporary accounts from the key people involved readily available.  What is less clear is how two systems developed contemporaneously, but in isolation, as well as a number of less well documented similar systems developed in the same timeframe in the UK and Europe came to have so many similar features.  These early tools used the ‘activity-on-arrow’ (AoA or ADM) notation which is a far from obvious model.  Later iterations of the concept of CPM used the ‘precedence’ notation which evolved from the way flow-charts were and are drawn.

stockpile

One obvious connection between the early developments was the community of interest around Operation (or Operational) Research (OR) a concept developed by the British at the beginning of WW2.  OR had developed to include the concept of linear programming by the mid-1950s which is the mathematical underpinning of CPM, but while this link explains some of the cross pollination of ideas and the mathematics it does not explain terms such as ‘float’ and the AoA notation (for more on the development of CPM as a computer based tool see http://www.mosaicprojects.com.au/PDF_Papers/P042_History%20of%20Scheduing.pdf).

A recent email from Chris Fostel, an Engineering Planning Analyst with Northrop Grumman Corporation (CFostel@rcn.com) appears to offer a rational explanation.  I’ve reproduced Chris’ email pretty much verbatim below – the challenge posed to you is to see if the oral history laid out below can be corroborated or validated.  I look forward to the responses.

Chris’ Oral History

quartermaster_corpsI was told this story in 1978 by a retired quartermaster who founded his own company after the War to utilize his global contacts and planning skills.  Unfortunately the individual who told me this story passed away quite a few years ago and I’m not sure any of his compatriots are still alive either.  Regardless, I thought I should pass this along before I join them in the next life.  I do not wish to minimize the work of Kelly and Walker. They introduced critical path scheduling to the world and formalized the algorithms.  They did not develop or invent the technique.

The origin of critical path scheduling was the planning of the US Pacific Island hopping campaign during World War II.  The Quartermaster Corps coordinated orders to dozens if not hundreds of warships, troop ships and supply ships for each assault on a new island.  If any ships arrived early it would alert the Japanese of an imminent attack.  Surprise was critical to the success of the island hopping campaign.  The US did not have enough warships to fight off the much larger Japanese fleet until late in the war. Alerting the Japanese high command would allow the Japanese fleet to intercept and destroy the slow moving US troop ships before they had a chance to launch an attack. 

Initially the quartermasters drew up their plans on maps of the pacific islands, including current location and travel times of each ship involved.  The travel times were drawn as arrows on the map.  Significant events, personnel or supplies that traveled by air were shown as dashed lines hopping over the ship’s arrows.  The quartermasters would then calculate shortest and longest travel times to the destination for all ships involved in the assault. The plans became very complicated.  Many ships made intermediate stops at various islands to refuel or transfer cargo and personnel.  The goal was to have all ships arrive at the same time.  It didn’t take the quartermasters long to realize that a photograph of the planning maps would be a devastating intelligence lapse.  They started drawing the islands as identical bubbles with identification codes and no particular geographical order on the bubble and arrow charts. These were the first activity on arrow critical path charts; circa 1942. 

The only validation I can offer you is that by now you should realize that activity on arrow diagrams were intuitive as was the term ‘float.’  Float was the amount of time a particular ship could float at anchor before getting underway for the rendezvous.  Later when the US quartermasters introduced the technique to the British for planning the D-Day invasion the British changed float to “Slack”, to broaden the term to include air force and army units which did not float, but could ‘slack off’ for the designated period of time. 

You will not find a written, dated, account of this story by a quartermaster corps veteran.  Critical path scheduling was a military secret until declassification in 1956.  In typical fashion, the veterans of WWII did not write about their experiences during the War.  No one broke the military secrecy.  After 1956 they were free to pass the method on to corporate planners such as Kelly and Walker.  A living WWII Quartermaster veteran, should be able to provide more than my intuitive confirmation.

This narrative makes sense to me from a historical perspective (military planning has involved drawing arrows on maps for at least 200 years) and a timing perspective.  Can we find any additional evidence to back this up??  Over to you!

Predicting Completion

At one level, completing on schedule has been a requirement, enforced to a greater or lesser extent for millennia. In the 1905 English court case Clydebank Engineering and Shipbuilding Co Ltd v Don Jose Ramos Yzquierdo y Castaneda [1905] AC 6; the court was prepared to uphold a ‘liquidated damages’ clause for delivery at the rate of ₤500 per week for each vessel not delivered by the contractors in the contract time. And rather more sever penalties could be imposed by Roman Emperors for late delivery.

As governments do today, the Romans outsourced most of their major works to contractors, with both public accountability and a legal framework as key governance constraints. What was significantly different was the consequences of failure! If a project went badly wrong in Roman times, the responsible public official would suffer a major career limiting event that could affect the prospects of his descendants for generations to come. Whilst the retribution applied to the contractor could be even more serious including death as well as retribution for generations to come.  Applying the Roman approach could give a whole new meaning to the ‘pain share’ part of a modern Alliance contracts…… as well as removing by execution many of the worst performing contractors. Rome was not built in a day but their empire did last for close to 1000 years [Frontinus – A Project Manager from the Roman Empire Era by Walker & Dart (Project Management Journal Vol.42, No.5, 4-16].

However, whilst there was undoubtedly an imperative for timely completion of contracts (projects in today’s terminology), there seems to be little in the way of predictive processes used by managers to assess the current expected completion date prior to the 1950s.

Having said that, I’m as sure that ‘smart people’ would have been assessing the expected completion of any significant ‘body of work’; both during the planning processes and during the course of the work. You simply cannot run a factory profitably if you cannot tell a customer when to expect his order – but predictive assessments and predictive processes are quite different.

Cost management and accounting has documented roots more than 6000 years old (provided you can read clay tablets), with modern book keeping emerging in the 15th century. I have found plenty of evidence of proficient governance and effective cost control on projects in the 17th, 18th and 19th centuries but so far nothing ‘predictive’ (cost or time) until the 20th century. Prior to the 20th century, ‘cost control’ focused on comparing actual costs against the planned cost (a process still common in many organisations).

Similarly, the idea of probability and making calculations about future outcomes from a risk management perspective can be traced back to the 17th century and the work of Newton, Leibniz, Bernoulli and Pascal.  These mathematicians advanced probability to the point where life insurance and annuities could be bought and sold, but again there seems to be little cross over into the realm of predicting project outcomes until the 20th century.

From a time management perspective, William Playfare ‘invented’ graphical statistics (including bar charts) and published a series of different charts in his Commercial and Political Atlas of 1786.

Playfair_TimeSeries-2

However, whilst Playfair’s charts are detailed and accurate, they only report history; trends and forecasts were not considered (or at least not published).

There is a continuum from these early charts through to the work of Henry Gantt (who is falsely accredited with developing ‘project management’ and ‘bar charts’) some 200 years later (for more on this see: The Origins of Bar Charting).

The most sophisticated of Gantt’s charts described in ‘The Gantt chart a working tool of management’ (Wallace Clark, 1923) shows slippage or acceleration on the overall target production for one batch of parts on one machine, but again this work does not extend to predicting the completion date for the work, or a related set of activities.

From a measurement perspective, the concept of ‘piece rates’ can be traced back to the 16th century (the phrase ‘piece work’ first appears in writing around the year 1549). Piece work requires measurement of performance to calculate a workers pay and record keeping. However, whilst there is ample evidence of people being measured and paid this way for more then 400 years, there is little indication of this information being used to predict outcomes.

Measuring performance was integral to Taylor’s scientific management and the work of Henry Gantt, Chapter 3 of Gantt’s ‘Work Wages & Profits’ focuses on incentives and bonus payments for production work in machine shops. Foremen and worker are to be paid a bonus if they achieve the target production time for a ‘piece’ of work. The bonuses are calculated after the event and nothing in work wages and profits refers to any form or predictive scheduling beyond the usual planning needed for machine loadings. Gantt’s work is the most advanced of any of the options discussed to date, but all of his charts are focused on highlighting problems so that management action could be directed to resolving the problem.

In short, nothing in the documented practice of accounting, ‘bar charting’, or piece rates, or Gantt’s motivational bonuses, were designed to predict the completion date of the work or it finals cost based on performance to date. All of these processes, including Gantt’s, were focused on solid planning and then working to achieve the plan by eliminating problems that caused slippage to make sure the work was accomplished in accordance with the plan (reactive management).

Whilst there would have been very little effort required to take the actual, planned or estimated production rates (minutes per unit) and divide that into the lot (scope of work) to predict when the production lot is going to be finished, no one seems to have taken this step. The start of predictive calculations does not seem to have emerged until operational research people started playing around with the concepts during WW2 (1940s).

Predictive time focused planning emerged at some time in the late 1940s or early 1950s with the development of linear programming in association with OR, which in turn morphed in CPM , PERT, MPM and a number of similar techniques all around the same time in the UK, Europe and the USA. Prior to the 1950s the focus was on ‘how far behind’ is any element of the work; the advent of network based scheduling allowed a process for predicting completion to be developed. Kelley and Walker’s 1959 paper is very clear on this (see Annex in A Brief History of Scheduling). From these time management foundations, PERT Cost emerged, then C/SCSC which in turn grew into EVM and more recently Earned Schedule (see: Predicting Completion).

Today, project controls are expected to predict cost and time outcomes for each project and in both business and government the expectation of forward predictions of profits, incomes and expenditures are normal.

The question posed by this blog is that given the fact astronomers were predicting celestial events from 1000 BC or earlier; and some of the charts and risk assessments we use today were available from at least the 17th century if not earlier, were these concepts used by managers to predict work outcomes?  Or did all of this emerge in the last 60 years??

More precisely, is there documented evidence of someone using current performance to update a plan and predict cost, time or other outcomes before the 1950s?

The evidence I have found to date that suggests predictions are very much a development of the last 60 years is freely available at: http://www.mosaicprojects.com.au/PM-History.html. I would be delighted to be proved wrong!

A History of Scheduling – 2nd Edition

BC#06One of my major papers, ‘A Brief History of Scheduling’ has been updated and republished  in the August edition of PM World Journal, the free online publication devoted to knowledge creation and sharing, and continuous learning in the field of modern program and project management.  To see the published article and sign-up for you free monthly journal see:  http://pmworldjournal.net/article/a-brief-history-of-scheduling-back-to-the-future/

This paper is one of a series looking at the origins of project management. the full set of papers can be accessed at: http://www.mosaicprojects.com.au/PM-History.html

The numbers in your calendar

PMWJ-CoverHave you ever consider the odd collection of numbers that make up the standard western calendar, 60 seconds in a minute, 60 minutes in an hour, 24 hours in a day and varying numbers of days in the months and years. The origins of some of these numbers and the basis of the modern calendar go back over 6000 years.

The origins of the different numbers and how they became the modern calendar is told in my featured paper published in the July edition of PM World Journal.  To read the paper and sign up for the free monthly e-Journal go to: http://pmworldjournal.net/article/the-origins-of-the-coordinated-universal-time-utc-calendar/

For more papers on the history of project management see:  http://www.mosaicprojects.com.au/PM-History.html

The Origins of Project Management

Based on Lynda’s analysis of ‘stakeholder’ using the new Google Ngram Viewer (see: Lynda’s post), I thought I would compare ‘stakeholder’ with ‘Project Management’.

Lynda’s Stakeholder graph:

The Ngram for Stakeholder

My graph of Project Management to the same dimensions:

The Ngram for Project Management

Comparing the two charts suggests ‘stakeholder management’ is a growing social phenomenon whereas ‘project management’ has reached a plateau, possibly suggesting it is a mature business function. Comparing the raw numbers, ‘stakeholder management’ has a very long way to go to catch up with ‘project management’ in terms of the amount of writing about the subject suggesting it will be an expanding area of interest for many years to come.

Interestingly, the start of the steady rise in interest in ‘project management’ from around 1960 fully supports the hypothesis in my paper The Origins of Modern Project Management that the spread of project management was directly linked to the development of CPM scheduling. The original work on CPM was done in 1957!

To explore the Ngram Viewer yourself, see: http://books.google.com/ngrams/

Project Planning and Scheduling

The Guide to Good Practice in the Management of Time in Complex Projects (The Guide)  will be published at the end of this year. One of he key messages in The Guide is the need to separate planning from scheduling.

Project planning focuses on creating the project development strategy. It requires experience, vocabulary, communication and imagination and, at its highest level, provides the formula for the logistic strategy for the project construction. Project planning involves decisions concerning:

  • the overall strategy of how the work process is to be broken down for control;
  • how the control is to be managed;
  • what methods are to be used for design, procurement and delivery;
  • the strategy for subcontracting and procurement;
  • the interface between the various participants;
  • the zones of operation and their interface;
  • maximising efficiency of the project strategy with respect to cost and time;
  • risk and opportunity management;
  • the design for the schedule and its reports/communication plan.

Scheduling is a mixture of art and science to create the project manager’s time-allocation tool within the chosen software. It involves the interpretation of the results of project planning to ascertain, amongst other things, the start and finish dates of activities, their sequence and the required resources.

It is not good practice to plan the work whilst attempting to schedule it. Starting to develop the schedule before planning the project is unlikely to produce a satisfactory project-planning solution or an effective schedule.

This is not a new idea! James Kelley and Morgan Walker, the inventors of the Critical Path Method of scheduling in the very first paper published on the subject had the following to say:

A characteristic of contemporary project scheduling is the over-simplification which stems from the inability of unaided human beings to cope with sheer complexity. Even though we know that a detailed plan is necessary, we also know that management need only act when deviations from the plan occur. To resolve this situation we undertook to develop a technique that would be very simple but yet rigorous in application. One of the difficulties in the traditional approach is that planning and scheduling are carried on simultaneously. Our first step was to separate the functions of planning from scheduling.

This is an extract from the paper entitled Critical Path Planning and Scheduling delivered to the Eastern Joint Computer Conference in March 1959, by Kelley and Walker less then 2 years after they had invented CPM. Why is it 50 years later so many planners continue to ignore the wisdom learned from past projects and focus on entering data into computers before they have worked out the optimum way to deliver the project?

For more on the history of scheduling and an abstract of the Kelley and Walker paper see: A Brief History of Scheduling

PM History papers updated

Working on my paper for PMOZ 2010, Seeing the Road Ahead – the challenge of communicating schedule data  has required me to re-visit two key papers and augment them with new information and materials discovered in the last few years.

A Brief History of Scheduling – Back to the Future has had quite a lot of new materials incorporated. I am now confident this paper accurately lays out the development of scheduling and in particular, the origins of PERT and CPM.

The Origins of Modern Project Management  has had a few new footnotes included an links the development of modern project management to its roots the the spread of scheduling in the early 1960s.

Both updated papers are available for downloading and I have most of the reference materials available for anyone interested in further research into these topics.

The PMOZ paper will be available after publication in a couple of weeks. For more on the PMOZ conference see: http://www.pmoz.com.au/