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I have been thinking about the value of incorporating resources into schedules for some time. At one level it’s not too hard to do but is it useful?

From one aspect, it is impossible to schedule at any level without the active consideration of resources. Resources do the work in a given time and changing either the quality or quantity of the resource has some inevitable impact on the duration of the work. Consequently, it is critical to know the resource assumptions used in planning to validate the schedule and more importantly understand deviations from the plan during the execution of the work.

Generally what I mean by term ‘considered’ is the basic need to know the resources needed to undertake the work on every activity:

  • At the feasibility stage big picture tied to the strategy for the project.
  • At the contract stage to determine which tasks are the responsibilities of what contractor/subcontractor.
  • At the weekly level, the supervisors need to know who is working where and when.


These decisions also need to be recorded and monitored. How much detail is recorded in the scheduling tool and what scheduling functions are used though is an altogether different question – this I refer to as ‘quantitative’ resource analysis.

Consideration is not the same as quantitative analysis within a scheduling tool. Quantitative resource analysis requires answers, or assumptions to be made, about a range of uncertain issues. Some of the nearly insoluble questions include:

  1. There is no direct ‘straight line’ correlation between resource quantities and either task or project durations – there is a complex ‘J’ curve relationship and in some circumstances a negative correlation. For more on this see: The Cost of Time or for a more learned approach, The Mythical Man Month by Frederick P. Brooks Jr. originally published in 1975.
  2. It is nearly impossible to define the skill levels of unknown people who will be employed on a project at some time in the future but we know a skilled worker can be far more productive than an unskilled worker. The skill of the worker changes the production rates and consequently the durations.
  3. The final unknowable is the degree of motivation/moral of the people at some point in the future – a highly motivated team will always accomplish more than a ‘business as usual’ team and both more than a de-motivated workforce. Therefore the question of management and more importantly leadership also influence resource performance and therefore durations.


These unanswerable questions are complicated by the fact all scheduling software fails to optimally level resources. Basically the tools get it wrong; the only question is how wrong: some are not too bad others unmitigated disasters. Resource scheduling needs both knowledge and common sense – no software applies common sense yet. But we have to plan resources – they need working space, accommodation, etc. And resources are the source of all cost expended on the project!

Another really interesting factor is the emerging understanding of the interaction between the schedule and the behavior of people. IF the people believe the schedule represents a realistic approach to their work, they will (and do) modify their behaviors to conform to the schedule to be seen as successful. Obviously if resources are included in the schedule it is far more credible than if they are not. This was touched on in Scheduling in the Age of Complexity (read from p19 – the rest is not relevant and it’s a horribly long paper).

So in summary I would suggest, consideration of resources is critical, as is having some form of method statement; together they dictate the planned durations of the work.

However, whilst using scheduling tools to calculate and level resource demands is useful, and can help gain valuable insights, you need real skill on the part of the scheduler and the right tools to achieve sensible results. Regardless of the skills of the planner, KISS (Keep It Sweet and Simple) is an important aspect of effective resource planning. It is only useful to planning resource requirements at a level of detail that is appropriate for real management needs. But the basic issues remain; you cannot rely on a scheduling tool to optimize the duration of a resource leveled schedule.

We use a basic network in our Scheduling courses that very few software tools get ‘right’ and optimize the project outcome. The answer to achieving the shortest overall duration is starting the critical resource (Resource 3) as soon as possible. To achieve this Resource 2 has to focus 100% on completing Task B as quickly as possible BUT, Task C is on the Time Analysis critical path not Task B and 99% of the time software picks C to start before B delaying the overall project completion.

This is not a new problem, a paper by Kastor and Sirakoulis in the International Journal of Project Management, Vol 27, Issue 5 (July, 2009) p493 has the results of a series of tests – Primavera P6 achieved a duration of 709, Microsoft Project 744 and Open Workbench 863.

When Kastor and Sirakoulis adjusted the resource leveling settings in P6 and its results were 709, 744, 823, 893 – a huge range of variation and the best option (P6) was still some 46% longer than the time analysis result. Other analysis reported in the 1970s and 80s showed similar variability of outcomes.

As Prof. George Box stated – All models are wrong, some are useful… the important question is how wrong does the model have to be before it is no longer be useful.

Computer driven resource schedules are never optimum, done well they are close enough to be useful (but this needs a good operator plus a good tool). And good scheduling practice requires knowing when near enough is good enough so that you can use the insights and knowledge gained to get on with running the project. Remembering even the most perfectly balanced resource schedule will fall out of balance at the first update…..

My feeling is the value of the process to the development of a realistic and achievable schedule depends on the circumstances of the project.

  • Probably the biggest determinant of the value of quantitative resource analysis is the ease of adding to or reducing the resource pool. If this is easy, rudimentary quantitative analysis is all that’s needed, if any. If it is difficult to quickly change the resource pool far more rigor is required (eg, developing remote area mine sites in Australia). The quantitative analysis will still be ‘wrong’ but it is important to reduce the level error as much as possible.
  • The second consideration is time; detail resource scheduling is only viable for a few weeks into the future where you have a reasonable insight to the actual people available for the work. Further out, more general approaches are warranted applying techniques such as Schedule Density


The ultimate solution is more viable scheduling tools that are capable of proper resource optimization; these are beginning to emerge and are the focus of my paper Resource optimisation - a new paradigm for project scheduling, it is still a work in progress but there has been a lot of useful feedback.

What is your take on resource scheduling?

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Comment by Patrick Weaver on October 10, 2012 at 6:18pm

The fundamental problem (recognised 60 years ago) is the two fixtures in a project are the work defined as ‘activities’ and the resources allocated to the project.  Durations and to a lesser extent sequence are variables.  The 60 year old dumbed down CPM that Kelley and Walker were forced to adopt because of computer processing limitations used fixed durations based on a set resource allocation (computers are millions of times more powerful now).

An effective resource optimisation tool will be easy to use but will also use parameterised optimisation to finesse durations and sequence based on resource capabilities. There are a couple of tools available that are starting down this path.

Comment by Andrew Rogoff on October 10, 2012 at 5:49pm

You're welcome Patrick. I think the problem we are solving is only one aspect of the problem you have outlined. But, for all of our customers, Resource Guru provides them with a good solution for that particular aspect. They enjoy the fact that they can delete their clunky spreadsheets and avoid using complex software that can only be used by those who take the time to wade through a huge training manual. Furthermore, they like the fact that our tool is collaborative and schedules can instantly be communicated on resources' dashboards.

Resource Guru is not a static product - it is constantly evolving - and, in the future, we will be looking into solving some of the other problems you mention. Thanks for your thoughts.

Comment by Patrick Weaver on October 10, 2012 at 4:41pm

Thanks for the commercial Andrew – yet another piece of software that does not solve ANY of the problems outlined in my post – when are you developers going to actually deal with the problems???  60 years ago Kelley and Walker had a good part of the solution in the original CPM model, this was dumbed down to work on the computers available in the late 1950s and virtually no-one has done anything to advance the issues from that time forward. The arbitrary allocation of resources to fixed duration activities only works on very small projects for a very few weeks into the future.


For a more in-dept look at the problem see: Resource optimisation - a new paradigm for project scheduling at

Comment by Andrew Rogoff on October 10, 2012 at 9:38am

Hi Patrick - interesting article. Resource scheduling is a very tricky problem. We've designed a simple, intuitive web app called Resource Guru to try and alleviate some of the problems - We've got some great companies on board and I would love to hear your thoughts. You can contact me through the site.

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