Volume of work and Productivity

Volume of work and Productivity

There are two main approaches used to estimate project work: duration-based and volume-based.

Often schedules are developed with a duration-based approach, mostly due to planning tools limitations.

An alternative, much more powerful approach is based on the volume of work and productivity of assigned resources. Volume-based planning is an intuitive and easy method.

Activity volume is used as initial activity information instead of duration.

Activity volume can be measured in meters, tons, story points, planned work hours, percentages, pages or any other units.

Resource productivity is defined in volume units per hour.

Activity durations are calculated as the volume of work divided by assigned resource productivities.

Example 1
A worker needs to dig a 100m trench. If his productivity is 5m/h, the duration of this activity would be 20 hours.

Example 2

A bulldozer is needed to push 200 m3 of sand. We have two resources that could be used for this work: a powerful bulldozer 1 with a productivity of 20 m3/h and an older model bulldozer 2 with a productivity of 10 m3/h.

The duration of the activity will be 10h or 20h, depending on which bulldozer is assigned to this activity.

The assignment is likely to depend on:

  • other works need to be completed by bulldozers;
  • whether this activity is on a resource critical path or not. If not, we may prefer a less productive/cheaper bulldozer.

Volume-based planning has many advantages:

Projects are often planned (especially in construction and manufacturing) based on the federal, local, industrial or corporate norms and standards. These standards usually refer to resource productivity on the certain activity types per unit of activity volume (costs and materials as well). These norms could be used as a base for planning.

Unlike activity duration activity volume (scope) is a more stable and reliable activity characteristic as it does not depend on assigned resources.

Usually, it is much easier to measure the volume of work to understand activity progress.

Resource Supply
When resource supply is changed, activity durations could be automatically adjusted.

What-if analysis
It is much easier to complete a What-if analysis and find an optimal resource demand.

Risk analysis
If the volume of work is uncertain, the volume range could be used as a base for quantitative risk analysis. The same for productivity. Uncertainties in the productivity of resources also could be taken into account.

Productivity-based scheduling is realised in Spider Project and usually is the preferred way to manage project work.

See how it works in Spider Project:

Julia Lyaschenko

PMO | Program Planning & Delivery Specialist | PRINCE2© Practitioner | SAFe© Agilist (SA)

Project Teams Assignment

Project Teams Assignment

One of the fundamental problems in project delivery is that scheduling tools are not able to simulate real-life work scenarios correctly.

Resource Assignments

In project schedules there are often some activities that require assignment of more than one  resource. In some situations activities could be performed only when all resources are available. In other scenarios activities could commence as soon as any resource is available.

Scenario 1

In this scenario we have two resources assigned to complete work. Unless both of these resources are available the work can not be done.


We need to move tables. There are two workers required to carry a table. This work can start only when both resources are available.

The activity will not be completed quicker even if a third worker would be available for this task.

Scenario 2

In the second scenario, we also have two resources assigned. However, the nature of this activity allows them to work independently one from another. The work can start as soon as one of the resources is available.


We are moving chairs. Only one person is needed to carry a chair. The assigned workers can move the chairs independently one from another. Any available worker could start moving chairs. When (and if) the second resource is available, both resources will work together and complete the work faster.

Similarly to the previous example, the duration of this work is also dependant on the availability of assigned resources. However, a different type of logic needs to be applied to calculate the duration of this activity.

The activity can be completed quicker if a third worker is also available.


Scenario 3

Some activities require more complex simulation when “all” and “any” types of logic need to be combined.

Scenario 3 demonstrates that you can actually combine scenarios 1 and 2 when work could be done by any group of resources.


Some projects use shifts. An activity requires two workers and can be started in any shift. If not completed, two workers from another shift would continue the work.

Majority of scheduling tools really struggle to calculate durations of these scenarios correctly.

Spider Project has a special feature, called “Teams“, that allows the simulation of all possible scenarios of resource assignments.

Team is a group of resources working on an activity together.

The team may include individual resources, multi-resources (crews) and skills (resource pools).

See how Teams Assignments work in Spider Project:


Julia Lyaschenko

PMO | Program Planning & Delivery Specialist | PRINCE2© Practitioner | SAFe© Agilist (SA)

Multi-Resource (Crew) Assignment

Multi-Resource (Crew) Assignment

Resource Assignments by Multi-Resource (Crew)

In some situations, a set of activities is performed by a stable group when multiple resources work together. We could assign each resource from this group to each activity individually.

However, it is much easier to assign these resources as a whole group at once. This could be done via multi-resource assignment.

Multi-Resource is a settled group of resources that work together (e.g. a team, a crew, a car and a driver, etc.).

This approach has several advantages:

  • Faster schedule development;
  • Reduction of errors in resource assignment;
  • Schedule updates are significantly simplified.

At any moment when there is a change to participants in a multi-resource, we could apply this change in the multi-resource. Then this change will be applied to all remaining multi-resource assignments at once.

See how Multi-Resource Assignments work in Spider Project:

Julia Lyaschenko

PMO | Program Planning & Delivery Specialist | PRINCE2© Practitioner | SAFe© Agilist (SA)

Resource Skills Assignments

Resource Skills Assignments

Resource Assignments by Skills (Pools)

In real-life scenarios, it is quite common that we don’t know which resources exactly would be available when the activity is ready for execution. It might depend on work priorities, resources availability, their productivity and cost.

But what we know most of the time is that what kind of resource skill would be needed for the required activity. 

Resource Skills are the groups of interchangeable resources.

Resources belong to the same skill set if they can do the same type of work. They might have different costs and productivities but can still replace one another to get the work done.

Another term used for skills is a pool of resources.

Skills are usually assigned when it is not clear what resources will be available at the moment when an activity becomes ready for execution.

A resource may have more than one skill and may belong to different pools.

At any moment when there are changes in skills pool participants, these changes can be easily applied to all future skills assignments.

See how Resource Skills Assignments work in Spider Project:

Julia Lyaschenko

PMO | Program Planning & Delivery Specialist | PRINCE2© Practitioner | SAFe© Agilist (SA)

Is Missing Logic an illusion of schedule quality?

Is Missing Logic an illusion of schedule quality?

Scheduling consultants often mention “Missing Logic” as an obvious schedule quality check.
I believe it is not as obvious as it seems. This check may create an illusion of good quality of dependency data and hide critical issue(s) that may cause project delay.

The rule of thumb is “Each activity, except first and last activities, must have a predecessor and successor”. It is logical to have a metric that verifies if this rule is followed. This metric is known as the “Missing Logic” or “Open ends” metric. If a schedule has open-end activities, it requires  attention.

However, if there are no activities without a predecessor and a successor, it DOES NOT mean there are no “lost” or “broken” dependencies in the schedule.

Even more, the “lost” dependency may impact the critical path and reduce the duration of the schedule, but the “open ends” metric still would be “Green”. It creates an illusion that the schedule doesn’t have issues with dependencies and no additional check is required. The “lost” and “broken” dependencies would not be identified until it is too late, and the project delivery dates are impacted.

Broken Dependency

A“broken” dependency is a dependency with incorrect characteristics (type, lag, ect).

Path Convergence & Path Divergence

Any schedule is likely to have activities with multiple predecessors and/or successors. It is possible that after a critical dependency has been removed, the schedule still doesn’t have open ends activities.

Path Convergence
A relationship in which a scheduled activity has more than one predecessor.

Path Divergence
A relationship in which a scheduled activity has more than one successor.

Original schedule:                                                                                                         

Critical Path: A B D E G

“Missing Logic” check: Green

Then a scheduler by mistake deleted one critical Dependency between D and E activities. Now the schedule has a new critical path and shorter duration, but the “Missing Logic” metric is still “Green” as all activities (except first and last) still don’t have open ends.

This example shows that we need another approach to manage the quality of dependencies.

The only way to check the quality of dependencies is to compare the list of dependencies against Corporate Norms or any other reliable set of dependencies, for example, in a baseline schedule.

As Primavera and MS Project users don’t have direct access to a list of dependencies, one of the options could be to load the schedule into the tool that has this capability.

Spider Project provides access to a list of all dependencies with all dependency characteristics: predecessor and successor codes and title, dependency type, lag, lag units, lag type, lag calendar, etc. Dependency quality analysis could be performed within the tool, or dependencies could be exported to Excel or BI tools.


Missing Logic” metric is a required but not sufficient metric. It may create an illusion that the schedule dependencies are in good shape.

Dependency quality analysis have to be performed against reliable dependency data and incorporate analysis of both “lost” and “broken” dependencies.

Alex Lyaschenko

PMO | Portfolio Planning & Delivery | PMP | P3O Practitioner | AgilePM Practitioner | Six Sigma