Working with nonlinear allocations and resource curves

In the case of simple resource and cost allocations, the effort, quantity or cost runs evenly throughout the duration of the allocation, meaning that the amount of effort, quantity or cost per hour, or per day, is the same. Such allocations are referred to as "linear" allocations, because the cumulative effort, quantity or cost can be represented by a straight line.

Resource curves

In some cases, the effort, quantity or cost of an allocation may not be linear. You can reflect this in a project by assigning resource curves to resource or cost allocations in order to plan nonlinear assignment - assignments in which work or cost occurs sporadically, or at varying levels of effort, quantity or cost. A resource curve consists of a number of discrete rectangular segments - or 'points' - each of which defines a percentage of duration and a corresponding level of allocation. For example, if a resource curve has ten points, the first segment relates to the first 10% of an allocation's duration and defines the amount of allocation that relates to that segment. You can configure resource curves to accurately represent the varying levels of effort, quantity or cost across the duration of the allocations to which the resource curve is assigned.

You can configure resource curves to have any number of points between 2 and 50; the more points you give a resource curve, the more detail in which you can plan your effort, quantity or cost. You specify the percentage of allocation duration that is represented by each point in a resource curve.

For example, you may want to create a 'front-loaded' resource curve, in which effort, quantity or cost is greatest at the start of an allocation and tails off towards the end; you may want to create a 'back-loaded' resource curve, in which effort, quantity or cost is greatest at the end of an allocation; you may want to create a 'bell-shaped' resource curve, in which effort, quantity or cost is at its greatest around the middle of an allocation.

Resource curves define the same allocation profile for each allocation to which they are assigned, regardless of the allocation's duration. If the duration of an allocation changes, the allocation profile automatically shortens or lengthens accordingly.

Individual allocation profiles

In the case of permanent resource allocations, you can also specify that an allocation should use an individual allocation profile, which acts in a similar way to a resource curve but which applies to an individual allocation only. An allocation profile consists of a number of discrete segments, each of which defines a duration and a corresponding level of effort.

Using individual allocation profiles gives you very fine-grained control over the day-to-day assignments of individual resources. If you configure an allocation profile for a resource and decide that you want to apply it to other resources, you can create a resource curve based on the allocation profile.

Nonlinear allocations and resourcing logic

Applying a resource curve or an individual allocation profile to an allocation does not affect Asta Powerproject's resourcing logic. For a permanent resource allocation, for example, the following calculations apply to nonlinear allocations just as they do to linear allocations:

Allocation = Effort / Duration.
Effort = Duration x Allocation.
Duration - Effort / Allocation.

Where the effects of nonlinear allocations are visible

The effects of making an allocation nonlinear - whether by applying a resource curve or an individual allocation profile to it - are visible in the following areas:

Resource usage view - which is an excellent tool for viewing and editing the varying daily or weekly totals of nonlinear allocations. Note that using the resource usage view to edit nonlinear allocation values for individual days decreases or increases the total effort, quantity or cost of the allocation, while the duration remains the same.
Histograms - in which nonlinear allocations are depicted as a sequence of rectangles that define the distribution of effort, quantity or cost across the duration of the allocation.
The Properties dialogs of resource and cost allocations.
When displaying effort, quantity or cost in the spreadsheet in cells that are limited to a date range.

The resource leveller also takes account of nonlinear allocations of effort, as do Asta Powerproject's overallocation warnings.

Standard work and nonlinear allocations

If you use standard work to represent time that permanent resources are not available to work on project activities, do not apply individual allocation profiles to permanent resource allocations; the two do not work well together. If you want to plan nonlinear allocations in conjunction with standard work, use resource curves rather than individual allocation profiles.

How allocation is apportioned when you assign a resource curve to an allocation

Resource curves are defined in terms of percentages of duration and percentages of value. When you apply a resource curve to an allocation, the dates for each segment of the curve are calculated by multiplying the duration by the percentage. For example, consider a 10d permanent resource allocation with 75h of effort, to which a front-loaded resource curve is applied. The resource curve has 20 points, which means that each point corresponds to 5% of the duration - ie half a day of this particular resource allocation. The front-loaded resource curve has 10 points of 6.5% and 10 points of 3.5%.

Where the value of a point is 6.5, the effort is 75 x 0.065 = 4.875h. The half day has a duration of 3.75h, so the resulting allocation is 4.875 / 3.75 = 1.3. One day at this point of the resource curve contains 9.75h of effort.
Where the value of a point is 3.5, the effort is 75 x 0.035 = 2.625h. The half day has a duration of 3.75h, so the resulting allocation is 2.625 / 3.75 = 0.7. One day at this point of the resource curve contains 5.25h of effort.

This means that the 10d allocation consists of 5d with an allocation value of 1.3 and total effort of 48.75h, followed by 5d with an allocation value of 0.7 and total effort of 26.25h.

How progress is calculated on nonlinear allocations

When you mark progress against a task, its allocations are progressed in step. For example, if you mark a task as being 25% complete, its allocations are automatically marked as being 25% complete. If a task has a nonlinear allocation, the actual effort, quantity or cost is calculated according to the resource curve or individual allocation profile and the remaining effort, quantity or cost is redistributed according to the remaining part of the resource curve or allocation profile.

For example, consider a 10d permanent resource allocation with an allocation of 10, to which a triangular resource curve is applied.

If you mark the task as being 40% complete (ie 4d out of the 10d have been completed), the resource curve is used to calculate the effort to date: 32d.
If you record progress of 32d effort against the task, the resource curve is used to calculate the duration in which the effort took place: 4d.

Illustration

The resource curve used in the above example is illustrated below:

Example resource curve

Here, the result of applying the resource curve is best illustrated by using a histogram to display the effort to date. The following illustration shows the situation before progress is applied to the task:

A histogram displaying the effort to date of a 10d permanent resource allocation, with an allocation of 10

You can specify how effort, quantity or cost is distributed in completed sections when progress is applied to nonlinear allocations, using the Maintain allocation profiles on progress check box, on the Progress tab of the Options dialog:

If you select this check box, when you apply progress to a nonlinear allocation, the effort, quantity or cost in the completed section is distributed according to the resource curve or allocation profile that has been assigned to the allocation, and the profile on the Nonlinear Assignment tab of the Resource Properties dialog displays correct values for the completed section. This is illustrated below, where 40% progress has been recorded against the task:
If you clear this check box, when you apply progress to a nonlinear allocation, although the completed section contains the correct total planned effort, quantity or cost, the effort, quantity or cost is not distributed according to the resource curve or allocation profile; the completed section contains average values, and the profile on the Nonlinear Assignment tab of the Resource Properties dialog displays zero values for the completed section. This is illustrated below, where 40% progress has been recorded against the task:

If you use standard work to record time when resources are not available on project activities, you may still notice that hours are not distributed according to the resource curve or individual allocation profile when applying progress to nonlinear allocations, even with the Maintain allocation profiles on progress check box selected. This is because standard work is flattened when you record progress on allocations, so it is not possible to identify exactly when a period of standard work took place in a progressed section.

If you change the duration of, or delete, a completed section of a nonlinear allocation, the allocation profile is adjusted to reflect the new total duration of the allocation.

Increasing the effort of allocations with individual allocation profiles

If you increase the effort of a nonlinear allocation to which an individual allocation profile has been applied, the allocation is derived not from the average allocation, but from the allocation of the last value in the allocation profile; an additional value is added to the allocation profile to represent the additional effort.