Working with resources
Resources are the people, equipment, machinery and materials needed to carry out tasks in a project. There are two types of resource:
- Permanent resources: resources that are not depleted by their use in a project. When one task has stopped using a permanent resource, the resource becomes available for other tasks to use. Employees, machinery and equipment are examples of permanent resources.
- Consumable resources: resources that are depleted by their use in a project. Once a consumable resource has been used by a task, it cannot be used again. Materials, components and utilities, such as concrete, bricks, water and electricity, are examples of consumable resources.
You must set up details of all the resources you want to use in a project, such as the resource name, its availability, working pattern and cost. You can assign a resource to as many tasks as you want. When you add a resource to a task, the cost of the resource is added to the cost of the task.
You can set up allocation groups to combine permanent and consumable resources that you often assign to tasks together into a single entity. For example, you could create an allocation group comprising an Engineer (a permanent resource) and metres of cable (a consumable resource). Then you can assign both resources to tasks at the same time by assigning the allocation group.
Once you have assigned resources to tasks, you can create resource histograms that show how many resources are being used at any one time and whether a resource is over or under-allocated.
The following resource histogram illustrates the allocation of a permanent resource over the duration of a project:
Resource modelling
When you estimate the duration of a task, you may know that it will take ten days to complete, no matter how many resources are assigned to it. Such tasks are duration-driven. Alternatively, you may know that two resources will have to work on a task until it is complete, regardless of time. Such tasks are resource-driven. When you assign resources to resource-driven tasks, you can control how the resource assignment is calculated when the duration of the task changes. This is known as resource modelling. You can model resources in the following ways:
- No resource modelling: if you do not use any form of resource modelling, a resource always works for the full duration of a task. For example, if you assign a resource to a task that is two days long, the resource also works for two days. If you increase the duration of the task to four days, the resource also works for four days.
- Fixed resource modelling: if you use fixed resource modelling, a resource always works for the initial duration of a task. For example, if you assign a resource to a task that is two days long, the resource also works for two days. If you increase the duration of the task to four days, the resource still only works for two days.
- Proportional resource modelling: if you use proportional resource modelling, the allocation of a resource is calculated in proportion to the duration of a task. For example, if you assign a resource to a task that requires two days' effort, the task duration is two days.
When using proportional resource modelling, if you increase the duration of the task to four days, you can recalculate the resource assignment in one of the following ways:
- Decrease the amount of resource assigned to the task, as the resource now has more time to complete the same amount of effort, so the two days' resource effort is spread over four days.
- Increase the amount of effort required for the task, as the same amount of resource working for longer means that more effort is required, so four days' resource effort is required.
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