As soon as you assign resources to automatically scheduled tasks, two new methods become available to you for controlling how tasks are scheduled: task types and effort-driven scheduling. Use these methods so that as you optimize the project plan to target the required finish date, budget, and scope (or respond to changes after project implementation is under way), automatic task and assignment scheduling happen the way you expect and the way that most closely models reality.
For automatically scheduled tasks to which resources have been assigned, when you change one of the following values, another of the three has to compensate for the change:
Assignment units. Reflect the number of resources assigned and to what extent—full time, part time, and so on. Adding or removing resources, or otherwise changing assignment units after the initial assignment, constitutes this type of change.
Work. The amount of time (hours, days, and so on) that resources are working on the assigned task.
Duration. The time span from the start to the finish of the task. Changing the duration naturally affects the finish date, although it can also affect the start date.
Assignment units, work, and duration are fundamental to how a task with assigned resources is scheduled. The three are interrelated and interdependent. It’s another triangle-type relationship. When you change one of the three, at least one of the others is affected. For example, by default, if you revise duration, work is recalculated. If you revise assignment units, duration is recalculated. This is based on the basic Project 2010 scheduling formula:
Duration * Units = Work
Whether duration, units, or work changes automatically to compensate for your change depends on the task type and whether the task is effort-driven.
Note
Along with the concept of effort-driven scheduling, the interrelationship between duration, units, and work is a major principle that drives how Project 2010 schedules your project. Commit this formula to memory, write it on a yellow sticky on your computer’s monitor, make it your screen saver marquee—anything to help you remember this concept as you work with your project.
So what are the task types? Think of the task type as the one anchor among the three elements of units, work, and duration. When you make a change, the task type dictates which of the three elements must remain fixed, and which of the other two can flex to accommodate the change. (See Figure 10-12.)
Figure 10-12. When you change one of the three elements, at least one of the others is affected, which changes your task or assignment scheduling.
Setting the task type for each task gives you control over how the schedule is affected when you change units, work, or duration.
The three task types are as follows:
Fixed Units
Fixed Work
Fixed Duration
Which task type you choose for your project default and change for individual tasks has to do with how you develop your project and the scheduling rules you have in mind as you set your task durations and assign your resources.
Because choosing task types is a form of specifying how tasks are automatically scheduled, task types apply only to automatically scheduled tasks.
Before you dive deeper into a discussion of which task types are right for your schedule, you need to understand effort-driven scheduling.
As its name indicates, effort-driven scheduling dictates that as more resources are added to a task, there is less work for each resource to perform, although the total work to be done by all assigned resources remains constant. This is the “many hands make light work” principle.
Likewise, if resources are removed from a task, each remaining resource must do more work—again, with the total work for all assigned resources remaining constant.
The results of effort-driven scheduling operate in conjunction with the task type, as follows:
For an effort-driven, fixed-units task, adding resources decreases the duration.
For a fixed-work task, adding resources also decreases the duration. By its nature, a fixed-work task is always effort-driven.
For an effort-driven, fixed-duration task, adding resources decreases the work assigned to each resource.
By default, effort-driven scheduling is turned off for all tasks. This is a change from previous versions of Microsoft Project, in which effort-driven scheduling was the default.
This new default gives you more control over your schedule. It’s an advantage if the majority of your automatically scheduled tasks should not have their duration, and by extension their finish dates, change when you add or remove assigned resources.
For example, you might have a 4-day architectural drawing review task as part of a construction project. You want all resources assigned to have 4 days to review the drawings. Suppose that you realize later that you forgot a resource who also needs to review the drawings. When you add this resource to the task, you wouldn’t want the duration to be reduced—you still want everyone to have 4 days. It isn’t the type of task that can be completed more quickly if more resources are added. For these types of tasks, having effort-driven scheduling turned off is best.
On the other hand, suppose that in the same construction project you have a painter assigned to paint the building in 4 weeks. You determine that you need the building to be painted in 2 weeks. You make this an effort-driven task, and when you add a second painter, the task duration is reduced to 2 weeks. In many cases, the primary reason for adding resources to a task is to bring in its finish date.
The upshot is to look at the nature of the task to determine whether it is effort-driven or not, and then set the task accordingly.
To turn on effort-driven scheduling for selected tasks, follow these steps:
In the Gantt Chart or other task sheet, click the task for which you want to turn on effort-driven scheduling.
If you want to turn on effort-driven scheduling for several tasks at one time, click the first task, hold down Ctrl, and then click the other tasks.
On the Task tab, in the Properties group, click Information.
In the Task Information dialog box, click the Advanced tab.
Select the Effort Driven check box.
To turn on effort-driven scheduling for all new tasks in the current project plan:
On the File tab, click Options, and then click Schedule in the left pane.
Under Scheduling Options For This Project, select the New Tasks Are Effort Driven check box.
To turn on effort-driven scheduling for all new tasks in all project plans:
On the File tab, click Options, and then click Schedule in the left pane.
In the box next to Scheduling Options For This Project, click All New Projects.
Select the New Tasks Are Effort Driven check box.
When you assign a resource to a task, you specify the assignment units in the Units field of the Assign Resources dialog box. As shown in Figure 10-13, you can see the units listed in the chart area of the Gantt Chart. By default, the units appear with the resource name next to the Gantt bar if the units are anything other than 100%.
The Fixed Units task type dictates that the percentage of assignment units on an assignment should remain constant, regardless of changes to duration or work. This is the default task type because it’s the task type that fits the majority of project tasks. If you increase task duration, Project 2010 shouldn’t force you to find another resource or force a 50% resource to work 100% on the assignment.
Changes to a fixed-units task have the following results:
If you revise units, duration also changes, and work is unchanged.
If you revise work, duration also changes, and units are unchanged because they’re fixed.
If you revise the duration, work also changes, and units are unchanged because they’re fixed.
Set a task to the Fixed Units task type if the priority for the task is that its assignment units be constant unless you explicitly change them and if it’s okay for duration and work amounts to change. If this is the case for the majority of the tasks in your project, make Fixed Units the default task type for your project.
When you assign a resource to a task, the task’s duration is translated into work. You can see the amount of work in the Task Usage or Resource Usage view.
The Fixed Work task type dictates that the amount of work on an assignment should remain constant, regardless of changes to duration or units.
Changes to a fixed-work task have the following results:
If you revise units, duration also changes, and work is unchanged because it’s fixed.
If you revise work, duration also changes, and units are unchanged.
If you revise the duration, units also change, and work is unchanged because it’s fixed.
Set a task to the Fixed Work task type if the priority for the task is that its work amounts remain constant unless you explicitly change them, and if it’s okay for duration and assignment units to change. If this is the case for the majority of the tasks in your project, make Fixed Work the default task type for your project.
When you create a task, you specify the task’s duration in the Duration field of the Gantt Chart or other task sheet. The Gantt bar for the task is drawn according to the duration you set.
The Fixed Duration task type dictates that the task duration should remain constant, regardless of changes to units or work.
Changes to a fixed-duration task have the following results:
If you revise units, work also changes, and duration is unchanged because it’s fixed.
If you revise work, units also change, and duration is unchanged because it’s fixed.
If you revise the duration, work also changes, and units are unchanged.
Set a task to the Fixed Duration task type if the priority for the task is that its duration values remain constant unless you explicitly change them, and if it’s okay for work amounts and assignment units to change. If this is the case for the majority of the tasks in your project, make Fixed Duration the default task type for your project.
Table 10-1 clarifies how Project 2010 reacts when you make certain schedule changes to a task, according to a task’s task type or its manual scheduling mode.
Table 10-1. Task Types and Modes
Task type or mode | Add or remove resources (units) | Change assignment units | Change work | Change duration |
|---|---|---|---|---|
Fixed units (default) | Changed: Work Unchanged: Duration and units | Changed: Duration | Changed: Duration | Changed: Work |
Fixed units effort-driven | Changed: Work and duration | Changed: Duration | Changed: Duration | Changed: Work |
Fixed work effort-driven | Changed: Duration Unchanged: Work | Changed: Duration Unchanged: Work | Changed: Duration | Unchanged: Work |
Fixed duration | Unchanged: Duration, work, and units | Changed: Work Unchanged: Duration | Changed: Work Unchanged: Duration and units | Changed: Work |
Fixed duration effort-driven | Changed: Work Unchanged: Duration and units | Changed: Work Unchanged: Duration | Unchanged: Duration and units | Changed: Work |
Manually scheduled tasks | Changed: Work | Changed: Work | Unchanged: Duration | Changed: Work |
Manually unscheduled task (placeholder) | Changed: Work | Changed: Work | Unchanged: Duration | Changed: Work |
As you gain more experience working with Project 2010, you’ll see how the changes you make cause schedule recalculations, especially for your automatically scheduled tasks. Specifically, you’ll come to appreciate the power of using different task types in different situations. You’ll find that although the majority of your tasks are set at the default task type, you’ll have a handful of tasks that use different task types because they need to be scheduled differently.
By default, all tasks are Fixed Units. To change the task type for selected tasks, follow these steps:
In the Gantt Chart or other task sheet, click the task for which you want to change the task type.
If you want to change the task type for several tasks at one time, click the first task, hold down Ctrl, and then click the other tasks you want.
On the Task tab, in the Properties group, click Information.
In the Task Information dialog box, click the Advanced tab.
In the Task Type box, click the task type you want to apply to the selected tasks.
To set the default task type for all new tasks in this project plan, follow these steps:
On the File tab, click Options, and then click Schedule in the left pane.
Under Scheduling Options For This Project, in the Default Task Type box, click the task type you want to apply to all new tasks.
To set the default task type for all new tasks in all project plans:
On the File tab, click Options, and then click Schedule in the left pane.
In the box next to Scheduling Options For This Project, click All New Projects.
In the Default Task Type box, click the task type you want to apply to all new tasks in all new projects.