What is the term for an activity that Cannot be deferred without affecting the project completion date or another activity start date?

What do you want to do?

• Add a constraint for a task

  Inhaltsverzeichnis Show

  • What do you want to do?
  • Add a constraint for a task
  • Remove a constraint
  • Available constraints
  • Task constraints vs. task dependencies
  • What do you want to do?
  • About constraints
  • Set the start and finish dates for a task
  • Set a deadline date for a task
  • Change the constraint type for a task
  • Make constraint changes by using the Project Guide
  • Make constraint changes in the Task Information dialog box
  • Make constraint changes in the Constraint Dates table
  • What is the time by which the completion of an activity can be delayed without affecting the start of succeeding activities?
  • What is the duration by which an activity can be delayed without delaying the completion of the project?
  • What is the time by which the completion of an activity can be delayed?
  • What is the amount of time that a task can be delayed without affecting the subsequent tasks?

• Remove a constraint

• Available constraints

• Task constraints vs. task dependencies

Add a constraint for a task

If you have an unavoidable constraint, such as an event date, pick the constraint type as well as the date:

1. On the Gantt Chart task list, double-click the task.

2. Click the Advanced tab.

3. Pick an option from the Constraint type list.

4. If you pick a constraint other than As Late As Possible or As Soon As Possible, add a date to the Constraint date box.

   

Project management tip    Let Project do what it does best — schedule your project. Set task durations yourself and create links between tasks, and then Project will calculate the task start and finish dates.

Remove a constraint

You can’t technically remove a constraint, but you can reset it to the default value, tying it to other tasks rather than to a specific date.

1. On the Gantt Chart task list, double-click the task.

2. Click the Advanced tab.

3. In the Constraint type list, pick one of these options:

   • If your project is scheduled from the finish date, choose As Late As Possible.

   • If your project is scheduled from the start date, choose As Soon As Possible.

Available constraints

With Project, you can add eight different constraints to tasks. Those constraints come in three flavors:

• Flexible constraints, which don’t tie a task to a specific date.

• Semi-flexible constraints, which include earliest start dates or latest finish dates.

• Inflexible constraints, which have specific start or finish dates.

Task constraints vs. task dependencies

It’s easy to confuse task constraints (restrictions on when a task can start or finish) with task dependencies (links that show a relationship between tasks).

If you’re looking for details on dependencies, see Link tasks in a project.

What do you want to do?

• About constraints

• Set the start and finish dates for a task

• Set a deadline date for a task

• Change the constraint type for a task

• Make constraint changes by using the Project Guide

• Make constraint changes in the Task Information dialog box

• Make constraint changes in the Constraint Dates table

About constraints

There are three types of constraints:

• Flexible constraints do not have specific dates associated with them. Setting these constraints allows you to start tasks as early as possible or as late as possible, with the task ending before the project finish, given other constraints and task dependencies in the schedule.

• Semi-flexible constraints require an associated date that controls the earliest or latest start or finish date for a task. These constraints allow a task to finish at any time, as long as it meets the start or finish deadline.

• Inflexible constraints require an associated date that controls the start or finish date of the task. These constraints are useful when you need to make your schedule take into account external factors, such as the availability of equipment or resources, deadlines, contract milestones, and start and finish dates.

The following table lists the constraints provided in Project.

If you manually enter a start date or a finish date for a task, Project changes the constraint type for that task to Start No Earlier Than (SNET) or Finish No Earlier Than (FNET). These semi-flexible constraint types force the task to start or end on the specified date regardless of subsequent changes that would otherwise affect the task's place in the overall project plan.

For optimal scheduling flexibility, we recommend that you allow Project to use flexible constraints to calculate the start and finish dates for tasks based on the durations and task dependencies that you enter. Only if you have unavoidable constraints, such as an event date that cannot be moved, should you consider setting a constraint for a task manually.

Why?

Constraining a task that is dependent on another task can produce unwanted results, as illustrated in the following example:

The task "Pour foundation" is linked so that it starts as soon as "Dig hole" finishes. "Dig hole" is supposed to happen on the 10th. If you enter an inflexible constraint that forces "Pour foundation" to start on the 10th and then "Dig hole" finishes early, Project will not be able to take advantage of the early finish and move "Pour foundation" to start earlier.

Rather than setting specific dates for a task, consider assigning an As Soon As Possible (ASAP) constraint and enter a deadline for the task. Entering a deadline causes Project to display a deadline marker in the Gantt Chart view, and an indicator alerts you when the task's finish date moves past the deadline.

Set the start and finish dates for a task

For optimal scheduling flexibility, we recommend that you allow Project to calculate the start and finish dates for tasks based on the durations and task dependencies that you enter. However, if you have unavoidable constraints, such as an event date, you can set a specific start or finish date for a task.

1. On the View menu, click Gantt Chart.

2. Click the task that you are scheduling, and then click Task Information

   
   .

3. Click the Advanced tab.

4. Select a constraint type from the Constraint type list.

5. If you select a constraint other than As Late As Possible or As Soon As Possible, type a constraint date in the Constraint date box, or select a date from the calendar.

Notes: 

• When you schedule your project from a start date and type a date in the Start field of a task (or drag a Gantt bar to change the start date), Project sets a Start No Earlier Than (SNET) constraint for that task. If you type a date in the Finish field of a task, Project automatically sets a Finish No Earlier Than (FNET) constraint.

• Project 2007 starts new tasks on the project start date by default, but you can specify that new tasks start on the current date instead of the project start date. Choose Tools > Options > Schedule, and then in the Scheduling options section, select Start on Current Date in the New tasks list.

If you are having trouble with your task constraints, you may find the information in the following sections helpful.

Set a deadline date for a task

You can set a deadline date for a task to keep track of its finish date without locking the schedule with an inflexible constraint. Project updates the schedule as needed, keeps track of deadline dates, and shows a symbol in the indicator column if a task finishes after its deadline.

To set a deadline date for a task:

1. On the View menu, click Gantt Chart.

2. Click the task that you are assigning a deadline.

3. Click Task Information

   
   , and then click the Advanced tab.

4. Enter the deadline date in the Deadline box.

   Tip: If you decide later that you no longer want the deadline set for this task, you can remove the deadline by clearing the Deadline box.

5. Click OK to save the deadline. A green arrow appears next to the bar for the task in the Gantt Chart view. Project will not notify you if a deadline date is passed.

Note: When a task slips past its deadline date, Project calculates the negative slack for that task. For example, if a task finishes a day later than it was scheduled to finish, it displays a total slack of -1d.

Change the constraint type for a task

You can change the constraint type for a task in the Project Guide, the Task Information dialog box, or the Constraint Dates table.

Make constraint changes by using the Project Guide

1. On the Project Guide toolbar, click Tasks .

2. On the Tasks pane, click Set deadlines and constrain tasks.

3. Do one of the following:

   • To select a single task, click the task name.

   • To select more than one task, hold down CTRL and click each task name.

   • To select all of the tasks in your project, click Select All.

4. Under Constrain a task, select the constraint type that you want to use for the selected task or tasks.

5. Click Done.

Make constraint changes in the Task Information dialog box

1. Click the task that has the constraint, and then click Task Information

   
   .

2. On the Advanced tab, review or change the constraint type.

Note: Task constraints are also clearly marked in the indicator column with a constraint symbol (either or ). Rest the pointer on the constraint indicator to see the constraint type and date.

Make constraint changes in the Constraint Dates table

1. On the View menu, click More Views.

2. In the Views list, click Task Sheet, and then click Apply.

3. On the View menu, point to Table, and then click More Tables.

4. Click Task.

5. In the Tables list, click Constraint Dates, and then click Apply.

   The task sheet changes to show the Constraint Dates table, which shows the task name, duration, and constraint type for all constraints (including As Soon As Possible), and the constraint date, if applicable.

6. Do either or both of the following:

   • To change the type of a constraint, click the arrow in the Constraint Type field, and then click the constraint type that you want.

   • To change the date of a constraint, in the Constraint Date field, type or select the date that you want.

     If you change a constraint to As Soon As Possible (ASAP) or As Late As Possible (ALAP), the Constraint Date field shows NA.