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Chapter 6 - Tying Tasks to Specific DatesIntroduction Linked Tasks Can Be Flexible or Inflexible Types of Constraints Constrain a Task to Start or Finish On or Near a Specific Date Reso

Chapter 6 - Tying Tasks to Specific Dates

Introduction

Linked Tasks Can Be Flexible or Inflexible

Types of Constraints

Constrain a Task to Start or Finish On or Near a Specific Date

Resolve a Task Constraint Conflict

In most situations, you can schedule tasks to occur at the right time by listing them in logical order, linking them, and adding lead or lag time Performing these three actions gives your schedule maximum flexibility If a task starts earlier or later than planned, all the succeeding linked tasks begin earlier or later, too

Occasionally, a task must start or finish in relation to a specific date to successfully complete the project For example, the planner for the clockwork exhibit knows that the museum work crew won’t be available to paint the gallery walls until January 28, so the planner specifies that painting start no earlier than January 28 By doing

this, the planner has changed the constraint, tied to a specific date, to the painting task

Every task in Microsoft Project has a constraint applied to it If you don’t apply a constraint, a default constraint

is applied for you For example, the As Soon As Possible constraint, which is the default constraint, tells Microsoft Project to schedule a task to start on the earliest date possible, taking predecessor links, lag or lead time, and other scheduling factors into account Normally, you let Microsoft Project calculate the start and finish dates for a linked task, leaving it to recalculate these dates as the schedule changes

Linked Tasks Can Be Flexible or Inflexible

Constraints applied to linked tasks can be flexible or inflexible A flexible constraint allows a task’s start and

finish dates to be automatically recalculated when the dates of other tasks in the same linked sequence change Examples of flexible constraints are the As Soon As Possible constraint and the Start No Earlier Than constraint (which allows a task to start later only if you schedule your project from the project start date and not the project finish date)

Inflexible constraints tie a task to a specific date Typically, the dates for a task with an inflexible constraint don’t change when the dates of other tasks in the same linked sequence change These dates remain fixed Examples

of inflexible constraints are the Must Start On and Must Finish On constraints

Constrain a task if:

• The constraint reflects an actual time restriction in the real world

• The project will be penalized for not starting or finishing by a specific date

If a task doesn’t absolutely need to start or finish on or near a specific date, don’t apply an inflexible constraint When you apply inflexible constraints to tasks, you bypass the advantage of allowing Microsoft Project to

calculate task start and finish dates for you automatically as the schedule changes If a constraint is

unnecessary, change it

Keep in mind that constraints may become undesirable when you reschedule tasks For example, if you specify that a task must start on a specific date, but its predecessors actually take longer than planned, there might not

be enough time for the predecessors to finish before the constrained task is scheduled to start If a predecessor task ends up overlapping the constrained task, a resource assigned to both tasks might be overloaded with work

on the overlapping days On the other hand, if the predecessor tasks happen to start a week earlier than

planned, you might end up with a week of dead time in your schedule

Types of Constraints

Eight types of constraints are available in Microsoft Project By default, all tasks are assigned the As Soon As Possible constraint You can, however, choose the constraint that best meets a task’s start or finish

requirements

Most constraints are based on a date you specify, tying the start or finish of a

task to that date With As Soon As Possible and As Late As Possible

constraints, Microsoft Project can schedule tasks flexibly relative to the

predecessor and successor tasks

The following table lists the eight types of constraints, describes each type, and states when each type should

be used

As Soon As

Possible

(ASAP)

Starts the task as soon as possible based

on links to other tasks Allows schedule changes to start tasks earlier or later

Starting a task as soon as its links with predecessor tasks, if any, allow Do not enter a date with this constraint

As Late As

Possible

(ALAP)

Starts the task as late as possible based

on links to other tasks Allows schedule changes to start tasks earlier or later

Starting a task as late as possible without delaying the project end date or the finish date of a successor task Do not enter a date with this constraint

Finish No

Earlier Than

(FNET)

Finishes the task on or after the date you enter Allows schedule changes to finish tasks later

Tasks that perhaps can but shouldn’t finish before a specific date, such as the aging process for cheese Microsoft Project automatically assigns this constraint when you enter a task finish date

Start No

Earlier Than

(SNET)

Starts the task on or after the date you enter Allows schedule changes to start tasks later

Tasks that must start on or after a specific date Microsoft Project automatically assigns this constraint when you enter a task start date

Finish No

Later Than

(FNLT)

Finishes the task on or before the date you enter Allows schedule changes to move the finish date up to, but not beyond, the specified finish date

Tasks that must finish by a specific date

Start No

Later Than

(SNLT)

Starts the task on or before the date you enter Allows schedule changes to move the start date up to, but not later than, the specified start date

Tasks that must start by a specific date

Must Finish

On

(MFO)

Finishes the task on a specific date

Schedule changes don’t affect the finish date

Tasks that must finish on a specific date

Must Start On

(MSO)

Starts the task on a specific date

Schedule changes don’t affect the start date

Tasks that must start on a specific date

Constrain a Task to Start or Finish On or Near a Specific Date

If a task must start or finish on or near a specific date, just linking tasks and adding lead or lag time might not do the trick This may be the time to set a constraint The type of constraint you set for a task depends on the task’s scheduling requirements

To set a constraint

1 On the View Bar, click Gantt Chart

2 In the Task Name field, select the task you want, and then click Task Information

3 Click the Advanced tab

4 In the Type box, click a constraint type

As Soon As Possible is the most commonly used constraint

5 If you selected a constraint other than As Late As Possible or As Soon As Possible, click a constraint date in the Date box (Otherwise, Microsoft Project uses the task’s current start or finish date.)

Microsoft Project adds the constraint and recalculates the schedule

It’s also a good idea to check the necessity of your constraints occasionally

To check a constraint

1 On the View Bar, click Gantt Chart

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

3 In the Tables list, click Constraint Dates

4 Click Apply

Microsoft Project replaces the fields in the Gantt Chart view, listing the task constraints If necessary, scroll to see the fields

Warning: Dragging in Constraints

If you create a task by dragging on the Gantt Chart or Calendar, Microsoft Project imposes a constraint date on the task A constraint is also applied if you drag a task bar to move a task on the Gantt Chart or Calendar Microsoft Project assumes that because you’re dragging a certain date, you’re indicating a start or finish date for the task The constraint imposed is Start No Earlier Than or Finish No Earlier Than, depending on where you start and finish dragging Microsoft Project imposes the same constraint types when you type a start or finish date for

a task

Resolve a Task Constraint Conflict

A task with an inflexible constraint can cause a number of problems Predecessor tasks might not finish before a constrained task starts Resources might become overloaded with work You can be informed of these conflicts

by using the Microsoft Project PlanningWizard

If the PlanningWizard is turned on, it displays a message each time you set a constraint that causes or might cause a scheduling conflict The message describes the conflict and provides a list of several options, from canceling the constraint to setting the constraint and continuing on Choose the option that’s appropriate to your situation

The PlanningWizard can help prevent you from getting entangled in messy scheduling conflicts If you have inflexible constraints in your schedule, be sure you turn on the PlanningWizard

If the PlanningWizard is not on, you will not see the PlanningWizard but you may see an alert message

To turn on the PlanningWizard

1 On the Tools menu, click Options

2 Click the General tab

3 Under PlanningWizard, select the Advice about errors check box