Dependency links
You can use four
types of task
dependencies (or
links) to define the
relationships between
tasks in your Project
plan.
If you link tasks, Project will automatically adjust your
schedule when any part of your plan changes.
If instead you enter specific start and finish dates for
tasks, you override that automatic adjustment. So you
see the advantage to understanding how Project
dependency types are used to link tasks.
Linking Project tasks
Linking tasks 101
After you define your
plan’s tasks and
estimate how long it
will take to complete
them, you’re ready to
schedule the tasks by
creating task
dependency links.
By default, Project schedules all tasks to begin on the
project’s start date and calculates the project’s finish
date based on the last task to finish.
When you enter task dependencies, Project adjusts the
schedule to assign more accurate dates to each task.
Linking Project tasks
Linking tasks 101
The picture illustrates
the concepts.
1
All tasks in a Project plan start at the project start date
unless you specify otherwise.
2
With no task dependencies or constraints applied, the
project finish date is the same as the longest task’s finish
date.
Linking Project tasks
Linking tasks 101
The picture illustrates
the concepts.
3
Task dependencies, such as the Finish-to-Start
dependency between the first and second tasks (shown
here), can change the project’s scheduled finish date.
Linking Project tasks
Predecessor tasks and successor tasks
The four dependency
types shown in the
picture can help you
schedule your realworld situation.
A predecessor is a task whose start or finish date
determines the start or finish date of its successor task.
A successor is a task whose start or finish date is
driven by its predecessor task.
Linking Project tasks
Predecessor tasks and successor tasks
The four dependency
types shown in the
picture can help you
schedule your realworld situation.
The type of relationship between a predecessor task and
a successor task determines the type of task
dependency to use.
Linking Project tasks
Finish-to-Start dependencies
When the work of
Task 2 can start only
after all the work of
Task 1 is finished, the
tasks have a Finishto-Start (FS)
dependency.
The FS dependency is created by default when you link
two tasks in Project. The order in which you select the
tasks treats the first as the predecessor, the second as
the successor.
Task 1 is the predecessor of Task 2, and Task 2 is the
successor of Task 1.
Linking Project tasks
Start-to-Start dependencies
When the work of
Task 2 cannot start
until Task 1 starts, the
tasks have a Start-toStart (SS)
dependency.
In the real world, SS dependencies generally occur
because you want the work of two tasks to overlap.
For example, “Level concrete” (Task 2) can’t begin until
“Pour foundation” (Task 1) begins.
Linking Project tasks
Start-to-Start dependencies
Overlapping work also
helps to reduce the
overall duration of a
project.
If Task 1 will take 10 days to complete, and Task 2 will
take 5 days to complete, and you set an FS
dependency, the overall duration of the two tasks is 15
days.
If you set an SS dependency, the overall duration of the
two tasks is only 10 days (the time required by Task 1).
Linking Project tasks
Finish-to-Finish dependencies
When the finish date
of Task 1 determines
the finish date of Task
2, they have a Finishto-Finish (FF)
dependency.
For example, “Inspect electrical” (Task 2) can’t finish
until “Add wiring” (Task 1) finishes.
Linking Project tasks
Finish-to-Finish dependencies
Like SS
dependencies, FF
dependencies reduce
the overall amount of
time it takes to
complete work on two
tasks, if the work can
overlap or be done in
parallel.
If Task 1 will take 10 days to complete, and Task 2 will
take 5 days to complete, and you set an FS
dependency, the overall duration of the two tasks is 15
days.
If you set an FF dependency, the overall duration of the
two tasks is only 10 days (the time required by Task 1).
Linking Project tasks
Start-to-Finish dependencies
When the start date of
Task 1 determines the
finish date of Task 2,
the tasks have a
Start-to-Finish (SF)
dependency. This is
how you create just-intime scheduling.
Say a related task needs to finish before a milestone or
project finish date, but it doesn’t matter when and you
don’t want a late finish to affect the just-in-time task.
Create an SF dependency between the task you want
scheduled just in time (the predecessor) and its related
task (the successor).
Linking Project tasks