Dependency types

Four basic dependency relationships define the relationship between the start and finish of tasks: start-to-finish, finish-to-start, start-to-start, and finish-to-finish. You can set these dependency relationships on the Predecessors tab of the Task Information dialog box, as shown in Figure 4-22.

Figure 4-22: Four types of dependencies enable you to deal with every variable of how tasks can relate to each other's timing.

Tip Use the Lag column on the Predecessors tab of the Task Information dialog box to create lag time between tasks.

The first timing mentioned in each relationship name relates to the predecessor task and the second to the successor. Therefore, a start-to-finish dependency relates the start of the predecessor to the finish of the successor, and a finish-to-start relationship relates the finish of the predecessor to the start of the successor. Project refers to these relationships by their initials, such as SS for a start-to-start relationship.

Tip As you view the figures in the following sections, take note of the direction that the arrow points between tasks. The direction of the arrow provides important visual ^ clues about the type of dependency.

Finish-to-start (FS)

A finish-to-start relationship is the most common type of dependency and is, in fact, the only relationship that you can create by using your mouse or the Link Tasks tool or command. In the finish-to-start relationship, the successor task can't start until the predecessor task finishes. Examples of this relationship are as follows:

♦ You must write a report before you can edit it.

♦ You must have a computer before you can install your software.

In Figure 4-23, you see examples of the FS relationship in which the successor task can start as soon as its predecessor is finished. The following tasks have a finish-to-start relationship:

Finish-to-Start

Finish-to-Start

What Sucessor Project Management
Figure 4-23: In the FS relationship, successor tasks can't start until predecessor tasks finish.

Note The relationship between Tasks 4 and 5 also contains some lag time, as discussed *-'"' the section "Allowing for overlap and delays," earlier in this chapter.

Start-to-finish (SF)

With the start-to-finish relationship, the successor task cannot finish until the predecessor task starts. The following are some examples:

4 You can finish scheduling production crews only when you start receiving materials.

4 Employees can start using a new procedure only when they have finished training for it. If the use of the new procedure is delayed, you also want to delay the training so that it occurs as late as possible before the implementation.

Can you set up this start-to-finish example as a finish-to-start relationship? Not really. The idea is to allow no delay between training and implementation. If you set the new procedure to start only when the training finishes, the new procedure can start any time after the training ends, depending on how other relationships may delay it. If the training task has to finish just before the other task starts, delays of the later task (implementation) also delay the earlier task. This fine distinction will become clearer when you see projects in action.

Figure 4-24 shows a start-to-finish relationship between acquiring materials for Phase Two Testing and completing the analysis of Phase One Testing. Assuming that the test results of Phase One determine the materials that you'll need for Phase Two, you can't begin acquiring materials for Phase Two Testing until you have completed the analysis of Phase One Testing. Notice the direction of the arrow that connects the two tasks; it provides a visual clue of the type of dependency that exists between the tasks. In fact, the direction of the arrow in all dependencies provides you with valuable information.

Start-to-start (SS)

In a start-to-start relationship, the successor can't start until the predecessor starts. Consider the following examples:

4 When you start getting results in an election, you can begin to compile them. 4 When the drivers start their engines, the flagger can start the race.

In Figure 4-24, Tasks 9 and 10 have a start-to-start relationship.

Start-to-Finish

Figure 4-24: The successor task can't finish until the predecessor task starts.

Start-to-Finish

Figure 4-24: The successor task can't finish until the predecessor task starts.

Finish-to-finish (FF)

In the finish-to-finish dependency, the successor task can't finish until the predecessor task finishes. Consider the following examples:

♦ You finish installing computers at the same time that you finish moving employees into the building so that the employees can begin using the computers right away.

♦ Two divisions must finish retooling their production lines on the same day so that the CEO can inspect the lines at the same time.

Suppose that, in Phase Two of the testing in Figure 4-25, you can begin preparing the solution (Prepare solution 2) while you're still acquiring materials (Acquire materials 2). However, you can't finish preparing the solution until you finish acquiring the materials. Therefore, set up a finish-to-finish dependency between the two tasks to make sure that you don't finish preparing the solution if you experience a delay in acquiring materials.

Project Dependencies Finish Finish

Finish-to-Finish

Figure 4-25: The successor task can't finish before the predecessor task finishes.

Finish-to-Finish

Figure 4-25: The successor task can't finish before the predecessor task finishes.

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Project Management Made Easy

Project Management Made Easy

What you need to know about… Project Management Made Easy! Project management consists of more than just a large building project and can encompass small projects as well. No matter what the size of your project, you need to have some sort of project management. How you manage your project has everything to do with its outcome.

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  • gorbaduc
    Can an activity in ms project have a successor without a predecessor?
    2 years ago

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