Activity Dependencies

Posted on June 17, 2009 by

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A project is composed of many smaller activities. Although some activities are independent of each other, others have dependencies that must be accounted for when making the project schedule. Using the Precedence Diagramming Method (PDM), there are four types of dependencies that two activities can have with each other. These four types of dependencies are: Finish-to-Start, Finish-to-Finish, Start-to-Start, and Start-to-Finish. The names of these dependencies describe what must happen to activity “A” before what can happen to activity “B”. For example, for a Finish-to-Start dependency, activity “a” must finish before activity “b” can start. Here is an example of a Finish-to-Start dependency: Katy must finish mixing her cookie batter before she can start shaping the dough into cookies. Mixing the cookie batter must be completely done before individual cookies are made. Here is an example of a Start-to-Start dependency: Katy must start shaping the dough into cookies before she can start baking them. She doesn’t have to finish the whole activity of shaping all the dough into cookies, but she has to at least start this activity so that she has some cookies that can start baking while she shapes more.