Posted by Larry Short
The three main kinds of predecessors are finish-to-start (FS), start-to-start (SS) and finish-to-finish (FF). There is a fourth type of relationship called start-to-finish (SF), but it is akin to my cousin Vinnie who we don’t talk about. For more information check out “the book,” page 138. It’ll tell you all you need to know.
The most common kind of predecessor is the finish-to-start. It’s called finish-to-start because the first activity finish leads into the second activity’s start. For example, when I entered the casino I had to first gamble before I could win money. (I like to think positive!)
The start-to-start (SS) predecessor is less common, but sometimes you need to coordinate activities so they begin at the same time. One example that occurs often in Vegas is to start gambling and drinking at the same time. The two activities don’t have to occur at the same time, but are often coordinated by the casino’s waitress to happen that way.
The finish-to-finish (FF) predecessor depicts activities that finish at the same time. An example might be that I lose all my money and my bank’s ATM stop working at the same time. Keep in mind that tasks like that are pretty rare, at least in project management, and almost never show up in network diagrams.