We recently covered dependencies (not explicitly though) while covering the concepts of Lead and Lag.
3 Main Types of Dependencies
1. Finish to Start (FS) Dependency
The first (predecessor) activity needs to finish before the second activity can start. Baking a cake has to be 100% complete before decoration of cake can begin
2. Start to Start (SS) Dependency
An activity can start as soon as its predecessor starts. Baking a cake and starting to make icing are two activities that can start together
3. Finish to Finish (FF) Dependency
An activity cannot finish until its predecessor finishes. Delivery of the cake can only be done once the decoration of cake is complete
In some texts you will also find Start to Finish (SF) Dependency. From PMP perspective, the three main dependencies mentioned above should do the trick so don’t worry about it.
More Dependencies!
Dependencies also have 4 forms. They are listed below with examples,
1. External Dependencies
The project may have dependencies that are outside the scope of the project itself! For example, you may have arranged an evening high-tea treat for your colleagues at the pantry. But right before that there was a team lunch and for you to start your arrangements the previous team lunch members must leave
2. Internal Dependencies
As opposed to the above, the project may also have dependencies that are totally within the project scope and can be managed. For example, coding must finish on time for testing to stay on track. Classic example but works like a charm!
3. Mandatory Dependencies (aka Hard Logic)
Refer to the Finish to Start (FS) Dependency above. Decorate Cake can only begin once the Bake Cake activity is complete. Dependencies like these are simply mandatory because of the very nature of work. These must be addressed
4. Discretionary Dependencies (aka Soft Logic, Preferential or Preferred Logic)
These dependencies are simply the preference of the team. For instance, no team meetings on Fridays!
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