A dependency is a directional relationship between two planning elements in a network diagram that reflects a logical and temporal relationship between these elements. The dependency between predecessor and successor activity is represented in the network diagram by arrows. Interdependent tasks or activities that must be finished before the project can be finished are displayed on the critical path.
There can be technical or content-related dependencies between the individual planning elements. This allows you to see whether a planning element becomes the predecessor or successor of another planning element or whether several tasks overlap. The type of activity link determines how the individual planning elements are dependent on each other. A distinction is made between the following types of dependencies:
The predecessor task or activity must finish before the successor task or activity can start.
E.g.: You have to finalize the purchase of the land, before you can start building a house on it.
The predecessor must start before its successor can start. Predecessor and successor don’t have to simultaneously, the successor can start any time after the predecessor has started.
E.g.: The moment you start cooking rice, you can start preparing the vegetables.
End-to-End: The predecessor must finish before the successor can finish. The tasks don’t have to finish at the same time, the successor can finish any time after the predecessor has been completed.
E.g.: If you didn’t build your house from scratch but ordered a prefabricated house, some tasks can only be finished after the “delivery” of the house is completed (e.g. adding the patio).
Start-to-End: The successor task can’t finish before the predecessor has started.
E.g.: You can only finish the billing process (successor) after you have started the delivery of your product or service (predecessor).