Two activities are called ‘dependent’ if one’s timing is dependent on that of the other, such as when one finishes the other one starts, or when one is to start exactly in a week after the other is complete.
In activity dependency, the following definitions are used:
- Master activity - the one whose start or end date is used as a reference for another activity.
- Dependent activity - the activity that starts/ends according to a rule, called dependency, linking it with a master activity's start or end date.
To set a dependency between two activities, follow this procedure:
- Log in as user with ‘Add new activities’ permission (e.g. Project Manager). If you are already logged in, skip this step.
- Open Activity Center.
- Locate the activity whose dependency you want to change.
- Click the dependency attribute button ().
- Select among three types of dependency available: Start to finish, Finish to start, and Start to start. Selecting any of the three options other than No dependency opens additional fields, such as in the illustration below.
- Start to finish dependency means the dependent activity will finish the same day the master activity starts.
- Finish to start dependency means the dependent activity will start on the day following the master activity's end date. And,
- Start to start one means the dependent activity will start the same day the master activity starts.
- Use the slider, or type in the required lag in days. This will set the dependent activity to start/finish # days after/before the first one finishes, depending on whether the delay is a positive or negative integer (e.g. -3).
Below are examples of how each type of dependency would be used, in a real world example. We've chosen making and selling home-made jam from freshly picked berries to illustrate each type:
- Finish to Start (F-to-S): You need to "Finish the task of picking the berries" before you can "Start the task of crushing and mixing the berry mixture" for cooking.
- Start to Start (S-to-S): You need to cook the berries, and then put them into sterilized jam jars. You can "Start the task of cooking the berries" and "Start the task of sterilizing the jars" at the same time.
- Start to Finish (S-to-F):Your Jam is very popular and you have many orders from interested shop owners. This kind of dependency is best used when you know when your customers need to have the jam delivered and in their stores (for Christmas or Thanksgiving, for example). So, you know the end date of the last task, and your predecessor tasks will have their start dates created by working backwards from there. Further, durations become more important than actual start dates or end dates for preceding tasks, in this type of dependency.
You can have two or more dependencies (up to 10) created for an activity. Only activities that can be linked with it by dependency will appear on the Depends on drop down list.
- To create another dependency for the activity, click 'Add more dependencies'. A new tab will appear.
- Follow steps 3 to 5 above to create new dependency.
- If more dependencies are needed, use the green '+' button.
- user must have ability to view all, or at least be able to view the activity they want to make the master,
- the master activity must be within the same project as the dependent one,
- master activity must have a start or end date, to correspond with the type of dependency, i.e. 'starts when finished' needs the master activity to have an end date,
- the relationship must not create a circular reference, i.e. A depends on B which depends on C which depends on A, this includes Parent tasks.
- Parent Tasks - related to dates and circular references is the fact that you can't make a parent task a master task because parent task start/end dates reflect the dates of its child / sub tasks, so adding a parent as a master task would create a circular reference - double check the master task you want to set is not a parent task to child tasks dependent tasks.
To delete a dependency:
- Enter the dependency editor as described above for the activity you want to edit.
- For multiple dependencies: Select the dependency you want to delete by clicking the respective tab.
- Click 'Remove dependency'.
For instructions how to delete a dependency when in Gantt view, see here.