If a task is relatively large and requires several users with different skills to manage, break the task into subtasks and create parent-child relationships. A child task should be a relatively smaller, manageable size of work. When you group child tasks together under a parent, values such as dates, costs etc. aggregate and roll up to the parent task. So the parent task takes on the form of a summary task or rollup task for its child tasks. Planned start date and Planned end date rollup occurs when you create child tasks: the duration of the parent automatically adjusts to cover its child tasks.
A parent-child relationship is different from a dependency relationship. In a dependency, one task must finish before another begins. In a parent-child relationship, any number of tasks can be nested under a parent task with or without any dependencies.
Creating a Parent-Child Task Relationship
To set parent-child relationships, select a task that you want to convert to a child task and click on the Make Child button.
Shortcut – Alt + Right arrow key
To create a parent task from a child task click on the Make Parent button.
Shortcut – Alt + Left arrow key
Parent-Child (Rollup) Task Calculations
Rollups involve date changes, state changes, and value calculations.
Estimated Start Date: set to read only for parent tasks.
Estimated End Date: becomes read only.
Baseline Start Date: becomes read only.
Baseline End Date: becomes read only.
Actual Start Date: becomes read only.
Actual End Date: becomes read only.
Percent Complete: becomes read only.
Estimated Cost: becomes read only.
Baseline Cost: becomes read only.
Actual Cost: becomes read only.