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 is a
relatively smaller, manageable size of work.
When you group child tasks together under a parent, values such as Estimated
cost 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. When you create a parent-child
relationship, the parent task number is saved in the Parent field in the
Project Tasks table. All project management tasks have a parent: either another project task or
the project itself.
Unlike a dependency, a parent-child relationship is not saved as a record in any table. The
only modification that takes place when a parent-child relationship is modified is the
Parent field in the child task record.
You can create predecessor-successor relationships between child tasks with different parents,
between two different parent tasks, or between a child task and another parent task. However, if
the predecessor task finishes after the successor task starts, creating a dependency between
child tasks that have different parents is not allowed.
Note: On the Gantt chart, you can drag-and-drop the parent task to move the entire hierarchy to a
new location on the schedule.