Gantt Chart: 4 Types of Task Dependencies in Project Management

Gantt Chart and Dependencies

A  Gantt Chart is a scheduling tool used in project management to show what has to be done and when. It visualizes task relations and converts it into a diagram, and makes it easy to read the schedule of tasks. However, you have to know the task dependencies to understand the chart. 

Task dependencies are used to specify the relationships between two tasks and to indicate when one is supporsed to begin or end in relation to the other one. On a Gantt Chart, task dependencies are composed of lines linking two tasks as shown below.

According to PMBOK Guide, A Guide to the Project Management Body of Knowledge, a dependency refers to a logical relationship between two activities and all tasks should have a dependency. This is because by definition, if a task is part of a project it must be related to other tasks. The four typical dependencies are:

1. FS: finish to start
2. FF: finish to finish
3. SS: start to start
4. SF: start to finish

Finish to Start

A FS dependency means Task A must be finished before Task B can be started. It is the natural dependency that each predecessor task would finish prior to the start of its successor task.

Sometimes, tasks are overlapsped necessarily, which falls to the FF, the SS, and the SF relationships as shown below. 

Finish to Finish

A FF dependency means the dependent Task B cannot be completed until Task A is completed. 

Start to Start

A SS dependency means the dependent Task B cannot begin until Task A begins. 

Start to Finish

A SF dependency means Task B cannot be completed until Task A begins.

"Nothing is particularly hard if you divide it into small jobs."

                                                                                                                 - Henry Ford

Task Relations in ZenTao

The four task dependencies are supported in ZenTao-Gantt Chart features. Except task dependencies, parent-child tasks are also supported in ZenTao. If a task is chunky and requires several users to do, it usually would be divided into child tasks. A child task is relatively small and manageable size of work. In ZenTao, you can create a task and then add child tasks for it. Click HERE to read more.

Reference

1.  https://support.microsoft.com/en-us/office/link-tasks-in-a-project-31b918ce-4b71-475c-9d6b-0ee501b4be57?ui=en-us&rs=en-us&ad=us

2.  https://www.zentao.pm/book/zentaopromanual/free-open-source-project-management-software-ganttchart-138.html

3.  https://en.wikipedia.org/wiki/Dependency_(project_management)