Precedence Diagramming Method – What Is It and How to Create It?

precedence diagram in project management

Many people and resources unite and invest their energy to create a successful project. Often the project journeys from one team to another, demanding various things from different individuals. Every step ahead takes you closer to your end goal.

The journey, however, is not always a straight one. Some tasks may need a catalyst, and others may require different resources to keep the process going. Sometimes projects move from one end and shift to another midway.

Be it this or that; it is essential to understand the whole process and employ valuable tools and techniques to streamline it. Precedence Diagramming Method is one such way of making project management more accessible and more efficient.

This article will introduce you to Precedence Diagramming Method and then explain the specifics. Hop on and enjoy the ride.

What is Precedence Diagramming Method?

Precedence Diagramming Method (PDM) is used in Project Management to create visual project schedules indicating tasks and dependencies. 

It is essentially a scheduling technique that allows you to visualize the sequence of different activities within a project as well as the dependencies between these activities.

PDM is a useful visual tool for PMs since it allows them to quickly identify task dependencies. Nodes and arrows are used to construct the diagram wherein nodes represent different tasks and/or activities while the arrows drawn between them indicate the relationship between these tasks. The diagram is also called a nodal diagram or a network diagram.

Before we move on to the creation process, let’s look at the dependency relationships between different tasks.

Types Of Task Dependency Relationships In PDM

Four types of task dependency relationships can be seen in PDM depending on the sequence of different tasks. These are:

1. Finish-to-Start (FS) Dependency:

In the case of Finish-to-Start dependency, the predecessor must be completed to initiate the next task. In simple words, the completion of Task A is necessary for the initiation of Task B. The initiation of Task B is dependent on the completion of Task A. 

In this relationship, the arrow is directed straight toward Task B.

2. Finish-to-Finish (FF) Dependency:

Finish-to-Finish Dependencies require the completion of both the predecessor and the successor. The completion of Task A depends on Task B’s completion and vice versa. Both the tasks, as such, are completed on the same date or at the same time.

3. Start-to-Start (SS) Dependency:

In Start-to-Start dependencies, tasks are connected simultaneously at the start, i.e., the successor and predecessor start. Task B cannot start until the initiation of Task A and vice versa. Both tasks start at the same time in this type of relationship.

4. Start-to-Finish (SF) Dependency:

Lastly, in Start-to-Finish dependencies, one task’s completion depends on the initiation of another. In this case, the initiation of the predecessor is linked to the completion of the successor. Task B cannot be completed until Task A starts, and vice versa.

In simpler words, remember the first part of each of these relationships has to be obtained to achieve the latter’s status.

Let us now take a look at the types of dependencies that exist in PDM.

precedence diagramming method

Types Of Dependencies In PDM

Four types of dependencies can exist between different tasks in a project. These are:

1. Mandatory Dependency:

Mandatory dependency, also known as complex logic, is a compulsory relationship. There exists a mandatory relationship between different tasks. One cannot proceed to the next activity without satisfying the prior condition.

2. Discretionary Dependency:

Discretionary dependency, also known as soft or preferential logic, focuses on optimizing resources for better results. As such, the team can make changes and adjustments to the sequence of activities to reap more profitable results.

3. External Dependency:

External dependency is not under the control of the project owners or team members. It can include government approvals, investment or funding, etc. The conditions are totally dependent on matters outside the control of the team.

4. Internal Dependency:

An internal dependency exists within different project activities. In this type of dependency, the next project cannot be started until the completion of the previous project.

Although there is no mandatory dependency, the initiation of the next project depends on the completion of the previous one. This type of dependency is under the organization’s control, which is why it is termed internal dependency.

Moving on to the crux of our pose, how can you create a precedence diagram for your project?

How To Draw a Dependency Diagram?

This section will explain how you can create a dependency diagram for your project. The process is simple and to the point. Just follow the following steps, and you will be able to draw your own diagram relatively easily:

1. Create Work Breakdown Structure:

Projects as full-fledged chunks can be daunting. To make the whole process easier and more efficient, start by creating a work breakdown structure (WBS).

The Project Management Institute (PMI) Project Management Book of Knowledge (PMBOK) uses the term “deliverable-oriented hierarchical decomposition” of a project to define the work breakdown structure. It breaks down the larger project chunks into tiny, easily deliverable pieces.

The development of the WBS allows you to identify the minute details of tasks, such as the time duration, resources required, etc.

2. Create A Task List:

Once you have identified all the tasks to be included in the project, you can start creating a list. In this list, organize all the tasks and identify the sequence of these tasks in the project.

3. Add Dependency Relationships:

 Now that you have a task list, you can start determining the dependency relationships between different tasks.

This method step forms the backbone of the whole process, so ensure you accurately identify task dependencies. Your project’s successful and timely completion depends on this project schedule.

4. Start Drawing:

By the end of the last step, you will have all the information you need in your hand. Now is the time to start drawing the diagram itself. Create different nodes using a box diagram indicating the tasks involved in the project. Each box diagram or node is connected to other tasks via arrowheads that represent the type of relationships that exists between these tasks.

The direction of the arrow will allow the team to determine the relationship between the tasks, so make sure this part of the process is also done meticulously.

Now that you have gained ample understanding of the method and how to create a diagram, it is time to take a look at some of the benefits you can get by employing the method for project management.

Benefits Of Precedence Diagramming Method

Here are a few pointers that can indicate the plenty of benefits you can reap by employing the method in your business:

· Accurate Project Scheduling:

One of PDM’s biggest and most powerful advantages is that it helps PMs create accurate project schedules. PMs can clearly identify and define all the tasks involved in the process. Not only that, but they can also accurately determine the sequence of these tasks in the project.

· Visual Representation:

Visual representation of the project schedule is especially appealing for the PMs as well as the members of the team. With the diagram in sight, they can quickly identify the tasks and their sequence and streamline the process for better results.

· Highlights Task Dependencies:

We cannot talk about Precedence Diagramming Method without mentioning how it accurately highlights dependencies between tasks. Task dependencies make it much easier to follow the schedule and ensure the timely delivery of the end products.

· Determine Critical Path:

Since Precedence Diagrams show the tasks and dependencies, PMs can quickly determine the critical path for successful project completion.

· Helps Avoid Risks:

Another great benefit of the method is that with the development of the diagram, you have a clear view of the project schedule and easily determine potential risks that may crop up during the project. You can then prepare for countermeasures to resolve these risks before they threaten your project’s successful completion.

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Using PDM To Create Precedence Diagram in nTask

Until now, we focused on PDM and how to create a diagram. The next step in the journey is creating a diagram using nTask.

While creating a Precedence diagram may seem scary, with the right tool in hand, you can easily create the diagram and attain plenty of other benefits that will make your project management journey significantly more manageable.

You can easily create a Precedence diagram of your project using nTask’s Gantt chart module. The process is much more straightforward than you’d think. All you have to do is create a list of all the tasks in the project via nTask’s Gantt chart.

Multicolored bars will appear in front of each task, indicating each task’s status.

All you have to do now is create a relationship between the tasks by clicking on the grey circle next to each task and stretching a line to your desired point. The box above will indicate the type of relationship established. Repeat the method for all the tasks, and voila! Lo and behold, your Precedence diagram is ready.

If you are searching for a tool to create your Precedence diagram, look no further because nTask can do that for you. Start now with a free trial of 7 days, or book a demo with our sales team for further assistance.

Good Luck!


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