The term activity sequencing refers within the context of project management to a dual process. Initially, activity sequencing involves a specific process of the identification of dependencies among a series of schedule activities. The next step of activity sequencing involves the documentation of the said series of dependencies among those schedule activities. More specifically, activity sequencing involves the chronicling the dependencies among these schedule activities and putting them into a logical order. Activity sequencing also involves a careful examination of the relationships between schedule activities and their precedence relationships, which is also provides a tangible benefit to the development of an accurate schedule. Some techniques of activity sequencing that are particularly effective include precedence diagramming method, arrow diagramming method, schedule network templates, dependency determination, and the application of leads and lags. Some outputs from activity sequencing include project network schedule diagrams, activity list updates, activity attributes updates, and requested changes. This term is defined in the 3rd edition of the PMBOK but not in the 4th.
Welcome to the second lecture video in the Time Management Module. In this lecture video, we will discuss the Project Time Management Processes, Define and Sequence Activities, including the Precedence Diagramming Method.
At the end of the lecture video, you will be able to: Define an activity, Describe the transition from scope to schedule, Explain the Precedence Diagramming Method, or P-D-M, Distinguish the difference between a mandatory and discretionary dependency, and Define lags and leads. As a reminder, in the Scope Management Module, we defined a Work Package as the lowest level in a Work Breakdown Structure. An activity represents the effort needed to complete a work package. You can also refer to activities as tasks. The Project Time Management process, Define Activities, is the process of identifying and documenting the specific actions to be performed to produce the project deliverables.
It is at this point, that we can transition from the project scope, the high-level breakdown of work to be performed, to defining and planning the smaller, more manageable, schedule activities. Once we have defined the project activities, we can then sequence them. Sequence Activities is the process of identifying and documenting relationships among the project activities. A benefit of this process is that it identifies a logical sequence of work, which in turn will help the project team work more efficiently. Let’s look at an example of defining and sequencing activities. In this example, I am baking a pizza. First, I’ll list all the activities that need to be done in order to create the deliverable, the finished pizza.
Activity A, Make dough, B, Wash Toppings, C, Cut toppings, D, Preheat oven, E, Add toppings, and F, Bake. Notice that I’ve listed each activity on a separate note. That way I can move them around and sequence them in a logical order. Now, to put them in order, I can start at the beginning or the end. In this case I know that baking comes last, so I will put Activity F, Bake, at the end, over to the right. Next, I know that making dough is a starting process, so I will put Activity A, Make Dough, at the beginning, over to the left. I’ll then begin to order the rest.
So I know I need to wash toppings before I cut the toppings, but I don’t have to make the dough before washing the toppings, there is no logical reason for that conclusion. Assuming that I have resources to do both activities at the same time, I could wash toppings at the same time as making the dough. Next, cut toppings would follow wash toppings in our sequence. Then, in order to add toppings, I need to have the dough made and the toppings cut.
Finally, in order to bake the pizza, I need to preheat the oven, but again, there is no logical link between pre-heating the oven and the other activities, so I could start preheating the oven at the same time as making the dough and washing the toppings. To sequence the pizza making activities, I used the Precedence Diagramming Method, or P-D-M, a technique in which activities are linked, by one or more logical relationship, to show the sequence in which activities are to be performed. P-D-M uses four types of dependencies or logical relationships. We call these predecessor-successor relationships. The predecessor is the activity that comes first. In Finish-to-Start, or F-S, Activity A must finish before B can start.
In Start-to-Start, or S-S, Activity A must start before B can start. In Finish-to-Finish, or F-F, Activity A must finish before B can finish. And, in Start-to-Finish, or S-F, Activity A must start before B can finish. In this example, I used the word must. As in, Activity A must finish before B can start. This is a mandatory dependency. Mandatory dependencies are either legally or contractually required, or simply a necessary part of the work. In some cases, I may choose to sequence one item before another, not because it has to be in that order, but because I choose to do it in that order.
You would use this type of relationship, known as a discretionary dependency, when you have one resource doing several activities. Since one resource can’t do them all at once, you choose to put them in a sequence using Finish-to-Start. It is important to be able to distinguish the mandatory dependencies from the discretionary dependencies, because the discretionary ones can be changed. You usually can’t change mandatory dependencies. Once the relationships and dependencies have been established, the project management team must also determine which dependencies will require a lag or lead. Lags and leads are ways to put time between two activities in order to accurately define the logical relationship.
Lags are the amount of time a successor activity will be delayed with respect to a predecessor activity, resulting in added or positive time. For example, If Activity A is painting a wall and Activity B is hanging pictures, I might put a four day lag between these two to allow the paint to dry. The added time does not consume resources nor require effort, so we just add the time to the relationship between these two activities. This relationship would be referred to as Finish-to-Start with a four day lag. Leads are the amount of time a successor activity can be advanced with respect to a predecessor activity, resulting in subtracted or negative time. Simply put, leads are negative lags.
For example, if I need to paint after Activity A, I may have an activity to order paint supplies four days before Activity A ends to cover the lead time I need to get the supplies. So, Activity B would start four days before Activity A ends. This relationship would be referred to as Finish-to-Start with a four day lead. Now that we’ve discussed the four types of P-D-M relationships, as well as mandatory and discretionary dependencies, let’s add these to our pizza making project. I will draw lines between the activities to represent my sequencing and create relationships between the activities.
In the first sequence, make dough must finish before I can add toppings, so I have created a finish-to-start relationship with a mandatory dependency between these two activities. What types of relationships and dependencies are represented in the following sequences? In the second sequence, I must finish washing toppings before I can start cutting toppings, and after I finish cutting toppings, they will be ready to add. The activity, preheat oven, must finish before I can start baking, and I must also finish adding toppings before I can bake the pizza. All of the sequences I just described are Finish-to-Start relationships with mandatory dependencies.
This graph of the logical relationships we’ve established for our pizza baking activities is referred to as a Project Schedule Network Diagram. You can produce this diagram by hand or with the help of project management software. Next, I will add the duration of each activity. I will place this information on the top center of each note using the method activity-on-node, or A-O-N, which is simply one way of representing a precedence diagram. We will discuss estimating techniques in the Cost Management Module, but for now, assume I have estimated the durations for each activity. The activity, Make Dough, has an estimated duration of 12 minutes. I’ve estimated durations of two minutes to wash toppings and
The activity, preheat oven has an estimated duration of eight minutes. And I’ve estimated durations of four minutes to add toppings and ten minutes to bake. This brings us to the end of this lecture video on Define and Sequence Activities. The next step in this sequence would be to review this section in your workbook and complete the Knowledge Check, while the information is still fresh in your mind. In the Project Schedule Management knowledge area, one of the steps in the planning process involves sequencing project activities. This means arranging them in order and deciding what should happen, when it should happen, and considering it all in relation to the other scheduled activities. The order in which activities happen is called the activity sequence. Section 6.3.2.2 of the PMBOK Guide, 6th Edition clarifies some of the ways in which activity sequencing comes to be. Sequencing attributes are explained according to two separate dimensions; Mandatory vs. Discretionary and Internal vs. External. Based on which characteristics are attributed to the sequence, the sequence can be classified as one of four different types. This concept is often overlooked by new project managers, but it shouldn't be. Knowing and understanding the different types of sequence dependencies provides a lot of benefits. Foremost, it helps a Project Manager scheduling a project to better understand the schedule, which in turn leads to improvements in the overall quality of the schedule and its creation process. Further down the line, understanding these kinds of dependency attributes allows a Project Manager to identify opportunities to compress the schedule, when doing so becomes necessary as it often does for a multitude of different reasons. Mandatory Dependency – This is a dependency ordering that has to take place and can be thought of as a, "must." Mandatory dependencies are also known as hard-logic and are fixed limitations, often determined by physics, legal requirements, or other non-flexible elements. Discretionary Dependency – Discretionary dependency orders aren't physically, legally, or otherwise fixed, but still considered to be a good idea to keep. "Should," is the best word to keep in mind when thinking about this type of dependency. They are considered discretionary because they are at the discretion of the project team who decides to implement them. Internal Dependency – Internal dependencies are dependencies resulting from forces internal to the organization conducting the project. They can be mandatory or discretionary and include processes, procedures, practices, or rules imposed by or created from within the organization. External Dependencies – These sequence dependencies are determined as such by forces outside of the organization undertaking the project. Laws, safety standards, principles of physics, and other dependency creators outside of the organization's control are examples of external dependencies. As with internal dependencies, external dependencies can be mandatory or discretionary. A great way to understand the concept is to apply it to a familiar topic. The process of getting and eating a pizza can be considered, by definition, a project. As such, the steps and activities involved in the process should all be familiar to us. We can use the sequence of activities among some of these steps to illustrate examples the four sequence dimensions.
About the Author: Mark Romanelli is a full-time lecturer in the Sports, Culture, and Events Management program at the University of Applied Science Kufstein Tirol (FH Kufstien Tirol) in Kufstein, Austria. His curriculum includes courses in Project Management and Strategic Project Development. He is a member of the Project Management Institute and a Certified Associate in Project Management.
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What is the name for the relationship which relates to the sequencing of project activities or tasks?
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