What is the difference between a schedule network model and a schedule network schedule?

With this material I want to open a series of articles on the topic of schedule network planning, since this issue has been of keen interest to all project participants for many years.

The role and place of schedule network planning within the project life cycle have always caused different reactions from participants in the project management process and sometimes range from a complete understanding of the information return that can be obtained from competently performed actions to complete neglect of issues related to managing project deadlines. Until now, some project managers have the opinion that it is possible to manage the progress of a project using "graphs" developed in Excel. And even if the "graphs" are developed not in Excel, but using specialized software - Microsoft Project or Oracle Primavera, the situation when such a "graph" is already faded in the sun, because it has been hanging on the wall of the project management team room for almost a year, and according to which the project manager is trying to manage his project, unfortunately, also, albeit very rarely, still occurs.

So what is the role of scheduling and where does it fit into the project management process?

I remember the informal definition given by one of the speakers at the project management forum held in Moscow in 2023. He said that The schedule network model is the Heart of the project. The heart, which drives a fresh portion of informational oxygen through the project's vascular system and feeds the brain (the project management team led by the project manager) with fresh and relevant data to develop those management reactions that will allow the project to be completed successfully and achieve its goals. And it is necessary to devote time and make efforts to develop the correct tool for managing project deadlines. Namely, to develop the correct schedule network model.

You may already have a question - "the article mentions two terms - schedule network schedule and schedule network model. Is there a difference between these two concepts? Yes, there is and it is colossal! In many ways, the success of the project in achieving its goals, taking into account the existing limitations, depends on understanding this difference.

Let's look at these differences.

So, what is a network schedule? Let's look at the example shown in Figure 1.

Figure 1

What do we see? We see a "graph" that operates only with dates and durations. At the same time, if you plan the timing of the project, relying only on the specified parameters (timing and duration) and not paying attention to the issue of assigning resources to the project tasks, then you get a picture that is quite reassuring to the project management team - we have met the deadlines, we have all the tasks planned, which means we can continue to live in peace. And this is where the most common mistake lies. Let's try to look at the same example, but with resources assigned to tasks.

Figure 2

And once you and I have assigned the resources that are required to complete the assigned tasks, we begin to understand that the pretty picture has just ceased to exist. Because we have a total of 3 welders and 3 assemblers available. This means that I will not be able to perform jobs number 1 and 2 (limited resource - welder) and jobs 3 and 4 (limited resource - installer) in parallel. That is, we are faced with the problem of choice: either we quickly need to buy additional resources (2 welders and 4 installers), which will inevitably lead to an increase in project costs, or to equalize the resource load, which will inevitably lead to an increase in the project implementation time. Thus, the project manager and the project management team are visualized with a real picture of the timing of the project, taking into account the assigned resources, in this case labor. And this gives the project manager a tool for making management decisions to optimize deadlines.

So, let's summarize the above and try to define the schedule network schedule and the schedule network model.

A network schedule is a tool for planning the timing of a project, which operates only on the start (completion) dates of project tasks and the duration of execution of these tasks. Taking into account technological interdependencies between project tasks.

Schedule network model - let's try to present the definition in the form of a diagram in Figure 3:

Figure 3

Thus, it is the use of the schedule network model that allows the project manager and the project management team at the planning stage to obtain a realistic picture of the planned time frame and identify bottlenecks in advance.

However, the benefits of the schedule network model do not end and are not limited to the planning stage. We will talk about this in the following articles.