Introduction to Project Schedule Management

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Time is valuable, and everyone’s life runs on a clock. Whether at home or work, we always ask ourselves, “How long will this take me? Is there any way to finish sooner?” In the project sense, how long activities take becomes an important matter of cost. That’s why schedule management is so important.

In this first article of our three-part series, we will explain what schedule management is and what a typical project schedule looks like. We hope this helps you get started in scheduling your own projects successfully.

What is Scheduling in Project Management?

Schedule Management is the process of defining project tasks and their durations, dependencies, and assigned resources in order to complete the project within a designated time frame. It also includes monitoring and reporting on the schedule to ensure the project is delivered on time.

Time is one of the three constraints in the “Iron Triangle” of Project Management, and any delay in the schedule can be very costly. Therefore, Schedule Management is crucial to ensure project success.

Schedule Management allows for (among other things):

  • Structuring project work,
  • Sharing the plan with the whole team,
  • Gathering data for reporting,
  • Defining the interdependencies between tasks /activities and the task force,
  • Visualizing the critical tasks which are important to pay special attention to,
  • Understanding the project status in relation to the validated road map,
  • Increasing the likelihood of achieving the project objectives.

The project schedule is a detailed plan defining how and when the project will deliver its products and services as defined by the project scope.

The schedule is closely tied to the definition of work to complete; therefore, its structure is aligned to the organization of this work, that is to say, the WBS (Work Breakdown Structure).  This is a detailed plan of the tasks or activities to be carried out over the time frame of the project. This also allows for estimating the resources needed on the project and thus consolidating a budget.

The schedule consists of all the tasks, or activities, necessary to complete the project deliverables. These tasks are connected by links called dependencies. The resulting “network” of tasks then becomes the basis of scheduling analysis.

The schedule allows project managers:

  • To ensure the project  objectives are met on time,
  • To identify how much time is flexible for these objectives to be met (float), and
  • the project float (called total float), which is the gap between the sequencing of the most important project tasks with the longest duration (the critical path) and the objective,
  • To consolidate the forecast of expense over time (the budget), which will support project cost control.

Throughout the project, the schedule allows task progress to be measured against the baseline and future tasks to be re-forecasted accordingly. This way, it serves as a measure of project performance. The baseline may evolve, but only under strict conditions as it’s integrated with the approved scope and budget.

A Project Schedule can be represented in a Task Network Diagram, which maps the sequence of tasks and their dependencies. The following image depicts a typical Task Network Diagram:

Task Network Diagram to plan and visualize project tasks

More commonly, a schedule is represented in a Gantt Chart, which lists each task chronologically with each of their durations and dependencies.

Example of a Gantt chart to manage a project schedule

Project Tasks

Tasks (or activities) correspond to a part of the work that needs to be done. They have a beginning, an end, and a duration. Several aspects of a task must be identified: the expected result, who is responsible for it, the resources needed, and any input data necessary for its implementation.

Project Milestones

Milestones are significant events or deliverables of the project. They have a duration of zero.

Task Relationships

Task Relationships (sometimes called dependencies) are the links between tasks that connect them. They identify a task’s predecessors (the tasks that come first) and its successors (the tasks that follow). There are several relationship types:

  • Finish-Start (FS) – Task A must finish before Task B can start. (This is the most common type)
  • Start-Finish (SF) – Task A must start before Task B can finish.
  • Start-Start (SS) – Task A must start before Task B can start.
  • Finish-Finish (FF) – Task A must finish before Task B can finish.

Lag & Lead

Lag or Lead can be applied to each task relationship. These are offsets that can be positive (adding time) or negative (saving time). For best Schedule Management practice, it is best to limit these as much as possible and to explain each task as well as possible.

Lag vs Lead of tasks in a project schedule
  • Lag is a delay from the finish of Task A to the start of Task B. For example, let’s say I can only start Task B 5 days after Task A finishes. This positive shift (or lag) may represent the transportation of an item that is not controlled by the project.
  • Lead, on the other hand, is when Task B has been moved ahead of its start date. For example, I may want to start Task B in anticipation of the end of Task A.

It is best to break down the predecessor task (Task A) to clarify exactly what deliverable is expected to start the successor task (Task B) on a certain date.

Project Task Constraints

Constraints are limitations or restrictions imposed on the project schedule for the execution of a task. They usually take the form of imposed dates, for example, “as late as possible”.

Project Float

  • Free Float is the amount of delay that can be added to a task without its successors being delayed,
  • Total Float is the total amount of delay that can be added to the end date of a task without delaying the end date of the project.

Consider the following example:

Total float vs free float in a project schedule
  • Task A has no free float and a total float of 5 days,
  • Task B has a free float of 5 days and a total float of 5 days,
  • Task C has a free float of 5 days and a total float of 10 days.

Several important dates frame the schedule and provide important information on the project’s status:

  • Status Dates are the set of dates (planned or realized in the past) that represent an update of the schedule. They indicate when the project is current and provide the most accurate projection of the project’s completion.
  • Baseline Dates are the set of dates that define when each task should be carried out. They are determined by the project stakeholders and based on the availability of resources to achieve the project objective. The Status Date is generally compared to the Baseline Date to measure project performance and the ability to meet its objectives on time.
  • Actual Finish Dates are the dates on which each task or activity is actually completed.

Now that we’ve reviewed the elements of a schedule, let’s look at how to apply them together. In our next article, we will review how to build a project schedule.

This article series was written by Sébastien DESLANDES, Jeremy LESCOP, and Christine ORIARD with contributions from the MIGSO-PCUBED Scheduling Community of Practice.

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