Here is a very brief project overview introducing basic concepts of project planning, management and critical path analysis.
Definition of a Project
The Project Management Institute defines a project as follows:
A Project is a unique undertaking with a defined starting point and duration directed at achieving defined objectives, utilizing finite or infinite resources.
The key parts of this definition:
- A project has a unique objective.
- A project has a definite start, duration and finish. It has a temporary rather than open-ended duration.
Some obvious examples of projects are:
- Building a house
- Relocating an office
- Writing a book
- Developing a website
Project Management
Project management is the management of an organized set of activities directed toward a common goal, using specialized management structures and techniques. It includes:
Determining project objectives
What is the goal (or goals) of the project? Examples of project goals include building a bridge, relocating the MIS department to a new site or installing a new phone system. More importantly, some examples of things that are NOT projects include scheduling the usage for a training facility or scheduling engineers in a technical service department. These are not projects because they do not meet all the criteria of a project. They do not have a definitive start, finish, and duration.
Managing budgets and resources
Projects do not get done without resources to do them. To ensure successful completion of a project, it is important to estimate correctly the number of personnel and the amount of equipment needed. With this, it is important to realize the cost of the project. Some projects can be completed in a shorter time by increasing the manpower on the project. However, doing this also increases the cost. One of the project manager’s jobs is to maintain a balance between reducing costs and reducing the time to complete the project.
Reporting Progress
Reporting progress is a key to project management. It is essential that key players in a project know what is happening, and whether they are on track, behind, or ahead of schedule. By reviewing progress on a regular basis, you can try to avoid possible problems in advance. For example, if you notice that a certain task was scheduled to take 10 days to accomplish, but on day 5 only 25% of the work was finished, you could possibly re-allocate resources to that task in order to complete it on time.
Evaluating efficiency and effectiveness
During and after a project, it is important to review and analyze the performance on the project. This information can provide valuable insight into possible changes to make for future projects. For example, your project was to build a house, and one of the steps involved was landscaping. After the project is finished, you notice that it took less time to do the landscaping than you originally planned. This information could be valuable if you build another house, because you could reduce the time allocated for landscaping. By constantly reviewing the efficiency and effectiveness of your project, you can more accurately plan future projects.
Project Managers
Project managers are responsible for managing projects. They coordinate projects and related tasks, but do not usually have direct management responsibilities for resources assigned to their project. The resources involved in one project may not be the same resources involved in another project. Project managers focus only on work that is specific to their project, and are primarily task and time-constrained: “How do I ensure my project gets finished in the shortest amount of time?” is a question on every project manager’s mind each day.
Critical Path Method (CPM)
The definitions and calculations in this section assume a simple classical project consisting of a set of tasks, task dependencies, and task constraints.
A task dependency (relationship) occurs if the start or finish of one task (the successor task) depends on the start or finish of another task (the predecessor task). For example, if Task B can start when Task A finishes or later, then Task A is a predecessor of Task B with a Finish-to-Start (FS) relationship. Other relationships are SS (Start-to-Start), FF (Finish-to-Finish), and SF (Start-to-Finish). Lag or Lead (negative Lag) can be specified in a relationship to allow the successor to start later or earlier than the original plain relationship. For example, an SF relationship with negative 2 days of lag means that the successor can start 2 days before the predecessor finishes, or later.
A task constraint limits when the task can occur, independent of other tasks. For example, if a task cannot start any earlier than 1/1/2010, then it would have a “Start No Earlier Than” (SNET) type of constraint with a constraint date of 1/1/2010.
The Critical Path Method (CPM) is a method of calculating the total duration of a project based on a specified project start date and on the individual duration of tasks and on their dependencies. CPM also provides useful information about how far a task can slip into the future before it moves other tasks or makes the project finish later.
For a specified project start date and a set of tasks along with their dependencies and constraints, the CPM method calculates the following:
- The earliest date each task can start and finish, and the earliest date the project can finish.
- The latest date each task can start and finish, without causing the project to finish later.
- How far into the future each task can slip without causing any other task to finish later. [those statements are identical!].
- Which tasks are critical, for example, which tasks will cause the project to finish later if they slip.
Before looking at how the CPM works, here are a few related definitions from Microsoft Project Help:
| Task Dependency | A task dependency describes how a task is related to the start or finish of another task. Microsoft Project provides four task dependencies you can use to connect a series of tasks in a schedule. By using these dependencies effectively, you can modify the critical path and shorten your project schedule slack. |
| Lag Time | A delay between tasks that have a dependency. For example, if you need a two-day delay between the finish of one task and the start of another, you can establish a finish-to-start relationship and specify a two-day lag time. You enter lag time as a positive value relationship. |
| Predecessor | A task whose start or finish determines the start or finish of another task. |
| Successor | A task that cannot start or finish until another task starts or finishes. |
| Early Start | The Early Start field contains the earliest date that a task could possibly begin, based on the early start dates of predecessor and successor tasks, and other constraints. Early Start is calculated as follows: When you first create a task, its early start date is the same as the scheduled start date. As you link the task to predecessors and successors and apply any other constraints, Microsoft Project calculates the early start date as the earliest possible date this task could be started, if all predecessor and successor tasks also start on their early start dates. If there is a leveling delay on the task, this is also figured into the early start date. |
| Early Finish | The Early Finish field contains the earliest date that a task could possibly finish, based on early finish dates of predecessor and successor tasks, other constraints, and any leveling delay. |
| Late Start | The Late Start field contains the latest date that a task can start without delaying the finish of the project. This date is based on the task’s start date, as well as the late start and late finish dates of predecessor and successor tasks, and other constraints. |
| Late Finish | The Late Finish field contains the latest date that a task can finish without delaying the finish of the project. This date is based on the task’s late start date, as well as the late start and late finish dates of predecessor and successor tasks, and other constraints. |
| Critical task | A task that must be completed on schedule for the project to finish on time. If a critical task is delayed, the project completion date is also delayed. A series of critical tasks makes up a project’s critical path. |
| Critical path | The series of tasks that must be completed on schedule for a project to finish on schedule. Each task on the critical path is a critical task. Most tasks in a typical project have some slack and can therefore be delayed a little without affecting the project finish date. Those tasks that cannot be delayed without affecting the project finish date are the critical tasks. As you modify tasks to resolve over allocations or other problems in your schedule, be aware of the critical tasks and that changes to them will affect your project finish date. |
| Critical Path Method (CPM) | A project management method of calculating the total duration of a project based on individual task durations and their interdependencies. |
| Slack (or Float) | The amount of time a task can slip before it affects another task’s dates or the project finish date. Slack is sometimes referred to as float time. |
| Free Slack | The amount of time a task can slip before it delays another task. |
| Total Slack | The amount of time a task can slip before it delays the project finish date. When the total slack is negative, the duration for a task is too long for its successor to begin on the date required by its constraint. |
CPM produces results by doing a Forward Pass calculation followed by a Backward Pass calculation:
- Forward Pass: All tasks are calculated to start as early as possible for the specified task dependencies and constraints, and the specified project start date. The latest finishing task(s) determines the project finish date. The Early Start and Early Finish dates for each task are calculated during this pass.
- Backward Pass: All tasks are calculated to finish as late as possible for the specified task dependencies and constraints, and the project finish date calculated from the Forward pass. The Late Start and Late Finish dates are calculated for each task during this pass.
Example
A project starts on 1st October 2016 and every day is a working day. The four columns below are the specified task ID, Duration (in days), Predecessors, and Successors. All the relationships are FS, and there are no other constraints (like Start No Earlier Than).
| ID | Dur. | Pred. | Succ. |
| 1 | 2d | 3 | |
| 2 | 4d | 3 | |
| 3 | 3d | 1,2 | |
| 4 | 2d | 5 | |
| 5 | 3d | 4 |
Forward Pass:
In the table below, the cells filled with the letter “e” show how the task Early Start and Early Finish dates are calculated during the forward pass. Notice that tasks with no predecessors start at the specified project start date (1st Oct), and other tasks are scheduled as early as possible for the specified relationships. The calculated project finish date is 7th Oct.
| ID | Dur. | Pred. | Succ. | Oct 1 | Oct 2 | Oct 3 | Oct 4 | Oct 5 | Oct 6 | Oct 7 | Oct 8 | Oct 9 | Early Start | Early Finish | Free Slack |
| 1 | 2d | 3 | E | E | Oct1 | Oct2 | 2d | ||||||||
| 2 | 4d | 3 | E | E | E | E | Oct1 | Oct4 | 0d | ||||||
| 3 | 3d | 1,2 | E | E | E | Oct5 | Oct7 | 0d | |||||||
| 4 | 2d | 5 | E | E | Oct1 | Oct2 | 0d | ||||||||
| 5 | 3d | 4 | E | E | E | Oct3 | Oct5 | 2d |
Backward Pass:
In the table below, the cells filled with the letter “X” show how the task Late Start and Late Finish dates are calculated during the backward pass. Notice that tasks with no successors start at the project finish date that was calculated during the forward pass (Oct 7), and that other tasks are scheduled as late as possible for the specified relationships.
| ID | Dur. | Pred. | Succ. | Oct 1 | Oct 2 | Oct 3 | Oct 4 | Oct 5 | Oct 6 | Oct 7 | Late Start | Late Finish |
| 1 | 2d | 3 | X | X | Oct3 | Oct4 | ||||||
| 2 | 4d | 3 | X | X | X | X | Oct1 | Oct4 | ||||
| 3 | 3d | 1,2 | X | X | X | Oct5 | Oct7 | |||||
| 4 | 2d | 5 | X | X | Oct3 | Oct4 | ||||||
| 5 | 3d | 4 | X | X | X | Oct5 | Oct7 |
A comparison of the Early and Late dates for a task is used to compute its Total Slack and to determine if the task is critical (Zero Total Slack). From the table below, you can see that the only critical tasks are task 2 and 3, and that they form a single critical path from the start to the end of the project.
| ID | Dur. | Pred. | Succ. | Oct 1 | Oct 2 | Oct 3 | Oct 4 | Oct 5 | Oct 6 | Oct 7 | Total Slack | Critical |
| 1 | 2d | 3 | E | E | 2d | No | ||||||
| X | X | |||||||||||
| 2 | 4d | 3 | E | E | E | E | 0d | Yes | ||||
| X | X | X | X | |||||||||
| 3 | 3d | 1,2 | E | E | E | 0d | Yes | |||||
| X | X | X | ||||||||||
| 4 | 2d | 5 | E | E | 2d | No | ||||||
| X | X | |||||||||||
| 5 | 3d | 4 | E | E | E | 2d | No | |||||
| X | X | X |
More complicated projects can have more than one critical path. In non-classical projects with more advanced features, a project might have no critical path.
A basic knowledge of project planning and management concepts is essential prior to attending a Microsoft Project software training course.