Project Scheduling

Project scheduling is concerned with the techniques that can be employed to manage the activities that need to be undertaken during the development of a project.

Scheduling is carried out in advance of the project commencing and involves:

•    identifying the tasks that need to be carried out;

•    estimating how long they will take;

•    allocating resources (mainly personnel);

•    scheduling when the tasks will occur.

Once the project is underway control needs to be exerted to ensure that the plan continues to represent the best prediction of what will occur in the future:

•    based on what occurs during the development;

•    often necessitates revision of the plan.

Effective project planning will help to ensure that the systems are delivered:

•    within cost;

•    within the time constraint;

•    to a specific standard of quality.

Two project scheduling techniques will be presented, the Milestone Chart (or Gantt Chart) and the Activity Network.

Milestone Charts

Milestones mark significant events in the life of a project, usually critical activities which must be achieved on time to avoid delay in the project.

Milestones should be truely significant and be reasonable in terms of deadlines (avoid using intermediate stages).

Examples include:

•    installation of equipment;

•    completion of phases;

•    file conversion;

•    cutover to the new system

Gantt Charts

A Gantt chart is a horizontal bar or line chart which will commonly include the following features:

•    activities identified on the left hand side;

•    time scale is drawn on the top (or bottom) of the chart;

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•    a horizontal open oblong or a line is drawn against each activity indicating estimated duration;

•    dependencies between activities are shown;

•    at a review point the oblongs are shaded to represent the actual time spent (an alternative is to represent actual and estimated by 2 separate lines);

•    a vertical cursor (such as a transparent ruler) placed at the review point makes it possible to establish activities which are behind or ahead of schedule.



Activity Networks

The foundation of the approach came from the Special Projects Office of the US Navy in 1958. It developed a technique for evaluating the performance of large development projects, which became known as PERT - Project Evaluation and Review Technique. Other variations of the same approach are known as the critical path method (CPM) or critical path analysis (CPA).

The heart of any PERT chart is a network of tasks needed to complete a project, showing the order in which the tasks need to be completed and the dependencies between them. This is represented graphically:



EXAMPLE OF ACTIVITY NETWORK

The diagram consists of a number of circles, representing events within the development lifecycle, such as the start or completion of a task, and lines, which represent the tasks themselves. Each task is additionally labelled by its time duration. Thus the task between events 4 & 5 is planned to take 3 time units. The primary benefit is the identification of the critical path.

The critical path = total time for activities on this path is greater than any other path through the network (delay in any task on the critical path leads to a delay in the project).

Tasks on the critical path therefore need to be monitored carefully.

The technique can be broken down into 3 stages:

1. Planning:

•    identify tasks and estimate duration of times;

•    arrange in feasible sequence;

•    draw diagram.

2. Scheduling:

•    establish timetable of start and finish times.

3. Analysis:

•    establish float;

•     evaluate and revise as necessary