Scheduling Techniques & Project Management

Project management is the process by which a proposed project is developed within a rigorous framework. The subset of project management that this lecture will focus on is 'project scheduling', that is the process by which the various activities that need to be undertaken during a projects lifetime should be scheduled. There are a range of activity management tools that are commercially available.

1. 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.

2. 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.

2.1 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;
• 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.

Project management tools incorporating Gantt Charts include PRINCE [CCTA, 1990], MacProject and Microsoft Project.

Example of a Gantt Chart:

Figure 1: Example of a Gantt Chart

Which tasks is ahead of schedule ? Which task is behind schedule ?

Alternative Gantt Chart incorporating features commonly present in automated tools:

Figure 2: Example of a Gantt Chart showing Project Management Tool Features

Gantt charts produced in this form are:

• graphical;
• easy to read;
• easy to update.

There are no widely accepted standards for Gantt charts. Automated tools are available which produce Gantt charts directly from activity networks or from a full definition of the tasks.

Automated tools have features which assist the planning function including:

• display of original and latest time for task;
• display of person(s) allocated to tasks;
• integration with other planning techniques (i.e. networks and milestones).

Now try to create a Gantt chart from the information presented in the Gantt Chart tutorial.

3. 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:

Figure 3: Example of an 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.

3.1 Diagram Symbols

Figure 4: Symbols Used in Activity Networks

3.2 To Produce the Diagram

1. There is a single start and end event;
2. Time flows from left to right (so does the numbering sequence);
3. Events are given a unique number (activities then have a unique label i.e. head & tail event numbers);
4. The network can then be drawn taking into account the dependencies identified;
5. Working from the start event forward, calculate the earliest times, setting the earliest time of the first event to zero. Add the job duration time to the earliest event time to arrive at the earliest time for the successor event. Where the successor has more than one activity dependent on to the latest time is entered;
6. Working from the finish event backwards, calculate the latest times. Set the latest time to the earliest time for the finish event. Subtract job duration from the latest time to obtain predecessor latest event times. Where the predecessor event has more than one arrow emanating from it enter the earliest time;
7. Event slack is calculated by subtracting the earliest event time from the latest event time;
8. Critical path(s) are obtained by joining the events with zero event slack.

3.3 Worked Example

List of activities for the network:

       Task              Location          Dependent On          Duration       



         A                                       -                   3          



         B                                       -                   6          



         C                                       -                   3          



         D                                       A                   5          



         E                                       C                   2          



         F                                    B, D, E                6          



         G                                       A                   9          

Calculation of Earliest Time:

Use the instructions presented in section 3.2 and the the following diagram ..

Figure 5: Calculation of Earliest Start Time

What is the earliest time for event 4 ? If you are unsure, the answer is explained here.

What is the earliest time for event 5 ? If you are unsure, the answer is explained here.

Calculation of Latest Time:

Use the instructions presented in section 3.2 and the the following diagram ..

Figure 6: Calculation of Latest Start Time

What is the latest time for event 2 ? If you are unsure, the answer is explained here.

What is the latest time of event 1 ? If you are unsure, the answer is explained here.

Drawing the Critical Path:

Figure 7: Drawing the Critical Path

Analysis of the network allows the 'float' to be calculated, this is essentially the amount of time an action can be delayed without delaying the overall project.

Activities on the critical path must be monitored very carefully. Now try the Activity Network tutorial.