Scheduling in project management

Scheduling is one of the most critical activities in project management. Project scheduling involves in separating the total work involved in the project into manageable activities. Project schedules are usually represented as set of charts that includes work breakdown, activities dependencies and staff allocations.  There are two types of tools used to illustrate project schedules. They are bar charts and activity networks.

Bar charts: According to sommerville (2009), Bar charts show who is responsible for each activity and when the activity is schedule to begin and end.  Gantt chart is a bar chart which provides comparative illustration between actual performance and planned performance Gantt chart has been continuously evolved to cope up with the new improvement in project management and techniques. One important modification that forms a link in the evolution of the Gantt chart into PERT/CPM network is called Milestone system. According to Mishra (2005), milestones are key points or events in time that can be identified when completed as the project progresses. They act as reference points for the management.Even though this approach has many advantages, it has its own disadvantages too. They are the following:

•  Bar chart becomes too cumbersome while dealing with complex and big projects when considered in detail and efforts were to find out interaction/ interdependence. 
•  It does not show continuing interrelationship of activities and also it does not tell tolerance in activity times.

The above drawbacks lead to a new scheduling technique called network scheduling. Mishra (2005) says network is a pictorial representation of the inter relationships among all activities in the project. Network activity diagram is drawn after identifying project activities. Next step is to assign expected time duration to the activities. . The expected duration depends on the planned team size work method equipment and working hours. A particular level of resource must be assumed to be available when the work is to be performed.  The following are the advantages of network scheduling identified by Mishra (2005). They are:

• They lead to planning a project to the selected level of details so that all parts of the project and their intended order of accomplishment are known. 
•  They provide a fairly accurate estimate of the length of time it will take to complete the project and the activities that must be kept on time to meet the schedule. 
•  They provide a graphical picture and standardized vocabulary to aid in understanding work assignments and communicating among people involved in the project. 
•  They provide a means to track progress on a project (that is, show where work is with respect to the plan). 
•  They identify and focus attention on potentially troublesome activities to facilitate management by exception. 
•   They provide a means of estimating the time and cost impact of changes in the project

There are two types of network conventions used to draw a network diagram they are Activity-on-Node (AON) convention and Activity-on- Arrow (AOA). AON is where circles are used to represent an activity, with arrows linking them together to show the sequence in which they are performed. . An alternative is to show the activities as arrows and use circles to connect predecessor and successor activities. This method is called the activity on-arrow (AOA) convention.