Project scheduling in software engineering

project scheduling in software Engineering

1. Project Scheduling in Software Engineering By KISHORE ADHIKARI DEPT.COMPUTER SCIENCE ASSAM UNIVERSITY SILCHAR

2. SCHEDULING : Scheduling the project tasks is an important project planning activity. It involves deciding which task would be taken up when. The scheduling consists of deciding which tasks would be taken up when and by whom.

3. In order to schedule the project activities, a software project manager needs to do the following:- Identify all the tasks needed to complete the project. Break down large tasks into small activities. Determine the dependency among different activities. Establish the estimates for the time durations needed to complete the project. Allocate resources to the activities. Plan the starting and ending dates for various activities. Determine the critical path. A critical path is a chain of activities that determines the duration of the project.

4. How it works? The first step involves identifying all the tasks needed to complete the project. Next the large tasks are broken down into logical set of small activities which would be assigned to different developers. This is done by the manager by creating a Work Breakdown Structure(WBS) .

5. Next the dependency among the different activities determines the order in which the different activities carried out . D ependency among the activities are represented in the form of an activity network .

6. Once the activity network representation has been done. Resources allocation is typically done using a Gantt chart . After resource allocation is done, a PERT chart is representation is developed.(PERT chart is suitable for project monitoring and control). Milestone : End of the each task is called a milestone.

7. Work Breakdown Structure(WBS) WBS is used to decompose a given task set recursively into small activities . The root of the tree is labelled by the problem name . Each node of the tree is broken down into smaller activities . Each activity is recursively decomposed into smaller sub activities, until at the leaf level, the activities require approximately 2 weeks to develop .

8. An example of WBS of an MIS problem.

9. Activity Network An activity network shows the different activities making up a project, their estimated durations, and their interdependencies. In this representation, each activity is represented by a rectangular node and the duration of the activity is shown alongside each task in the node.

10. Activity network representation of the MIS problem

11. Critical Path Method(CPM): Critical path is the sequence of Critical Activities in a network. A network diagram may have more than one critical paths. It is the largest path in a network. Critical path gives the minimum time required to complete a project. The activities in the critical path are called critical activities . If the critical activities are delayed, then the project is also delayed.

12. From the network diagram, following analysis can be made: Minimum Time (MT): to complete the project is maximum of all paths from start to finish. Earliest Start Time (ES): is the maximum of all paths from start to this task . Earliest Finish Time (EF): of a task is the sum of the ES of the task and its duration . Latest Start Time (LS): is the difference between MT and maximum of all paths from this task to finish. Latest Finish Time (LF): of a task can be obtained by subtracting maximum of all paths from this task to finish from the MT. Slag Time (ST): is LS-ES and LF-EF

13. MIS problem with (ES,EF)

14. MIS problem with (LS,LF )

15. From the above diagram: Critical task is the one with slack time =

16. Gantt Chart Gantt chart has been named after its developer Henry Gantt. A Gantt chart is a form of bar chart. In the Gantt charts each bar consists of a unshaded part and a shaded part . The shaded part of the bar shows the length of time each task is estimated to take . The unshaded part shows the slack time or lax time . Gantt charts are useful for resource planning. The different types of resources that need to be allocated to activities include staff, hardware, and software.

17. Gantt chart representation of the MIS problem

18. PERT Charts: Project Evaluation & Review Technique . Is a technique for estimating and planning a project. One of its most powerful concepts is that project management is the management of probabilities .

19. Thus, in a PERT chart, instead of making a single estimate for each task, three estimates are made : Optimistic (O) Most Likely(M) Worst case (W) These three estimates are combined to calculate an expected duration . Expected Duration (E)= O + 4*M + W 6

20. PERT chart representation of the MIS problem. Expected Duration of this project = 423.17 Expected Duration of Critical path = 241.16

21. THANK YOU