SCHEDULING

4.3 SCHEDULING

The scheduling activity at Infosys can be broken into two subactivities: determining the overall schedule (the project duration) with major milestones, and developing the detailed schedule of the various tasks.

4.3.1 Overall Scheduling

As discussed earlier in the chapter, you can gain some flexibility in determining the schedule by controlling the staffing level, but this flexibility is limited. Because of this possible flexibility, building strict guidelines for scheduling may not be desirable; strict guidelines forfeit the advantage of the flexibility to be passed to the project or the customer. Furthermore, the project schedule is usually determined in the larger context of business plans, which impose some schedule requirements. Whenever possible, you should exploit your schedule flexibility to satisfy such requirements. One method is to use scheduling guidelines more for checking the feasibility of the schedule than for determining the schedule itself.

Figure 4.2 shows the scatter plot of the schedule and effort for some of the completed development projects at Infosys, along with a nonlinear regression curve fit for the scatter plot.

Figure 4.2. Schedule as a function of effort

graphics/04fig02.gif

The equation of the curve in Figure 4.3 is

schedule = 23.46 (effort)0.313

Figure 4.3. Manpower ramp-up in a typical project

graphics/04fig03.gif

From the distribution of the points, it is evident that schedule is not a function solely of effort. The determined schedule can, however, be used as a guideline or check of the schedule's reasonableness, which might be decided based on other factors. Similarly, the schedule and effort data from similar projects can be used to check the reasonableness of any proposed schedule.

Project managers often use a rule of thumb, called the square root check, to check the schedule of medium-sized projects. The principle is that the proposed schedule should be around the square root of the total effort in person-months; the schedule can be met if graphics/04infig01.gifresources are assigned to the project. For example, if the effort estimate is 50 person-months, a schedule of about 7 to 8 months will be suitable with about 7 to 8 full-time resources.

Because of the relationship between schedule and resources, a schedule is accepted only if the head of the business unit to which the project belongs agrees to provide the necessary resources. If the necessary resources are not available, the schedule must be adjusted. Dependencies of the project are also checked before a schedule is accepted. If the project execution depends on external factors (such as completion of another project or availability of certain software), the schedule must be adjusted to accommodate these factors.

Once the overall duration of the project is fixed, the schedule for the major milestones must be determined. To determine the milestones, you must first understand the manpower ramp-up that usually takes place in a project. The number of people in a software project tends to follow the Rayleigh curve.9,11 In the beginning and the end, few people work on the project; the peak team size (PTS) is reached somewhere near the middle of the project. This behavior occurs because only a few people are needed in the initial phases of requirements analysis and design. The human resources requirement peaks during coding and unit testing. Again, during system testing and integration, fewer people are required. In many cases, the staffing level does not change very often, but approximations of the Rayleigh curve are used: assigning a few people at the start, having the peak team during the build phase, and then leaving a few people for integration and system testing. If you consider design, build, and test as three major phases for which requirements are done, the manpower ramp-up in projects typically resembles the function shown in Figure 4.3

At Infosys, this approach for assigning resources is generally followed. Fewer people are assigned to the starting and ending phases, with maximum people during the build phase. During the build phase, the PTS for the project is usually achieved.

For ease of scheduling, particularly for smaller projects, all the required people are often assigned together around the start of the project. This approach can lead to some people being unoccupied at the start and toward the end. This slack time is often used for training. Project-level training is generally needed in the technology being used and the business domain of the project, and this training consumes a fair amount of effort, as can be seen in the effort distribution given in the PCB. Similarly, the slack time available in the end can be utilized for documentation and other closure tasks.

The schedule distribution differs from the effort distribution. For these three major phases, the percentage of the schedule consumed in the build phase is smaller than the percentage of the effort consumed because this phase involves more people. Similarly, the percentage of the schedule consumed in the design and testing phases exceeds their effort percentages. The exact schedule depends on the planned manpower ramp-up. Given the effort estimate for a phase, you can determine the duration of the phase when you know the manpower ramp-up.

Generally speaking, design requires about 40% of the schedule (20% for high-level design and 20% for detailed design), build consumes about 40%, and integration and system testing consume the remaining 20%. The manpower ramp-up typically is around 1:2:1 for design, build, and integration and testing, respectively (giving an effort distribution among these phases as 1:4:1). These types of guidelines provide a check for the milestones, which can be set based on other constraints.

It is important to recognize that even a person assigned full time to a project typically performs other tasks that consume time but do not contribute to the project. These tasks include leave, corporate activities, general (not project-specific) training, reviews in other projects, and so on.

4.3.2 The Effectiveness of the Approach

As with effort estimates, one way of checking the schedule estimates is to plot the actual schedule against the estimated schedule and see how close the points are to the 45-degree line. If all the points fall very close to the 45-degree line, the scheduling approach can be considered effective. Figure 4.4 shows this plot for previously completed development projects.

Figure 4.4. Actual versus estimated schedule

graphics/04fig04.gif

As you can see, the scheduling approach results in schedules that match reasonably well with the actual schedule. Keep in mind, however, that other factors (discussed in section 4.2) may determine whether the estimated schedule is met.

4.3.3 Detailed Scheduling

Once the milestones and the resources are fixed, it is time to set the detailed scheduling. The project manager breaks the tasks into small schedulable activities in a hierarchical manner. For each detailed task, the project manager estimates the time required to complete it and assigns a suitable resource so that the overall schedule is met. In assigning resources, she considers various factors such as leave plans of the team members, their personal growth plans and career paths, their skill sets and experience, training and mentoring needs, the criticality of the task, and the future value that the experience acquired in a task may provide to the project.

At each level of refinement, the project manager checks the effort for the overall task in the detailed schedule against the effort estimate. If necessary, she adjusts the detailed estimates. For example, she will break down the detailed design phase into tasks such as developing the detailed design for each module, review of each detailed design, fixing of defects found, and so on, and she may break down each of these further. Then she schedules these activities and assigns resources for some duration.

If this detailed schedule is not consistent with the overall schedule and effort estimate for detailed design, she must change the detailed schedule. If she finds that the best detailed schedule cannot match the milestone effort and schedule, she must revise the earlier estimates. Thus, scheduling is an iterative process.

Generally, the project manager refines the tasks to a level so that the lowest-level activity can be scheduled to occupy no more than a few days from a single resource. She also adds general activities, such as project management, coordination, database management, and configuration management. These activities have less direct effect on the schedule because they are ongoing tasks rather than schedulable activities. Nevertheless, they consume resources and hence are included in the project schedule.

Rarely does the project manager complete the detailed schedule of the entire project all at once. Once the overall schedule is fixed, she may do the detailing for a phase only at the start of that phase.

For detailed scheduling, project managers frequently use Microsoft Project (MSP) or a spreadsheet. For each lowest-level activity, they stipulate the effort, duration, start date, end date, and resources. For each activity, they also specify the activity code (discussed further in Chapter 7), the program code, and the module code. They may also specify dependencies between activities, due either to an inherent dependency (for example, you can conduct a unit test plan for a program only after it has been coded) or to a resource-related dependency (the same resource is assigned two tasks).

A detailed project schedule is never static. Changes may be needed because the actual progress in the project may be different from what was planned, because newer tasks are added in response to change requests, or because of other unforeseen situations. Changes are done as and when the need arises.

The final schedule, as recorded in MSP or some other tool, is the most "live" project plan document. During the project, if plans must be changed and additional activities must be done, after the decision is taken, any changes are reflected in the detailed schedule. Hence, the detailed schedule becomes the main document that tracks the activities and schedule. The detailed schedule is also a key input in project monitoring, which is discussed in Chapter 11.

4.3.4 The Schedule of the ACIC Project

Let's consider the example of the ACIC project. (See my earlier book for the scheduling of a different case study.10) As discussed earlier, the effort estimates for the ACIC project were 501 person-days, or about 24 person-months. The customer gave approximately 5.5 months to finish the project (from May 15 to November 3). Because this is more than the square root of effort in person-months, and because requirement gathering had to be finished before the project started, this schedule was accepted. (The resource requirement for this schedule was also estimated and is given in the project management plan in Chapter 8.)

The milestones are determined by using the effort estimate for the phase and an estimate of the number of resources that can be fully occupied in this phase. In the ACIC project, the project manager listed the major activities in each phase and assigned them to resources. From this assignment, he determined the overall schedule and effort for the phase. If the total effort for the phase did not match the effort estimate, he revised the assignment until the total effort matched the effort estimate. Then the overall schedule, as obtained from the assignment of activities, was taken as the schedule for the phase. (The milestones are specified in the project management plan given in Chapter 8.) Table 4.8 shows the high-level schedule of the ACIC project. This schedule is obtained automatically from the final detailed schedule of the project.

In the table, the task ID is the sequence number assigned in the MSP. The task IDs show that the total number of tasks in the final schedule was more than 330 and that each of these high-level tasks had many schedulable activities under it. The first task was the overall project, with a duration of about 140 days and an effort of 560 person-days. (This schedule is from the final schedule of the project, which incorporated the changes to be done; the final two tasks in this table are the two major changes.)

Table 4.8. High-level Schedule for the ACIC Project

Task ID

Task

Duration (days)

Work (person-days)

Start Date

End Date

1

ACIC development schedule

139.56

559.93

4/3/00

11/3/00

2

Project initiation activities

33.78

24.2

5/4/00

6/23/00

29

Regular activities

87.11

35.13

6/5/00

10/16/00

74

Training

95.11

49.37

5/8/00

9/29/00

99

Organization activities

76.89

12.9

5/22/00

9/15/00

104

Knowledge sharing initiative

78.22

19.56

6/2/00

9/30/00

110

Inception phase activities

26.67

22.67

4/3/00

5/12/00

114

Elaboration Iteration 1

27.56

55.16

5/15/00

6/23/00

157

Elaboration Iteration 2

8.89

35.88

6/26/00

7/7/00

198

Construction Iteration 1

8.89

24.63

7/10/00

7/21/00

228

Construction Iteration 2

6.22

28.22

7/20/00

7/28/00

256

Construction Iteration 3

6.22

27.03

7/31/00

8/8/00

290

Transition phase activities

56

179.62

8/9/00

11/3/00

323

Window resized release of 2.0 code

26.67

39.11

8/14/00

9/22/00

331

Back-end mainframe work for 3.0

4.44

6.44

8/14/00

8/18/00

This high-level schedule is not suitable for assigning resources and detailed planning. During detailed scheduling, these tasks are broken into schedulable activities. In this way, the schedule also becomes a checklist of tasks for the project. As mentioned before, this "exploding" of top-level activities is not done fully at the start but rather takes place many times during the project.

Table 4.9 shows part of the detailed schedule of the construction-iteration 1 phase of the ACIC project. For each activity, the table specifies the module, the program, and the activity code, along with the duration, effort, and so on. The Module and Program columns represent the module and program on which work is being done. Activity Code represents the activity being performed. (The standard organization-wide activity codes are discussed further in Chapter 7.)

Sometimes, the predecessors of the activity (the activities upon which the task depends) are also specified, although they are omitted here. This information helps in determining the critical path and the critical resources.

For each task, how much is completed is given in the % Complete column. This information is used for activity tracking, which is discussed further in Chapter 11. The detailed schedule also specifies the resource to which the task is assigned.

The activity number has been omitted from Table 4.9. As Table 4.8 indicated, there were more than 330 line items in the final schedule of the ACIC project, the lowest-level tasks being the schedulable tasks.

 



Software Project Management in Practice
Linux Annoyances for Geeks: Getting the Most Flexible System in the World Just the Way You Want It
ISBN: 0596008015
EAN: 2147483647
Year: 2005
Pages: 83
Authors: Michael Jang

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