Chapter 5 - Planning and Scheduling

Question 1

What must a project plan be able to do?

Answer 1

1. define the tasks that need to be carried out as part of the processes that are being followed; 2. the duration and dependencies for each task;
2. the people and physical resources required by each task
3. the milestones or goals of each task.

Question 2

What are some things that can go wrong when making a project plan?

Answer 2

• Unrealistic deadlines typically established by someone outside of the project team and forcing the schedule on the project team.
• Changing requirements that are not reflected in the project plan.
• Honest underestimates of effort and the amount of resources required to complete the project.
• Risks that were either predictable or unpredictable at the start of the project but not accounted for in the project plan.
• Technical difficulties that could not have been foreseen at the start of the project.
• Human difficulties that could not have been foreseen at the start of the project.
• Failure to see slippage and for the project management to see that the project is falling behind schedule.
• Miscommunication between project staff causing delays.

Question 3

What are the basic principles of project planning?

Answer 3

1. Compartmentalise
2. Interdependency
3. Time Allocation
4. Effort Validation
5. Defined Responsibilities
6. Defined Outcomes
7. Defined Milestones

Question 4

Explain the compartmentalise principle of project planning.

Answer 4

The aim here is to decompose the project until the activities, actions and tasks are manageable. The basis for accomplishing this decomposition is typically to decompose both the product and the process.

Question 5

Explain the Interdependency principle of project planning.

Answer 5

The interdependencies between activities, tasks and actions need to be determined. De- pendencies can take a number of forms. Tasks may be sequentially dependent on each other, for example, when one task must use the work product produced by another task, or when the purpose of one task is to establish some ground conditions for another task. One the other hand, if there are no dependencies between tasks then they may occur in parallel.

Question 6

Explain the Time Allocation principle of project planning.

Answer 6

This is one of the harder tasks in project planning. An estimate of the number of resources or effort — for example, person days — must be included for each task in the plan. Then, the start date and completion date, based on the interdependencies, and whether or not the work will be completed on a part-time or full-time basis needs to be estimated.

Question 7

Explain the Effort Validation principle of project planning.

Answer 7

The number of people and resources on a project are typically finite. Validation is the management activity of going through the project plan to ensure that only the available

Question 8

Explain the Defined Responsibilities principle of project planning.

Answer 8

Every scheduled task should be assigned to a specific team member.

Question 9

Explain the Defined Outcomes principle of project planning.

Answer 9

Every scheduled task should have a well defined outcome. The outcomes for software
engineering tasks are typically work products or parts of work products.

Question 10

Explain the Defined Milestones principle of project planning.

Answer 10

Every task or group of tasks is associated with a defined milestone. Milestones are accomplished in the project plan when a work-product or group of work-products are accepted for further development.

Question 11

When can the project schedule be shortened by adding more resources?

Answer 11

When there is no communication between the workers (e.g. picking cotton)

Question 12

Define man-months

Answer 12

the number of months it would take a person to complete a task

Question 13

What is a pitfall of using man-months to estimate project duration?

Answer 13

can be misleading. A task that takes ten months for a single person is unlikely to take one month for ten people.

Question 14

How can adding more people to a project that is already behind schedule go wrong?

Answer 14

• can cause delays due to unfamiliarity with the system
• noobs must learn the system - h takes people off the project to help the new people, and the project falls even further behind.
• as new people are added the number of communication channels increases and so may slow the work down even more.

Question 15

What is the work breakdown structure?

Answer 15

The principle of compartmentalisation requires that we break this high-level set of tasks down into more manageable tasks. The task breakdown can be done using a diagram and this results in a tree-like structure called the work breakdown structure.

Question 16

Define the 100% rule regarding the work breakdown structure.

Answer 16

The 100% rule states that the work breakdown structure includes 100% of the work defined by the project scope
and captures all deliverables — internal, external, and interim — in terms of the work to be completed, including all project management.
as new work-packages are identified then they must all be built into the existing work breakdown structure and into the project plan.

Question 17

Why might dependencies exist between tasks?

Answer 17

• A task relies on a work product produced by another task; for example, the design task needs a requirements specification produced by the requirements task.
• A task relies on a work product (developed by another task) to be in a specific state before it can commence; for example, requirements and design may be done in parallel but the design task relies on the shared specification to be at a baseline.
• A task needs the resources used by another task.

Question 18

What is a task network?

Answer 18

The result of analysing all of the dependencies.

Question 19

What does PERT stand for?

Answer 19

Program Evaluation and Review Technique

Question 20

What is the difference between a PERT chart and a Gantt chart?

Answer 20

• A Gantt chart presents the same kind of information as a PERT chart
• Gantt chart shows the duration of each activity against calendar time, which PERT charts do not.
• Gantt charts are a tabular representation of the project schedule, so they can be used to present a large amount of information in a relatively compact form.

Question 21

What is a milestone?

Answer 21

A milestone is an event that takes zero time. It is often used to represent the completion of an activity or the delivery of work-product.

Question 22

What is an activity?

Answer 22

An activity is part of a project that requires resources and time.

Question 23

What is free float or free slack?

Answer 23

The free float or free slack is the amount of time that a task can be delayed without causing a delay to subsequent tasks. The total slack or total float is the amount of time that a task can be delayed without delaying project completion

Question 24

What is the critical path?

Answer 24

The critical path is the longest possible continuous path taken from the initial event to the terminal event. It determines the total calendar time required for the project; and, therefore, any time delays along the critical path will delay the reaching of the terminal event by at least the same amount.

Question 25

What is the critical activity?

Answer 25

A critical activity is an activity that has total float equal to zero. Activities with zero float are not necessarily on the critical path.

Question 26

What is a PERT chart?

Answer 26

• represents the project schedule as an activity network
• estimates project durations by decomposing the project into tasks and dependencies
• ideal for the early stages of project planning

Question 27

What do nodes and edges in a PERT chart represent?

Answer 27

Each node in the network is a model of the project task taken from the work breakdown structure.
Edges in the network model dependencies between tasks.

Question 28

In which cases is a PERT chart ideal?

Answer 28

PERT is ideal for the situations in which there is uncertainty because it makes use of (bounded) uncertainty in the duration tasks as part of the analysis.

Question 29

What is a predecessor node in a PERT chart?

Answer 29

A predecessor node is a node that immediately precedes some other node without any other nodes intervening. It may be the consequence of more than one activity.

Question 30

What is a successor node in a PERT chart?

Answer 30

A successor node is a node that immediately follows some other node without any other nodes intervening. It may be the consequence of more than one activity.

Question 31

What is the optimistic time in a PERT chart?

Answer 31

The optimistic time (O) is the minimum possible time required to accomplish a task, assuming everything pro- ceeds better than is normally expected.

Question 32

What is the pessimistic time in a PERT chart?

Answer 32

The pessimistic time (P) is the maximum possible time required to accomplish a task, assuming everything goes wrong (but excluding major catastrophes).

Question 33

What is the most likely time in a PERT chart?

Answer 33

The most likely time (M) is the best estimate of the time required to accomplish a task, assuming everything proceeds as normal.

Question 34

What is the expected time in a PERT chart?

Answer 34

The expected time (TE) is the average time the task would require if the task were repeated on a number of occasions over an extended period of time. Expected time is estimated by the formula:
TE = (O+4M+P)/6

Question 35

What time estimates need to be calculated in the PERT chart?

Answer 35

• Earliest start time (ES),
• Latest start time (LS),
• Earliest finish time (EF)
• Latest finish time (LF)
• Slack time

Question 36

How does one calculate the earliest start and finish times?

Answer 36

forward pass through the network
Step 1 Estimate the expected time of all of the tasks in the activity network. Ideally, you will need to build up some history of projects and the times that specific tasks took to complete so that you can make better estimates.
Step 2 Start by selecting all of the activities with no dependencies. The earliest start time for each of these is day 0. The earliest finish time for each of these is their duration.
Step 3 Next identify all of the successor nodes to those identified in the previous step.
If a node has a single predecessor then its earliest start time is equal to the earliest finish time of its predecessor.
If a node has multiple predecessor nodes then its earliest start time is equal to the maximum earliest finish time of all of its predecessors.
Step 4 Repeat Step 3 until there are no more activities left.

Question 37

How does one calculate the duration of a task in the PERT chart?

Answer 37

If we use the most likely time then the estimate may be too low if some tasks take their pessimistic time to complete. If we use pessimistic times for the duration of a task then our estimate may be too long and we may find ourselves costing the project too high. If we take only the optimistic times then we may end up under-pricing our project and so lose money. There is no right answer for this — project managers rely on their experience to determine which time to use for different projects.

Question 38

How does one calculate the latest start and finish times in a network?

Answer 38

• by a backwards pass through the network
• use the expected time as the duration for the task.
  Step 1 Start by identifying the activities with no successor nodes. The latest finish time for each of these is final day of the project. The latest start time for each of these is their latest finish time minus their duration.
  Step 2 Next identify all of the predecessor nodes to those identified in the previous step.
  If a node has a single successor then its latest finish time is equal to the latest start time of its successor.
  If a node has multiple predecessor nodes then its latest finish time is equal to the minimum latest start time of all of its successors.
  Step 3 Repeat until there are no more activities left.

Question 39

How do you calculate the free slack?

Answer 39

The free slack is calculated as LF - EF.

Question 40

What is a common mistake when making Gantt charts?

Answer 40

A common mistake is that Gantt charts are actually used to create a project design and that they define work breakdown structure. This is not the case. We have stressed that process design is about choosing a set of processes to meet a goal and the work breakdown structure defines the tasks that need to be done as part of the process. Gantt charts simply represent this design as a project schedule.

Question 41

What do and don’t Gantt charts focus on?

Answer 41

Gantt charts only focus on schedules and not on scope or cost. They can however be used show dependencies and resources as well as the progress of the project against calendar time.

Question 42

What is the critical path?

Answer 42

The critical path is the path with the longest duration. The overall duration of the critical path estimates the total time that project will take. All activities on the critical path have a free slack of 0. Any delay in starting or finishing an activity on the critical path will delay the total completion time of the project.

Question 43

Why would you want to add extra resources to the critical path?

Answer 43

• remove some of the dependencies between activities on the critical path; or
• shorten the durations of the activities on the critical path — but we must be mindful of the Putnam-Norden-
Rayleigh curves.

Question 44

How can a project manager track the progress of a project?

Answer 44

• Period reviews where team members report progress.
• Evaluating the results of reviews and audits conducted as part of the software engineering process.
• Determining whether formal project milestones have been accomplished by the scheduled data.
• Comparing actual start dates with scheduled start dates.
• Meeting informally with the engineers working on the project to get their subjective assessments of progress and upcoming problems.
• Using a formal method like earned value analysis [Pre09].

Question 45

How is planning done in agile development?

Answer 45

• Plan short iterations: Using shorter iterations give the team a measurable progress indicator. Functionality is delivered on a regular basis.
• Produce useful functionality: Each iteration should produce a useful piece of functionality; for example, one requirement.
• Using “Just in time” (JIT) planning: Only plan for iterations that will be starting in the near future.
• Use the team: All members of the team should be involved in both the scheduling and the assignment of word to team members. Not only does this promote a sense of belonging, but the team will have to implement the plan, so are motivated to get it right. Furthermore, they know their strengths and preferences, so involving them in the planning ensures that they do the work they want — within reason!.

Question 46

How do Gantt and PERT charts fit into agile development?

Answer 46

• have little use in agile planning, even at the iteration level
• Instead having a list of the tasks that must be completed is highly valuable, and relatively lightweight.
• Gantt charts can be used to track dependencies between tasks.

Question 47

When don’t you want to use agile?

Answer 47

• agile projects work effectively on small-to-medium scale systems, assuming that the same techniques will work for embedded systems that control aircraft missile systems or air traffic is off the mark.
• For systems in which safety, reliability, and security are important factors, an agile approach is less likely to be effective, because the requirements of these products really do need to be carefully planned, as to the projects that build them.
• Agile projects are also less suitable for teams who are geographically separated. Agile methodologies typically promote teams working closely together on small tasks, and aim to minimise documentation. However, for a team that is separated over different locations, this model does not work as effectively. While techniques have been proposed to mitigate this problem, such as getting agile teams together for 1-2 months at the start of the project, these are costly overheads for some organisations.