Lecture Note 4 Managing Analysis and Design Activities

Systems Analysis and Design

Kendall & Kendall

Sixth Edition

Part I: System Analysis Fundamentals

CS206 System Analysis & Design Note 3 By ChangYu

2

Major Topics • Project initiation• Determining project feasibility

– Technical feasibility– Economic feasibility– Operational feasibility

• Project scheduling• Managing project activities• Manage systems analysis team

members

Those are all important capabilities for the system analyst to master. They are considered Project Fundamentals.

3

Activity Planning and Control

• Activity planning includes:• Selecting a systems analysis team.• Assign members of the team to appropriate (洽當 ) projects.• Estimate (估計 ) the time required to complete each task.• Schedule (計劃 ) the project so that tasks are completed in a timely

fashion.

• Control means:• Using feedback to monitor (監視 ) the project.• Comparing the plan for the project with its actual evolution (進化 ).

• Expedite (加快 ) / reschedule activities to finish on time, while motivating team members to complete the job properly.

• Two tools for project planning and control are• Gantt charts • PERT diagrams.

These two charts are used to determine the sequence (次序 ) of the activities and precedence (優先 ) relationships among all activities.

4

Step 1: Project is broken down into phases.

Step 2: Further project is broken down into tasks or

activities.

Project Planning and Scheduling:

5

Step 3: Finally project is broken down into steps or even smaller units so that planning and scheduling can take place.Step 4: Time is estimated for each task or activity.

Step 5: Drawing a Gantt chart or PERT diagram to scheduling activities.

6

Estimating Time• Determining time estimates and calculate the

expected completion time for each activity. Three estimates are used

1. Optimistic (樂觀的 ) time (o): Estimates the minimum possible periods of time for an activity to be completed.

2. Pessimistic ( 悲觀的 ) time (p) : Estimates the maximum possible periods of time for an activity to be completed.

3. Realistic (現實的 ) time (r): Estimates the project manager’s “best guess” of the amount of time the activity will require for completion.

7

Expected (期望的 ) time (ET) could be calculated by the following formula:

Where 1, 4, 1 are default weights used to calculated a weighed average of the three estimates.

The example of estimated time calculation and the sequence of activities within a project:

( 4 + 4 * 8 +12 ) / 6 = 8

8

Gantt Chart For Project Scheduling

Project managers plan the project using graphical and textual reports. It shows activities or tasks over a period of time.

Advantages:

• Is easy to use and lends itself to worthwhile communication with end users.

• The bars representing activities or tasks are drawn to scale, that is , the size of the bar indicates the relative length of time it will take to complete each task.

9

PERT Diagram

PERT-Program Evaluation and Review Technique

– PERT is useful when activities can be done in parallel rather than in sequence. (Especially when some team members can be working on certain activities at same time that fellow (同事 ) members are working on other tasks.)

– Once a diagram is drawn it is possible to identify the critical path, the longest path through the activities.

– Monitoring critical (關健的 ) path will identify shortest time to complete the project.

10

• The activities expressed as bars in Gantt chart are represented by arrows in the PERT diagram. The length of the arrows has no direct relationship with the activity durations.

• The activity’ name and duration are presented on the arrows.

• Circles on the PERT diagram are called events and can be identified by numbers, letters, or any other arbitrary (任意的 ) form of designation.

• The circle notes are present to recognize that an activity is completed and indicate which activities need to be completed before a new activity may be undertaken.

• If you are delayed one day on path 10-20-40-50 (critical path), the entire project will take longer, but if you are delayed one day on path 10-30-40-50 , the entire project will not suffer.

11

Occasionally, PERT diagrams need pseudo-activities, referred to as dummy activities, to preserve the logic of or clarify the diagram.

• Project 1 and Project 2 are quit different and the way the dummy is draw makes the difference clear.

• In Project1 activity C can only be started if both A and B are finished. Project1 takes 14 days to complete. The dummy in project1 is necessary.

• In Project2 activity C requires only activity B’s completion and can therefore be under way while activity A is still taking place. Project2 takes only 9 days. The dummy in Project2 is not required and activity A could have been drawn from 10 to 40 and event 20 may be eliminated completely.

12

1. Drawing the PERT diagram.

2. Identifying the critical path.

Four paths:

10-20-30-50-60-70-80 22

10-20-30-40-60-70-80 19

10-30-50-60-70-80 19

10-30-40-60-70-80 16

It is essential that the systems analyst carefully monitor the activities on the critical path so as to keep the entire project on time.

Example:

13

PERT Diagram Advantages

Critical Path: The shortest time in which a project can be completed.

Slack (鬆弛的 ) time: The amount of time that an activity can be delayed with out delaying the project.

Advantages:• Easy identification of the order of precedence• Easy identification of the critical path and thus

critical activities• Easy determination of slack time, the leeway (多餘 ) to fall behind on noncritical paths

14

Here is key differences between Gantt Chart and PERT diagram.

• Gantt shows the duration of tasks and PERT shows the sequence dependencies between tasks.

• Gantt shows the time overlap of tasks. PERT does not show time overlap but does show which task could be done in parallel.

• Some forms of Gantt charts can show slack time available within an earliest start and latest finish duration. PERT shows this by data within activity rectangles.

PERT Diagram

Gantt Chart

15

Team Management

• Teams often have two leaders:– One who leads members to accomplish tasks.– One concerned with social relationships.

• The systems analyst must manage:– Team members.– Their activities.– Their time and resources.

16

Class Work 1

A system analysis consulting firm is working on a systems design project with the planning shown in the table.

Draw a Gantt Chart to help the firm organize its design project.

17

The Gantt Chart :

18

Class Work 2Tasks Preceding

EventExpected Duration

A: Write Objectives -- 1

B: Determine who to

interview

A 1

C: Write Questions B 2

D: Prepare Interviewee B 1

E: Interview Senior

Management

C, D 3

F: Interview Operations

Management

C, D 4

G: Record and Analyze

Observations

C, D 2

H: Summarize

Management Interview

E 1

I: Summarize

Operations Interviews

F 2

A project has been defined to contain the left list of activities along with their required times for completion.1. Draw a PERT diagram

for the activities.

2. List all paths and calculate and identify the critical path.

3. What would happen if activity D was revised to take 3 weeks instead of 1 weeks?

19

All paths: Days:

10 – 20 – 30 – 40 – 70 – 80 10

10 – 20 – 30 – 40 – 80 6

10 – 20 – 30 – 40 – 60 – 80 8

10 – 20 – 30 – 50 – 40 – 70 – 80 9

10 – 20 – 30 – 50 – 40 – 80 5

10 – 20 – 30 – 50 – 40 – 60 – 80 7

If activity G was revised to take 4

weeks instead of 2 weeks?

Answer : Nothing could happen.

20

Review Question

• What are the advantages of Gantt chart and PERT diagram?

• What is the different between Gantt chart and PERT diagram?

• Define the terms critical path, Slack time, Optimistic time, Pessimistic time and Realistic time.