Software Project Management
Task Sequencing
Activity Sequencing Concepts
PERT charts
Critical Path Analysis
Project Time Management Processes
Project time management involves the processes required
to ensure timely completion of a project. Processes include:
 Activity definition (your WBS)
 Activity sequencing (this topic)
 Activity duration estimating (next week)
Time
Quality Expectations Cost
Activity Definition
• This comes from your WBS
Scope
 Recall it encompasses the total scope of the project
 It is organized by a perspective, or organizing principle
• What it doesn’t do: Help you plan temporally
 You need to know X needs to be done before Y because X may
produce a deliverable (or knowledge) required for Y
 You may need to ensure you can provide all of the resources
(people, technology, etc.) at a given time to ensure success
Activity Sequencing
Involves developing a more detailed WBS and supporting
explanations to understand all the work to be done
 An outgrowth of your WBS’ work packages
 Initial dependencies should arise
• What needs to be done before to make data available (flow)
• What tasks are a “part of” other tasks (decomposition)
• This is the resulting sequencing of activities to achieve goals
Review activities and determine dependencies
 Mandatory: inherent in the nature of the work; hard logic
• Example: Coding must happen before testing
 Discretionary: defined by the team; soft logic applied within a process
• Example: Order in which components are implemented
 External: involve relationships between project & non-project activities
• Example: 3rd party / open source software release
 Resource: Multiple projects depend on same resource
• Example: You have only 1 Oracle-certified DBA but 2 projects
Activity Sequencing
Tools for Activity Sequencing
 Task networks, PERT charts, Critical Path Analysis
Task networks
 A graphical representation of tasks
 Visualizes tasks, flows, and relationships
 Two formats:
• Activity-on-Arrow (AOA)
– Nodes represent Events, Lines represent Tasks
• Activity-on-Node (AON)
– Nodes represent Tasks, Lines dependencies between Tasks
Write
Unit Test
AON:
START
Code
Module
Perform
Code Review
Fix
Defects
Check-in
Code
AOA Example
*Taken from Scach 4th ed. P. 289
Activity Sequencing
Temporal Dependencies between Tasks
• Finish-to-Start (FS)
 B cannot start till A finishes
 A: Construct fence; B: Paint Fence
• Start-to-Start (SS)
 B cannot start till A starts
 A: Pour foundation; B: Level concrete
• Finish-to-Finish (FF)
 B cannot finish till A finishes
 A: Add wiring; B: Inspect electrical
• Start-to-Finish (SF)
 B cannot finish till A starts (rare)
Critical Path Method (CPM)
CPM is a project network analysis technique used to predict
total project duration
 A critical path is the series of activities that determines the earliest
time by which the project can be completed
 The critical path is the longest path through the network diagram
and has the least amount of slack or float
 Typically used in conjunction with PERT charts (or also with ActivityTask Analysis, Task Networks, etc.)
Finding the Critical Path
 First develop a good project network diagram
 Add the durations for all activities on each path through the project
network diagram
 The longest path is the critical path
Course Technology, 1999
Determining the Critical Path
Consider the following project network (AOA)
diagram. Assume all times are in days.
C=2
start
1
A=2
2
B=5
4
E=1
3
6
D=7
5
finish
F=2
a. How many paths are on this network diagram?
b. How long is each path?
c. Which is the critical path?
d. What is the shortest amount of time needed to
complete this project?
Course Technology, 1999
Determining the Critical Path
Example (AOA):
Course Technology, 1999
More on the Critical Path
Misconceptions:
 The critical path is not the one with all the critical
activities; it only accounts for time
 There can be more than one critical path if the lengths
of two or more paths are the same
 The critical path can change as the project progresses
If one of more activities on the critical path takes
longer than planned, the whole project schedule
will slip unless corrective action is taken
 We will discuss what “corrective actions” are possible
with scheduling next week.
Course Technology, 1999
PERT Charts
Program Evaluation and Review Technique
 Network analysis technique used to estimate project duration if there is a high
degree of uncertainty about individual activity duration estimates
 PERT uses probabilistic time estimates based on using optimistic, most likely,
and pessimistic estimates of activity durations
Requirements
Definition (Analysis)
1
8/1/95
9/11/95
EXAMPLE:
Prepare for Analysis
2
8/1/95
8/7/95
Define System
Requirements (Business)
3
ITDE(0.3),ITI
8/8/95
8/14/95
Analyze the Current
System
4
8/8/95
8/14/95
Reaccess Application
Architecture
5
ITDBA(0.3)
8/8/95
8/14/95
Develop and Evaluate
Alternative Solutions
6
8/15/95
8/21/95
Outline Transaction,
Security and Training
7
ITDBA(0.3)
8/15/95
8/21/95
Plan the Next Stage
8
8/22/95
8/28/95
Prepare Material for
Business Management
9
8/29/95
9/4/95
Conduct the Business
Management Review
10
9/5/95
9/11/95
RD Approved by IS Dir,
DMA Dir, Cust Sponsor
11
9/11/95
9/11/95
Approval to Proceed to
Next Stage
12
Course Technology, 1999
9/11/95
9/11/95