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Project Management
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Project Management (Developing A Project Plan)
Introduction
• The project network is the tool used for planning, scheduling and monitoring project progress. The network is developed from the information collected for the WBS and is a graphic flow chart of the project job plan.
• The network depicts the project activities that must be completed, the logical sequences, the interdependencies of the activities to be completed, and in most cases the time for the activities to start and finish along with the longest path(s) through the network - critical path.
• The network is the framework for the project information system that will be used by the project managers to make decisions concerning project time, cost and performance.
• Project networks are developed from the WBS. The project network is a visual flow diagram of the sequence, interrelationships, and dependencies of all the activities that must be accomplished to complete the project.
• An activity is an element in the project that consumes time – for example work or waiting.
• Work packages from the WBS are used to build the activities found in project network.
From Work Package to Network
• Networks provide the project schedule by identifying dependencies, sequencing and timing of activities, which WBS is not designed to do.
• Primary inputs for developing a project a project network plan are work packages. Remember, a work package is defined independently of other work packages, has definite start and finish points, requires specific resources, includes technical specifications, and has cost estimates for the package. However, dependency, sequencing and timing of each of these factors are not included in the work package.
From Work Package to Network
From Work Package to Network
Circuit BoardLowestElement
Design Control A/C
Production Control A/C
Test Control A/C
Software Control A/C
Design WP D-1-1 SpecificationsWP D-1-2 Documentation)
ProductionWP P-10-1 Prototype 1WP P-10-2 Final Prototype 2
TestWP T-13-1 Test
Software WP S-22-1 Software PreliminaryWP S-22-2 Software Final Version
A
D-1-1D-1-2
B
P-10-1
C
S-22-1
D
P-10-2
F
S-22-2
K
T-13-1
A – Specifications and Documentations B – Prototype 1 C – Software Preliminary D – Final Prototype 2 F – Software Final Version K – Test
• Activity – An element of the project that requires time. It may or may not require resources. Typically, an activity consume resources – either while people work or while people wait.
• Merge Activity – An activity that has more than one activity immediately preceding it.
• Burst Activity – An activity that has more than one activity immediately following it.
• Parallel Activities – Activities that can take place at the same time.
• Path – A sequence of connected, dependent activities
• Critical Path – Longest path through the network. It has no slack or float.
• Event – A point in time when an activity is started or completed. It does not consume time.
Constructing a Project Network
Terminologies
• Activity on Node (AON) or Precedence Diagram Method
• Node to depict an activity
• Activity on Arrow (AOA) or Arrow Diagramming Method
• Arrow to depict an activity
Two Approaches
• Both methods use two building blocks – the arrow and the node.
Constructing a Project Network
Basic Rules to Follow in Developing Project Networks
• Network flow typically from left to right. • An activity cannot begin until all preceding connected activities have been completed.
• Arrows on networks indicate precedence and flow. Arrows can
cross over each other.
• Each activity should have a unique identifier number.
• An activity identification number must be larger than that of any activities that precedes it.
• Looping and conditional statements are not allowed.
• Experience suggests that when there are multiple starts, a common start node can be used to indicate a clear project beginning on the network.
• Similarly, a single project end node can be used to indicate a clear ending.
Constructing a Project Network
How to draw a network diagram
• Draw basic diagram with dependencies
• Add effort
• Forward Pass
• Backward Pass
• Calculate slack / identify critical path.
Constructing a Project Network
Activity-on-Node (AON)
AON Fundamentals
• Also called Precedence Diagram Method (PDM).
• Activity is represented by a node.
• Dependencies among activities are depicted by arrows.
• Length and slope of arrows are arbitrary and set for convenience of drawing the network.
AON Fundamentals
A is preceded by nothing. B is preceded by A.C is preceded by B.
A B C
A
B
C
A is called Burst ActivityB and C are preceded by A. B and C can start at the same time if you wish.
A
B
C
C is called Merge ActivityA and B can begin at the same time. They need to occur simultaneously. A and B must be completed before C can begin.
A
B
C is preceded by A and BD is preceded by A and B
C
D
Activity-on-Node (AON)
AON Fundamentals
• Three basic relationships that must be established for activities included in a project network. The relationships can be found by answering the following three questions:
• Which activities must be completed immediately before this activity. These activities are called predecessor activities.
• Which activities must immediately follows this activity. These activities are called successor activities.
• Which activities can occur while this activity is taking place. These activities are called parallel or concurrent activities.
Activity-on-Node (AON)
Activity-on-Node (AON) Fundamentals
• Drawing the project network places the activities in the right sequence for computing start and finish times of the activities. Activity time estimates are taken from the task times in the work packages and added to the network.
• Performing a few simple computations allow the project manager to complete a process known as the forward and backward pass.
Activity-on-Node (AON)
AON Fundamentals
• Forward Pass
• How soon can the activity start (Earliest Start)?• How soon can the activity finish (Earliest Finish)?• How soon can the project be finished (Expected Time)?
• Backward Pass
• How late can the activity start (Late Start)?• How late can the activity finish (Late Finish)?• Which activities represent the Critical Path?• How long can the activity be delayed (Slack or Float)?
Activity-on-Node (AON)
AON Fundamentals
• Forward Pass requires that you remember just three things when computing early activity times.
• Rule FP1: Add activity times along each path in the network. (ES + Dur = EF)
• Rule FP2: Carry the early finish (EF) to the next activity where it becomes its early start (ES), unless
• Rule FP3: The next succeeding activity is a merge activity, in which case, you select the largest early finish (EF) of all its immediate predecessor activities.
Activity-on-Node (AON)
AON Fundamentals
• Backward Pass requires that you remember just three things when computing late activity times.
• Rule BP1: Subtract activity times along each path starting with the project end activity. (LF – Dur = LS)
• Rule BP2: Carry the late start (LS) to the preceding activity where it becomes its late finish (ES), unless
• Rule BP3: The next preceding activity is a burst activity, in which case, you select the smallest late start (LS) of all its immediate successor activities to establish late finish (LF).
Activity-on-Node (AON)
AON Fundamentals
• Determining Slack / Float
• When the forward and backward passes have been computed, it is possible to determine which activities can be delayed by computing slack or float.
• Total slack tells us the amount of time an activity can be delayed and yet not delay the project. (Also called Project Slack).
• Critical path has a slack of zero (or minimum).
• Slack or Float (SL) = LF – EF = LS – ES
Activity-on-Node (AON)
AON Fundamentals
• Determining Free Slack / Float
• An activity with free slack is unique because the activity can be delayed without delaying the ES of activities following it. (Also called Task Slack)
• Defined as the difference between the EF of and activity and the ES of the successor activity.
• It can never be negative.
Activity-on-Node (AON)
Activity-on-Node (AON)
AON Fundamentals
• When the critical path is known, it is possible to tightly manage the resources of activities on the critical path so no mistakes are made that will result in delays.
Activity-on-Node (AON)
AON Example
• Project represents a new business center that is to be developed and the work and services the county engineering design department must provide as it coordinates with other groups – such as the business center owners and contractors.
Activity
ABCDEFGH
Description
Application approval Construction plans Traffic study Service availability check Staff report Commission approval Wait for construction Occupancy
Predecessor
None AAAB, CB, C, DFE, G
Time (Days)
5 15 10 5 15 10170 35
Koll Business CenterCounty Engineers Design Department
Activity-on-Node (AON)
ES EFID
LS LFDur
SL Description
A
5
Applicationapproval.
C
10
Traffic study.
F
10
Commissionapproval.
G
170
Wait for construction.
H
35
Occupancy.
D
5
Service check.
B
15
Constructionplans.
E
15
Staff report.
Develop a Network
Legend
AON Example
Activity-on-Node (AON)
ES EFID
LS LFDur
SL Description
Forward Pass
A
5
Applicationapproval.
C
10
Traffic study.
F
10
Commissionapproval.
G
170
Wait for construction.
H
35
Occupancy.
D
5
Service check.
B
15
Constructionplans.
E
15
Staff report.
0 5
Legend
Rule FP1
5
5
5
Rule FP2
20
15
10
20 30
Rule FP3
30 200
Rule FP3
35
200 235
Time to complete the project = 235 days
20
AON Example
Activity-on-Node (AON)
Rule FP2
Rule FP2
Rule FP2 Rule FP3
ES EFID
LS LFDur
SL Description
Backward Pass
A
5
Applicationapproval.
C
10
Traffic study.
F
10
Commissionapproval.
G
170
Wait for construction.
H
35
Occupancy.
D
5
Service check.
B
15
Constructionplans.
E
15
Staff report.
0 5
Legend
Rule BP1
5
5
5
20
15
10
20 30
Rule FP3
30 200
35
200 235
Time to complete the project = 235 days
235200
200
200
Rule BP2
Rule BP2
30
185
3020
20
20
Rule BP3
20
20
5
10
15
50
AON Example
Activity-on-Node (AON)
Rule BP1
Rule BP3
Rule BP2
Rule BP3
ES EFID
LS LFDur
SL Description
Backward Pass
A
5
Applicationapproval.
C
10
Traffic study.
F
10
Commissionapproval.
G
170
Wait for construction.
H
35
Occupancy.
D
5
Service check.
B
15
Constructionplans.
E
15
Staff report.
0 5
Legend
Rule BP1
5
5
5
20
15
10
20 30
Rule FP3
30 200
35
200 235
Time to complete the project = 235 daysCritical Path = A B F G H
235200
200
200
Rule BP2
Rule BP2
30
185
3020
20
20
Rule BP3
20
20
5
10
15
50
0
0
5
10
0 0 0
165
AON Example
Activity-on-Node (AON)
ES EFID
LS LFDur
SL Description
A
2 D
F
2
E
1
C
5
Legend
Another Example: Given the network diagram, draw bar chart.
Activity-on-Node (AON)
B
4
3 G
4
H
2
A
B
C
D
E
F
G
H
ES EFID
LS LFDur
SL Description
A
2 D
F
2
E
1
C
5
Legend
Another Example: Given the network diagram, draw bar chart.
Activity-on-Node (AON)
B
4
3G
4
H
2
A
B
C
D
E
F
G
H
0 2
0 4
2
4
4
7
7
5
7
7
9
11
11 13
13
0 1 2 3 4 5 6 7 8 9 10 11 12 13
1311
11
119
7
76
74
94
4
4
2
0
2
0
2
0
2
2
0
0
Activity-on-Arrow (AOA)
AOA Fundamentals
• Also called Arrow Diagramming Method (ADM).
• Activity is represented by a arrow.
• Length and slope of arrows are arbitrary and set for convenience of drawing the network.
• The node, usually represented by a small circle, represent an event. Events represent point in time but do not consume time.
• Each activity on the network has a start and end event node.
Activity-on-Arrow (AOA)
AOA Fundamentals
10 11 12X Y Y is preceded by X.
10 is start event for X. 11 is the end event for X and start event for Y.12 is the end event for Y.
5
10
15
20 25
R
S
T
U
U is preceded by R, S and T. R, S and T can occur concurrently if you wish. Event 20 is the merge event.
50 54M
75
79
N
O
N and O are preceded by M. When M is complete, N and O can start concurrently if you wish. Event 54 is the burst event.
Activity-on-Arrow (AOA)
AOA Fundamentals
21
19
23
E and F must precede G and H. E and F can occur together if you wish. G and H can occur together if you wish. Event 23 is both a merge event and a burst event.
24
28
E
F
G
H
62 64 66A B
76 77 78C D
A must precede B.C must precede D.Path A B is independent of path C D.
AOA Example
• Project represents a new business center that is to be developed and the work and services the county engineering design department must provide as it coordinates with other groups – such as the business center owners and contractors.
Activity
ABCDEFGH
Description
Application approval Construction plans Traffic study Service availability check Staff report Commission approval Wait for construction Occupancy
Predecessor
None AAAB, CB, C, DFE, G
Time (Days)
5 15 10 5 15 10170 35
Koll Business CenterCounty Engineers Design Department
Activity-on-Arrow (AOA)
AOA Example
Activity-on-Arrow (AOA)
1A, 5
2
3
4
5
B, 15
C, 10
D, 5
6E, 15
7F, 10
8G, 170
9H, 35
X
Y Z
Activity
A - Application approval B - Construction plans C - Traffic study D - Service availability check E - Staff report F - Commission approval G - Wait for construction H - Occupancy
Legend
ES EF
LS LF
SL
Develop a NetworkDur
AOA Example
Activity-on-Arrow (AOA)
1A
2
3
4
5
6
7 8 9
B
C
D
E
F G, 170 H, 35
Activity
A - Application approval B - Construction plans C - Traffic study D - Service availability check E - Staff report F - Commission approval G - Wait for construction H - Occupancy
Forward Pass
Legend
ES EF
LS LF
SL Dur
0 5
5
5 20
15
X
Y Z
5 10
5
5 15
10
20 35
15
20 30
10
30 200
170
200 235
35
AOA Example
Activity-on-Arrow (AOA)
1A
2
3
4
5
6
7 8 9
B
C
D
E
F G, 170 H, 35
Activity
A - Application approval B - Construction plans C - Traffic study D - Service availability check E - Staff report F - Commission approval G - Wait for construction H - Occupancy
Backward Pass
Legend
ES EF
LS LF
SL Dur
0 5
5
5 20
15
X
Y Z
5 10
5
5 15
10
20 35
15
20 30
10
30 200
170
200 235
35
200 235200
200
30
185
3020
20
20
20
10
5
15
50
AOA Example
Activity-on-Arrow (AOA)
1A
2
3
4
5
6
7 8 9
B
C
D
E
F G H
Activity
A - Application approval B - Construction plans C - Traffic study D - Service availability check E - Staff report F - Commission approval G - Wait for construction H - Occupancy
Backward Pass
Legend
ES EF
LS LF
SL Dur
0 5
5
5 20
15
X
Y Z
5 10
5
5 15
10
20 35
15
20 30
10
30 200
170
200 235
35
200 235200
200
30
185
3020
20
20
20
10
5
15
50
000
165
5
0
10
0
Time to complete the project = 235 daysCritical Path = A B X Y F G H
Another Example: Given the network diagram, draw bar chart.
Activity-on-Arrow (AOA)
A
B
C
D
E
F
G
H
1
2
3
A, 2
C, 1
Legend
ES EF
LS LF
SL Dur
5
D, 3
E, 4
6
F, 3
G, 2
0 1 2 3 4 5 6 7 8 9 10 11 12 13
B, 3
4
Another Example: Given the network diagram, draw bar chart.
Activity-on-Arrow (AOA)
A
B
C
D
E
F
G
1
2
3
A, 2
C, 1
Legend
ES EF
LS LF
SL Dur
5
D, 3
E, 4
6
F, 3
G, 2
0 1 2 3 4 5 6 7 8 9
B, 3
4
0 2
0 3
0 1
2 5
3 7
7 9
1 4
2
3
1
3
4
2
3
9
96
7
65
7
7
3
4
30
42
2
5
0
2
0
5
0
Comparison or AON and AOA
AON Method AOA Method
• No dummy activities are used.
• Events are not used.
• Easy to draw if dependencies are not intense.
• Activity emphasis is easily understood by first level managers.
• CPM approach uses deterministic times to construct networks.
• Path tracing is simplified by activity / event numbering scheme.
• AOA is easier to draw if dependencies are intense.
• Key events or milestones can easily be triggered.
Advantages
• Path tracing by activity number is difficult.
• Network drawing and understanding are difficult when dependencies are numerous.
• Use of dummy activities increases data requirements. • Emphasis on events can detract from activities. Activity delays cause events and projects to be delayed.
Disadvantages
Extended Network Techniques
• The method for showing relationships among activities in the previous examples is called finish-to-start relationship because it assumes that all immediate preceding connected activities must be completed before the next activity can begin.
• In order to come close to the realities of projects, some useful extensions have been added, such as, laddering, use of lags and leads, and different form of relationships, other than just finish-to-start.
Extended Network Techniques
Laddering
Trench (1/3) Trench (1/3) Trench (1/3)
Lay Pipe (1/3) Lay Pipe (1/3) Lay Pipe (1/3)
Refill (1/3) Refill (1/3) Refill (1/3)
Extended Network Techniques
Use of Lags
• A lag is the minimum amount of time a dependent activity must be delayed to begin or end .
• The use of lags has been developed to offer greater flexibility in network construction.
• Use of lags with Finish-to-Start, Start-to- Start, Finish-to-Finish and Start-to-Finish relationships is discussed next.
Extended Network Techniques
Lag with Start-to-Finish Relationship
• There are situations in which the next activity must be delayed even when the preceding activity is complete.
• Example: removing concrete forms cannot begin until the poured cement has cured.
• Also, used when ordering materials. For example, it takes one day to place the order but 19 days to receive the goods. This ensures that activity cost is tied to placing the order only
rather than charging the activity for 20 days of work.
Activity A Activity BLag 2
Extended Network Techniques
Lag with Start-to-Start Relationship
• This situation typically depicts a situation in which you can perform a portion of one activity and begin a following activity without completing the first.
• Example: Laying of pipeline.
• Reduces the network detail and project delays by using lag relationships.
• It is possible to find compression activities by changing finish-to-start relations to start-to-start relations with lags.
Trench
Lay PipeLag 3
RefillLag 3
Extended Network Techniques
Lag with Finish-to-Finish Relationship
• The finish of one activity depends on the finish of another activity.
• Example: testing cannot be completing any earlier than four days after the prototype is complete. Note that this is not a finish-to-start relationship as testing of subcomponents can be done before the prototype is completed, but four days of system testing is must after a prototype is finished.
Prototype
Testing
Lag 4
Extended Network Techniques
Lag with Start-to-Finish Relationship
• The finish of one activity depends on the start of another activity.
• Rarely used.
• Example: System documentation can not end until three days after testing has started. Here all the relevant information to complete the system documentation is produced the first three days of testing.
Testing
Doc.
Lag 3
Extended Network Techniques