unit 10 – network logic and scheduling
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October 2003 | Project Management | Wilhelm F. Neuhäuser © IBM Corporation 2003
Unit 10 – Network Logic and Scheduling
Project Management
Unit 10 | Network Logic and Scheduling © IBM Corporation 20032
Agenda
Unit 10: Network Logic and Scheduling Objectives A practical approach to project scheduling Schedule types Project scheduling Network analysis Leveling Rolling-wave planning concept Gantt chart Milestone chart Key Messages - Unit 10
Project Management
Unit 10 | Network Logic and Scheduling © IBM Corporation 20033
Objectives
At the end of this module, you will be able to - Define networks and schedules
Identify various types of logic networks and approaches, and weigh their relative merits for specific development projects
Use logic networks and scheduling approaches appropriate to their particular projects
Integrate a WBS into a logic network and determine a schedule for that network
Incorporate risk into scheduling considerations
Project Management
Unit 10 | Network Logic and Scheduling © IBM Corporation 20034
A Practical Approach to Project Scheduling
Working rules Time is usually the critical factor
Scheduling and risk management functions are the foundation for project control
You should be able to predict probable delays, initiate steps, and always include in a report -
Impact of the delay
Steps to be taken to avoid or reduce delay
"Key events" (to be defined) and milestones are to be recognized as deadlines
Anyone who is not fulfilling his or her timely obligation should be immediately notified
The project manager is not a "schedule mechanic"
Project Management
Unit 10 | Network Logic and Scheduling © IBM Corporation 20035
A Practical Approach to Project Scheduling (continued)
The tools Use a project management tool (like MS Project) for
scheduling based on the common WBS
Have internal and external suppliers, project team members, and business partners participate in the scheduling (according to the main project schedule), identify who is allocated to a task, and report on agreed-upon key events
Make obligations such as submitting data, approving deliverables, and meeting other obligations, an integrated part of the project schedule
Emphasize key events more than activities
Strictly define events regarding contents so that cause of a delay can be concisely and quickly identified
Project management is management of interfaces!
Project Management
Unit 10 | Network Logic and Scheduling © IBM Corporation 20036
Schedule Types
Networking Activity-on-arrow (AOA)
Precedence diagram method (PDM)
Gantt chart Milestone chart
Project Management
Unit 10 | Network Logic and Scheduling © IBM Corporation 20037
Project Scheduling
KEY:
CompleteIn progress
Start Review Approve
Start Review Approve
Start Complete
Milestonechart
Tasks
1. Design
2. Build
3. Test
Networkchart
Ganttchart
Tasks
Task 1
Task 2
Task 3
1 2 3
4 5 7
6 8
Project Management
Unit 10 | Network Logic and Scheduling © IBM Corporation 20038
Network Scheduling
Schedule flows from WBS work packages' planned or actual duration
Schedules may be driven by amount of resources required
Schedule is a major element of project baseline (along with expense and technical considerations)
Shows time to finish and activity interdependencies Provides greatest amount of information - useful for
detailed analysis Two types
Activity-on-arrow
Precedence diagram method
Project Management
Unit 10 | Network Logic and Scheduling © IBM Corporation 20039
Essential Scheduling Data (Example)
Activity ImmediatelyPreceding Activity
Expected Completion Time (days)
a Initiate project - 5b Assign PM a 2c Establish constraints a 6d Form project development team b 12e Develop project schedules d 10f Prepare expense estimates d 9g Conduct process training d 5h Design integrated project file (IPF) b 9i Assign resources c,e 1j Prepare business case g 2k Write integrated project plan (IPP) f,i,j 3l Finalize IPP k 9
m Conduct IPF training h,g 7n Reproduce documents m 8
Activities and Times
Project Management
Unit 10 | Network Logic and Scheduling © IBM Corporation 200310
Networks can be used for CPM and Slack Analysis
Activity-on-arrow
Start5a
Initiate project
2b
Assign PM
12d
Form projectdevelopment team
9f
Prepare expenseestimate
3k
Write IPP
9l
FinalizeIPP
Concept check point
6c
Establish constraints
10e
Develop project schedule
1 iAssign resources
9h
Design IPF
5 gConduct processtraining
7m
ConductIPF training
8 nReproducedocuments
2 jPreparebusiness case
Project Management
Unit 10 | Network Logic and Scheduling © IBM Corporation 200311
Precedence Diagram Method
Start(a)
Initiateproject
(c) Establish
constraints
(e) Developproject
schedule
(b) Assign
PM
(d) FormPDT
(h) Design
IPF
(g) Conductprocesstraining
(f) Prepareexpenseestimates
(i) Assign
resources
(j) Preparebusiness
case
(m) Conduct
IPFtraining
(k) WriteIPP
(l) Finalize
IPP
Finishcheck point
(n) Reproducedocuments
Project Management
Unit 10 | Network Logic and Scheduling © IBM Corporation 200312
Basic Scheduling Terminology
Activity: A task (work package) performed over a period of time; a specific piece of defined work from WBS
Milestone: Zero time duration activity Relationships: Dependencies that exist between
activities Free float: The amount of time an activity can be
delayed without delaying the early start of any immediately following activities
Project Management
Unit 10 | Network Logic and Scheduling © IBM Corporation 200313
Basic Scheduling Terminology (continued)
Total float: The amount of time that an activity may be delayed from its early start without delaying the project finish date
Critical path: Longest time period from start to completion of a project; also the shortest total length of the project
Lag: Imposed delay between the start or finish of one activity and the start or finish of another
Project Management
Unit 10 | Network Logic and Scheduling © IBM Corporation 200314
Basic Scheduling
Activity nameDuration
ES
LS
EF
LF
Early Start Early Finish
Late FinishLate Start
Earliest an activitycan start, based on
project logic
Earliest an activitycan finish, based on
Early Start
Latest an activitycan start, withoutdelaying project
completion, basedon Late Finish
Latest an activitycan finish, withoutdelaying project
completion, based onproject end date
Project Management
Unit 10 | Network Logic and Scheduling © IBM Corporation 200315
Types of Relationships
Finish Start
Activity1
Activity2
Activity 1 must be totally finished before Activity 2 can start: traditional
Example: Define requirements (Activity 1), perform DCUT - design, code, unit test (Activity 2)
Project Management
Unit 10 | Network Logic and Scheduling © IBM Corporation 200316
Types of Relationships (continued)
Finish Finish
Activity1
Activity2
Activity 2 cannot finish until Activity 1 finishes Example: Activity 2 (reviewing the high-level
design) cannot be finished until Activity 1 (writing the high-level design) is finished
Project Management
Unit 10 | Network Logic and Scheduling © IBM Corporation 200317
Types of Relationships (continued)
Activity 2 cannot start until Activity 1 begins; a lag of n time units can be defined
Example: Reviewing the specifications (Activity 2) can begin after writing the specifications (Activity 1) begins
Start Start
Activity1
Activity2
Project Management
Unit 10 | Network Logic and Scheduling © IBM Corporation 200318
Hard Coding Relationship Constraints
Start no earlier than (SNET) Start no later than (SNLT) Finish no earlier than (FNET) Finish no later than (FNLT) Must start on (MSO) Must finish on (MFO)
Project Management
Unit 10 | Network Logic and Scheduling © IBM Corporation 200319
Using the Hard Constraints
Cautions They will override the normal critical-path
calculations They remove naturally occurring float in your
schedule
Useful for - Creating milestone charts Positioning activities to eliminate excessive float
Project Management
Unit 10 | Network Logic and Scheduling © IBM Corporation 200320
Network Calculations
Forward pass through the network (beginning at
project start) determines Early Start and Early
Finish for each activity
Backward pass through the network (beginning at
project finish) determines Late Finish and Late
Start for each activity
Project Management
Unit 10 | Network Logic and Scheduling © IBM Corporation 200321
Forward Pass
Established: Project Start date
Project Start date is the Early Start date for first network activity
Work from left to right, top to bottom of the network
When an activity has multiple predecessors (P), select highest Early Finish date as Early Start date of successor (S)
Calculations ESP + Duration = EFP
EFP + Lag = ESS
Project Management
Unit 10 | Network Logic and Scheduling © IBM Corporation 200322
Forward Pass (continued)
Full precedence diagram
Start Finish
Duration=7Task A
Duration=6Task C
Duration=3Task G
Duration=3Task B
Duration=3Task D
Duration=3Task E
Duration=2Task F
Duration=2Task H
1 8 8 14 14 171
1 4 4 7 7 10
1917
4 6
ES ES ES
ES ES ES
ES
EF EF EF
EF EF EF
EF
LF
LF
LF LF
LF LF
LF
LS LS LS
LS
LS
LS LS
ES EF
LFLS
Project Management
Unit 10 | Network Logic and Scheduling © IBM Corporation 200323
Backward Pass
Established: Project Finish date (from last activity in Forward Pass)
Project Finish date is the Late Finish date for last network activity in the Backward Pass
Work from left to right, top to bottom of network
When a predecessors (P) has multiple successors (S), select the lowest Late Start date as the Late Finish of the predecessor
Calculations LFS - Duration = LSS
LSS - Lag = LFP
Project Management
Unit 10 | Network Logic and Scheduling © IBM Corporation 200324
Backward Pass (continued)
Full precedence diagram
Start Finish
Duration=7Task A
Duration=6Task C
Duration=3Task G
Duration=3Task B
Duration=3Task D
Duration=3Task E
Duration=2Task F
Duration=2Task H
1 8 8 14 14 17
1 4 4 7 7 10
1917
4 6
ES ES ES
ES ES ES
ES
EF EF EF
EF EF EF
EF
LF
LF
LF LF
LF LF
LF
LS LS LS
LS
LS
LS LS
ES EF
LFLS
1 8 8 14 14 17
8
12 14
11 11 14 14 17
17 19
Project Management
Unit 10 | Network Logic and Scheduling © IBM Corporation 200325
Float/Slack
Float = Late Finish - Early Finish
or
Float = Late Start - Early Start
Float/Slack > 0 (time is available)
Float/Slack = 0 (path is critical)
Float/Slack < 0 (project is behind schedule/critically late)
Project Management
Unit 10 | Network Logic and Scheduling © IBM Corporation 200326
Critical Path
Longest of all paths through the project
Shortest time to complete the project
Path with least float/slack time
Project Management
Unit 10 | Network Logic and Scheduling © IBM Corporation 200327
Process for Computing Critical Path Network Schedule
Step 1 Establish a "begin" activityStep 2 Identify all activities that can begin immediately (that is, that have no
predecessors)Step 3 Identify what, as a result of the activities being started/completed, can now
start/endStep 4 Complete process until all predecessors and successors have been
identifiedStep 5 Make "end" the final activityStep 6 Calculate the forward pass; when multiple dates must be passed forward,
select the latest date Step 7 Establish the natural end date of the projectStep 8 Calculate the backward pass; when multiple dates must be passed
backward, select the earliest dateStep 9 Calculate floatStep 10 Identify the critical path and paths with low levels of floatStep 11 Restrict the project by adding any intermediate end date constraintsStep 12 Recalculate the backward passStep 13 Recalculate floatStep 14 Identify the critical path and paths with low levels of floatStep 15 Use networking techniques to eliminate any negative float
Project Management
Unit 10 | Network Logic and Scheduling © IBM Corporation 200328
Benefits of Critical Path Method
Shows explicit relationships
Coordinates "big picture"
Lays out flow of work
Encourages careful task analysis
Project Management
Unit 10 | Network Logic and Scheduling © IBM Corporation 200329
Exercise: Precedence Diagram Method
A I
G
H
F
E
D
C
B
12
14
13
14
8
19
16
8
12
SS+10
FS+6
1. Calculate the forward and backward passes2. Identify the critical path3. Calculate the float for each path
Project Management
Unit 10 | Network Logic and Scheduling © IBM Corporation 200330
Network Analysis
Is the critical path what I expected?
How much float is in the schedule? Do I need to do anything about it?
Should activities with large amounts of float be rescheduled?
Are there any near-critical paths?
What risks are on the critical path?
Danglers No predecessor?
No successor?
Project Management
Unit 10 | Network Logic and Scheduling © IBM Corporation 200331
Network Analysis (continued)
Analyze against target costs and schedule
Resource usage Overallocated ?
Availability ?
Project Management
Unit 10 | Network Logic and Scheduling © IBM Corporation 200332
Making Up Time in a Schedule During Planning
Change the relationships among tasks so that the critical path is shorter (fast tracking)
Do tasks in parallel, instead of sequentially
Contract out tasks that are being done in series because of lack of available personnel
Change approach to work, creating a different set of interrelated tasks with shorter critical path
Change a Finish-Start relationship to a Finish-Finish relationship
Change a date constraint so a task on the critical path can start or end sooner
Project Management
Unit 10 | Network Logic and Scheduling © IBM Corporation 200333
Leveling
Resource leveling
Schedule the project inn such a way as to use resources most effectively
Schedule the project to minimize idle time for resources
Avoid committing resources in such a way that exceeds resource capacity
Project Management
Unit 10 | Network Logic and Scheduling © IBM Corporation 200334
Leveling (continued)
Resource allocation leveling
Distribution of resources to the schedule
Resource constraints vs. time constraints
Priority rules for resource allocation
Examples of resource allocation
Use of analysis of resource histograms
Project Management
Unit 10 | Network Logic and Scheduling © IBM Corporation 200335
Resource Utilization 1
Tasks 1 2 3 4 5 6 7 8 9 Total
Initiate project 2 2
Assign PM 3 3
Establish constraints 2 2 4
Form project development team 4 4 8
Develop project schedules 2 2 4
Prepare expense estimates 2 2 4
Conduct process training 4 4
Design integrated project file (IPF) 3 3
Prepare business case 4 4
Write integrated project plan (IPP) 3 3
Finalize IPP 3 3 6
Conduct IPF training 3 3
Reproduce documents 4 4
Totals 2 5 9 4 8 8 10 3 3 52
Weeks
Project Management
Unit 10 | Network Logic and Scheduling © IBM Corporation 200336
Resource Histogram 1
1 2 3 4 5 6 7 8 9
Weeks
0
2
4
6
8
10
(max
= 8
)N
umbe
r of
Res
ourc
es
Project Management
Unit 10 | Network Logic and Scheduling © IBM Corporation 200337
Review Float
Late Start/Late Finish dates1 2 3 4 5 6 7 8 9
Float
Initiate project Assign PM Write IPP
Float Design IPF
FloatConduct
IPD training
Prepare business
case
FloatConduct
IPF training
Float Reproduce documents
Establish constraints
Form project dev. team Develop project schedule Finalize IPP
Prepare expense estimate
Project Management
Unit 10 | Network Logic and Scheduling © IBM Corporation 200338
Resource Utilization 2Weeks
Tasks 1 2 3 4 5 6 7 8 9 Total
Initiate project 2 2
Assign PM 3 3
Establish constraints 2 2 4
Form project development team 4 4 8
Develop project schedules 2 2 4
Prepare expense estimates 2 2 4
Conduct process training 4 4
Design integrated project file (IPF) 3 3
Prepare business case 4 4
Write integrated project plan (IPP) 3 3
Finalize IPP 3 3 6
Conduct IPF training 3 3
Reproduce documents 4 4
Totals 2 3 4 9 6 8 7 6 7 52
Project Management
Unit 10 | Network Logic and Scheduling © IBM Corporation 200339
Resource Histogram 2
1 2 3 4 5 6 7 8 9
Weeks
0
2
4
6
8
10
(max
= 8
)N
umbe
r of
Res
ourc
es
Project Management
Unit 10 | Network Logic and Scheduling © IBM Corporation 200340
Rolling-Wave Planning Concept
Detailed planning of entire project may not be practical or possible
Plan finite increments at outset based on project phases (work packages of early efforts, planning packages beyond)
Expand the detailed planning window as each project phase is completed; for longer project phases, plan in increments of 90 days
The planning window will vary based on size, length, complexity, and type of development project (for example, new, derivative, refresh)
Remember to include planning time in project plan
Project Management
Unit 10 | Network Logic and Scheduling © IBM Corporation 200341
Gantt Chart
Shows start, finish, and duration of various activities
Easiest schedule to make
Most common scheduling tool
Provides tremendous amounts of information - very useful for analysis
Most understandable for people lacking formal project management training
Software capabilities greatly enhance usefulness for analysis
Project Management
Unit 10 | Network Logic and Scheduling © IBM Corporation 200342
Sample Gantt Chart
Project Management
Unit 10 | Network Logic and Scheduling © IBM Corporation 200343
Milestone Chart
Reflects project status of key events over time
Activity
Concept Checkpoint
Plan Checkpoint
DCUT start
SVT start
Delivery to customer
January February March April May June
Project Management
Unit 10 | Network Logic and Scheduling © IBM Corporation 200344
Before Finalizing Schedule, Examine...
Roles: Is there a complete set of roles for each task? Actions: Add roles where needed
People: Who will fill these roles? Action: Assign people
Skills: Do the people assigned possess the needed skills? Action: Add or change people or re-estimate the duration to
allow time to improve skill levels
Availability: When will the people really be available? Action: Reschedule around nonavailable time
Action: Change utilization assumptions to adjust duration
Action: Add more people
Project Management
Unit 10 | Network Logic and Scheduling © IBM Corporation 200345
Key Messages
Time is usually a critical factor in development projects
A variety of tools can evaluate and map out schedules
Project managers must know how to evaluate their schedules and the potential for schedule improvement
Project Management
Unit 10 | Network Logic and Scheduling © IBM Corporation 200346
Exercise: Precedence Diagram Method
A I
G
H
F
E
D
C
B
12
14
13
14
8
19
16
8
12
SS+10
FS+6
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