Unit 10 – Network Logic and Scheduling

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

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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

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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"

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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!

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Schedule Types

Networking Activity-on-arrow (AOA)

Precedence diagram method (PDM)

Gantt chart Milestone chart

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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

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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

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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

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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

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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

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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

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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

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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

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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)

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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

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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

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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)

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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

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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

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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

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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

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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

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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

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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)

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Critical Path

Longest of all paths through the project

Shortest time to complete the project

Path with least float/slack time

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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

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Benefits of Critical Path Method

Shows explicit relationships

Coordinates "big picture"

Lays out flow of work

Encourages careful task analysis

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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

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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?

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Network Analysis (continued)

Analyze against target costs and schedule

Resource usage Overallocated ?

Availability ?

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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

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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

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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

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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

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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

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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

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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

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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

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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

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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

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Sample Gantt Chart

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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

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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

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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

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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

Unit 10 – Network Logic and Scheduling

Documents

Transcript of Unit 10 – Network Logic and Scheduling