SCHEDULINGGUIDE

FORPROGRAM

MANAGERS

October 2001

PUBLISHED BY THEDEFENSE SYSTEMS MANAGEMENT COLLEGE PRESS

FORT BELVOIR, VA 22060-5565

For sale by the U.S. Government Printing OfficeSuperintendent of Documents, Mail Stop: SSOP, Washington, DC 20302-9328

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FOREWORD

This guide provides an introduction to scheduling intended for use by governmentprogram managers and industry program of project managers and their respective staffs.It is the third version of a 1986 publication prepared by Mr. David D. Acker, Mr. J. StanleyBaumgartner, and Mr. Michael B. Patterson. A second version, published in 1994, wasprepared by Mr. William W. Bahnmaier and Mr. Paul T. McMahon.

This version addresses many of the topics contained in their earlier versions, especiallythose relating to the different types of scheduling techniques. The major differencebetween this and the previous versions is the treatment of scheduling as part of theacquisition process and the overall program management effort, particularly as it relatesto the planning and control functions of program management. Scheduling is discussedin the context of the development of integrated master plans and schedules, the riskmanagement process, and earned value management.

This guide is not intended as a detailed treatment of scheduling techniques. Instead, it ismore of a primer on the subject, addressing the importance of scheduling and theapplication of basic scheduling techniques. It is a compilation of information from varioussources, and hopefully will serve as a starting point for those who desire to delve deeperinto the various scheduling techniques.

The proliferation of microcomputers has greatly enhanced the capability of managers at alllevels to develop and analyze schedules. Chapter 9 provides an overview of the types ofautomated tools available and information on desirable features of scheduling softwareapplications.

This document reflects the efforts of many people. Mr. William W. Bahnmaier , Mr. PaulT. McMahon , Lt Col. David Bachman, USAF, and Mr. John Kelley of the DAU/DSMCfaculty provided invaluable guidance and advice. Mr. Gregory T. Caruth of the DAU/DSMC Press was very helpful in the composition of the guide. Frances M. Battle, provideddesktop publishing skills. Mr. Van Kinney, Ms. Joni Forman and Mr. Tom Parry of the OSDAcquisition, Resources and Analysis staff provided comments on the draft and overallsupport for the project. Special recognition also goes to the Institute for Defense Analysisteam of Mr. Lou Simpleman, Mr. Jim Lloyd, Mr. George Tolis, Ms. Patti Phillips, Ms. TinaHiggins, and Ms. Yolanda Prescott, who wrote, edited, and prepared the major portionsof the text.

Norman A. McDanielChairProgram Management and LeadershipDepartment

William W. BahnmaierEditorProgram Management and LeadershipDepartment

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CONTENTS

Chapter 1 INTRODUCTION ................................................................................................. 11.1 Overview ........................................................................................................................ 21.2 Purpose of This Guide .................................................................................................. 21.3 Guide Content ................................................................................................................ 21.4 Other Sources of Data ................................................................................................... 2

Chapter 2 PROGRAM MANAGEMENT AND THE ACQUISITION PROCESS .......... 32.1 Program Management Overview ................................................................................ 32.2 The Evolution of Program Management ................................................................... 42.3 The Acquisition Process and Scheduling .................................................................. 52.4 Risk Management and Scheduling ............................................................................. 6

Chapter 3 PROGRAM MANAGEMENT AND SCHEDULING ....................................... 73.1 Program Planning and Scheduling ............................................................................. 73.2 Work Breakdown Structure ......................................................................................... 8

3.2.1 Integrated Master Plans/Schedules .............................................................. 103.3 Program Controlling and Scheduling ........................................................................ 11

3.3.1 Earned Value Management ............................................................................ 113.4 Schedule Preparation .................................................................................................... 13

3.4.1 Activity Definition ........................................................................................... 133.4.2 Activity Sequencing ......................................................................................... 143.4.3 Activity Duration Estimating ......................................................................... 143.4.4 Schedule Development ................................................................................... 153.4.5 Schedule Control .............................................................................................. 15

3.5 Schedule Risk ................................................................................................................. 163.6 Summary ......................................................................................................................... 17

Chapter 4 SCHEDULE TYPES AND THEIR EVOLUTION ............................................. 194.1 Introduction .................................................................................................................... 194.2 Schedule Types .............................................................................................................. 19

4.2.1 Gantt and Milestone Charts ............................................................................ 194.2.2 Network Schedules .......................................................................................... 214.2.3 Production Schedules ...................................................................................... 23

4.3 Summary ......................................................................................................................... 24

Chapter 5 GANTT AND MILESTONE CHARTS ............................................................... 255.1 Description ..................................................................................................................... 255.2 Constructing Gantt and Milestone Charts ................................................................. 315.3 Gantt and Milestone Chart Advantages and Disadvantages .................................. 32

5.3.1 Advantages ....................................................................................................... 325.3.2 Disadvantages .................................................................................................. 32

5.4 How and When Gantt and Milestone Charts Are Employed ................................. 32

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5.5 Summary ......................................................................................................................... 33

Chapter 6 NETWORK SCHEDULING ................................................................................ 356.1 Description ..................................................................................................................... 35

6.1.1 PERT .................................................................................................................. 366.1.2 CPM .................................................................................................................... 376.1.3 PDM ................................................................................................................... 38

6.2 Network Scheduling Advantages and Disadvantages ............................................ 416.2.1 Advantages ....................................................................................................... 416.2.2 Disadvantages .................................................................................................. 41

6.3 How and When To Network Schedules Are Employed ......................................... 416.3.1 PERT Example .................................................................................................. 426.3.2 CPM Example ................................................................................................... 446.3.3 PDM Example ................................................................................................... 46

6.4 Network Scheduling When Resources Are Limited ................................................ 496.5 Summary ......................................................................................................................... 51

Chapter 7 PRODUCTION SCHEDULING .......................................................................... 537.1 Description ..................................................................................................................... 53

7.1.1 Objective Chart ................................................................................................. 547.1.2 Production Plan Chart ..................................................................................... 547.1.3 Program Status Chart ....................................................................................... 567.1.4 Line of Balance ................................................................................................. 56

7.2 How and When To Use the Line of Balance Techniques ........................................ 577.2.1 General ............................................................................................................... 577.2.2 Analysis ............................................................................................................. 57

7.3 Line of Balance Advantages and Disadvantages ...................................................... 587.3.1 Advantages ....................................................................................................... 587.3.2 Disadvantages .................................................................................................. 58

7.4 Summary ......................................................................................................................... 58

Chapter 8 TIME MANAGEMENT ....................................................................................... 598.1 Time Management and the Program .......................................................................... 59

8.1.1 Time Reserve .................................................................................................... 598.1.2 “Now” Schedule ................................................................................................ 598.1.3 Value of Time .................................................................................................... 60

8.2 Time Management and the Program Manager ......................................................... 628.3 Summary ......................................................................................................................... 63

Chapter 9 AUTOMATED SCHEDULING TOOLS ............................................................ 659.1 Automated Planning Aids ........................................................................................... 659.2 Functional Characteristics and Features .................................................................... 669.3 Evaluating Project Management Software Projects .................................................. 689.4 Finding Out More .......................................................................................................... 70

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APPENDIX A INTEGRATED MASTER SCHEDULE ..................................................... 71

APPENDIX B TIME ROBBERS ........................................................................................... 77

APPENDIX C GLOSSARY .................................................................................................. 79

APPENDIX D BIBLIOGRAPHY ......................................................................................... 83

FIGURES3-1 Generic Aircraft System WBS ....................................................................................... 93-2 IMP/IMS Sample ........................................................................................................... 104-1 Gantt Chart Example ..................................................................................................... 204-2 Milestone Chart Example ............................................................................................. 214-3 Network Schedule Example ........................................................................................ 225-1 Example Gantt Chart Symbols ..................................................................................... 255-2 Example Gantt Chart ..................................................................................................... 265-3 Example Milestone Chart Symbols ............................................................................. 275-4 Example Milestone Chart ............................................................................................. 285-5 Example Combination Chart ....................................................................................... 295-6 Gantt Chart with Amplifying Information ................................................................. 306-1 Beta Distribution with PERT Time Estimates ........................................................... 376-2 Example PDM Relationships/Constraints ................................................................ 396-3 Example PDM Constraints with Lag Time ................................................................ 406-4 Example PDM Activity Node ...................................................................................... 406-5 PERT Example ............................................................................................................... 426-6 PERT Example with Slack Time .................................................................................. 436-7 CPM Example ................................................................................................................ 446-8 PDM Example ................................................................................................................ 476-9 PDM Example—Example and Late Start and Finish Times ................................... 476-10 PDM Example with Lag Time ..................................................................................... 486-11 Network Schedule with Constrained Resources ...................................................... 496-12 Personnel Loading Chart .............................................................................................. 506-13 Revised Personnel Loading Chart .............................................................................. 516-14 Revised Network Schedule with Constrained Resources ....................................... 527-1 Line of Balance Technique ........................................................................................... 558-1 Total Cost Analysis for Selecting “Optimum” Program Duration ........................ 609-1 On-Screen Data Entry Using Gantt Chart Feature (AEC Software Fast Track Schedule) 68

TABLES6-1 CPM Example Time Estimates .................................................................................... 469-1 Project Management Software Functions and Criteria ............................................ 69

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1INTRODUCTION

1.1 OVERVIEW

In its simplest form, a schedule is a listingof activities and events organized by time.In its more complex form, the process ex-amines all program activities and their re-lationships to each other in terms of realis-tic constraints of time, funds, and people,i.e., resources. In program managementpractice, the schedule is a powerful plan-ning, control, and communications tool that,when properly executed, supports timeand cost estimates, opens communicationsamong personnel involved in program ac-tivities, and establishes a commitment toprogram activities.

A key aspect of program management plan-ning, scheduling is integral to a program’sacquisition strategy and to risk manage-ment, financial, and technical managementplans. In addition, scheduling is an impor-tant element of the other management func-tions: organizing, staffing, controlling, andleading. For example, controlling is per-formed to keep abreast of program execu-tion. To achieve this goal, it is necessary toknow whether the program is behind, on,or ahead of schedule, and what adjust-ments are necessary to keep the programon schedule once it’s back on track.

Why do Program Managers (PMs) sched-ule? The simple answer is they need a roadmap for all program players. In reality,scheduling can accomplish far more thanproviding a list of activities and times.

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Effective scheduling supports the follow-ing key program management activities:

• Provides the basis for effective com-munications within the government teamand with contractors,

• Identifies a baseline for program statusmonitoring, reporting, and program control,

• Facilitates management, and

• Provides the basis for resource analysisand leveling, exploration of alternatives,and cost/time tradeoff studies.

On the other hand, poor scheduling canadversely impact a program in a numberof areas. Haphazard schedules make itdifficult, at best, to determine a realisticcompletion date and to efficiently allo-cate resources to the entire program. Thiscreates financial problems—escalation ofcosts, increased support costs, delayedreturn on investment, funding cuts, orprogram termination.

Since scheduling is a powerful planning,control, and communications tool avail-able for program management, PMs musthave a good working knowledge of sched-uling practices and applications (such asGantt, milestone, and network schedules)in order to achieve program goals. PMswill not always have to construct detailedschedules, but they must be able to under-stand and analyze schedules created by

others (e.g., contractors) to successfullymanage a program. Since scheduling is anintrinsic and indispensable element of themanagement process, it is treated withinthe context of program management.

1.2 PURPOSE OF THIS GUIDE

This guide is an introduction to sched-uling. It is meant for people who alreadyhave some experience in program man-agement and those who seek to learn moreabout the subject. It is not a detailedtreatment of the subject, but instead, ex-plains how scheduling fits into the overallprogram management effort and how toaccomplish schedule planning. It also il-lustrates different scheduling conceptsand techniques and how they can be ap-plied and analyzed to manage effectively.Finally, it is intended as a road map toother useful and more comprehensivedocuments and texts on the subjects ofproject management, planning, and sched-uling that are available in the literature.

1.3 GUIDE CONTENT

In order to provide a suitable context forthe topic of scheduling, Chapter 2 pro-vides an overview of both program man-agement and the acquisition process andthe role scheduling plays in each.

Chapter 3 expands on the role of schedul-ing in program management and addressesthe following topics: work breakdownstructure, integrated master plans andschedules, and earned value management.It concludes with a discussion of schedulepreparation and schedule risk.

Chapter 4 introduces the topic of schedul-ing techniques with a general discussion of

the various types of schedules and howand why they evolved. This chapter is aprecursor for Chapters 5, 6, and 7, whichpresent a more detailed discussion ofthe key schedule types. These chaptersfocus on Gantt and milestone schedules,network schedules, and productionschedules.

Chapter 8 introduces the concept of timemanagement as it relates to the programand to the PM. Chapter 9 presents thesubject of automated project planning toolsand summarizes some of the desirable fea-tures of currently available software prod-ucts. In addition to an overview describingthe types of automated tools available, thischapter provides some suggestions on howto find and evaluate the latest products.The chapter concludes with a summary ofinformation sources that will be useful forfurther inquiry.

1.4 OTHER SOURCES OF DATA

As previously noted, this guide is intendedas a primer. There is a considerable body ofliterature on the subject of scheduling.Much of it is of an academic nature notspecifically keyed to defense acquisition.A number of these texts are listed in theBibliography Appendix of this guide. Ad-ditionally, an enormous amount of rel-evant information can be secured by search-ing the web using some of the popularsearch engines.Of particular use to PMs is the DefenseAcquisition Deskbook, available on theInternet (http://www.deskbook. osd.mil).The Deskbook includes a database contain-ing mandatory and discretionary policydocuments, Department of Defense andcomponent discretionary practices, soft-ware tools and descriptions, front-line wis-dom and advice, and sample formats.

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2PROGRAM MANAGEMENT AND

THE ACQUISITION PROCESS

2.1 PROGRAM MANAGEMENT OVERVIEW

The Department of Defense (DoD) consid-ers program management to consist of thetasks and activities that must be done inorder to design, develop, field, and sup-port a weapons system. DoD directivesdescribe an Acquisition Program as: “Adirected, funded effort that is designed toprovide a new, improved, or continuingweapons system or automated informa-tion system (AIS) capability in response toa validated operational need.”1 DoD con-siders the “program” to include the ele-ments of the acquisition process, such asthe planning, programming, and budget-ing process, and the design, development,and production of the system. Practicallyspeaking, a DoD program consists of acombination of organizational resources,assembled to create a weapons system tomeet a specific operational requirement.

Four key considerations typically involvedin a program are:

• Cost to produce the system,

• Time required to complete the effort,

• Capability/technical performance re-quired to meet needs, and

• Contribution of the system to the over-all defense operational and strategic plans.

For purposes of this guidebook, ProgramManagement consists of the planning, or-ganizing, staffing, controlling, and leading(POSCL) management functions. Otherfunctions sometimes included in a pro-gram management context are scheduling,budgeting, monitoring, directing, andmaintaining consensus and support. Forthis guidebook, these latter functions areconsidered subcategories of the basic fivefunctions, when appropriate.

• Planning addresses the program mis-sion, objectives, goals, and strategy andincludes all management activities that re-sult in selection of a course of action.

• Organizing considers the resources in-volved and how are they related. This func-tion addresses the alignment of people,funds, equipment, facilities, etc., and thestructure of the organization in order tomeet program goals; it identifies:

− Authority—The power to make finaldecisions

− Responsibility—The obligation to per-form assignments

− Accountability—The state of beinganswerable for the completion of anassignment.

• Staffing addresses the qualificationsand special skills that may be required

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for persons assigned to each position inthe program and the time phasing of as-signments.

• Controlling is the function during whichthe manager monitors, measures, evalu-ates, and corrects program activities to en-sure that actual operations conform toplans.

• Leading is the process whereby oneindividual exerts his/her influence overothers in a group. Directing, an element ofleadership, is the process of implement-ing, through the talents of others, the plansto meet program objectives. This includestraining, supervising, delegating, motivat-ing, counseling, and coordinating.

In a broad sense, the planning phase in-cludes the tasks associated with definingthe work requirements, specifying the quan-tity and quality of work, identifying re-sources, and organizing them to best carryout the program. Likewise, the manage-ment or execution phase includes the tasks ofmonitoring progress, comparing actual topredicted outcomes, analyzing the impactof differences between planned and actualachievements, and adjusting the programas necessary.

2.2 THE EVOLUTION OFPROGRAM MANAGEMENT

Formal program management came to theforefront in the late 1950s. The need todevelop and implement a managementapproach to manage large-scale militarysystems, both weapons and support sys-tems, stimulated the government and aero-space industry to devise the means to planand execute complex programs. As thecost of weapons systems increased and theintensity of the Cold War grew, DoD also

felt the need to predict the cost, schedule,and performance of its new systems. Mili-tary organizations (predecessors of cur-rent “acquisition” organizations), in conjunc-tion with defense contractors, developedmuch of the early theory and practices ofprogram management as new technolo-gies emerged.

The use of “task teams” or program teamsand other organizational entities led to theemergence of a program management phi-losophy for integrating activity in organiza-tions. As the program management disci-pline evolved, organizations developedspecial techniques for planning, organiz-ing, staffing, controlling, and leading pro-grams to integrate those activities from afocal point in the organizational structure.Moreover, program management ad-dressed the elements of technical perfor-mance, cost, and schedule on a continualrather than one-time basis in the evolutionof a program and considered them withinthe context of an organization’s operational(short-term) and strategic (long-term)objectives.

DoD has recently improved managementwith the introduction of the concept ofIntegrated Product and Process Develop-ment (IPPD) and Integrated Product Teams(IPTs). IPPD integrates all acquisition ac-tivities to optimize system development,production, and deployment. Key to thesuccess of this concept are the IPTs, com-posed of qualified and empowered repre-sentatives from all appropriate functionaldisciplines who work together to identifyand resolve issues. IPTs are the founda-tion for program management. One of thetenets of IPPD is the use of event-drivenscheduling, which relates program eventsto their accomplishment and accomplish-ment criteria. Its use reduces risk by

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ensuring that product and process matu-rity is incrementally demonstrated prior tobeginning follow-on activities.

2.3 THE ACQUISITION PROCESSAND SCHEDULING

For the management of programs, the DoDacquisition process provides a frameworkthat consists of a series of phases and mile-stones. The phases are a logical means ofprogressively translating broad missionneed statements into well-defined system-specific requirements and ultimately intooperationally effective, suitable, and sur-vivable systems. Each phase is designed,among other things, to manage/reduce therisks, ensure affordability, and deliver thesystem to the user as soon as possible.Milestones are the points in time wheredecision makers evaluate the status of theprogram and determine if the programshould proceed to the next phase. Prudentconsideration of schedule implications isimportant in all phases of a program.

Milestone Decision Authority (MDA) andService acquisition officials are encouragedto tailor programs to eliminate phases oractivities that result in little payoff in termsof fielding time or cost. To effectivelytailor a program, managers must under-stand scheduling, resource availability andallocation, and the risk associated with thetailoring.

An acquisition strategy defines the busi-ness and technical management approachto meet objectives within schedule andprogram constraints. A primary goal is tominimize the time and cost of satisfying avalid need, consistent with common senseand sound business practices. A PM pre-pares a preliminary acquisition strategy atMilestone 0 and updates the strategy to

support each milestone decision by de-scribing activities and events planned forthe upcoming phase and relating the ac-complishments of that phase to theprogram’s overall, long-term objectives.The acquisition strategy is first formallyapproved and published at MSI, ProgramInitiation. It provides a master schedule forresearch, development, test, production,fielding, and other activities essential toprogram success. This master schedulealso serves as the basis for formulatingfunctional plans and schedules.

As a program evolves through subsequentphases, new information becomes avail-able that permits refinement of schedulesand assignment of resources. Understand-ing of program risk becomes more specificas the system under development is de-fined, thereby allowing identification ofrisk-handling initiatives and their effect onschedule. Schedule considerations are anintegral part of any Source Selection pro-cess, from preparation of the Request forProposal (RFP) through proposal evalua-tion. After contract award, the scheduleserves as a basis to determine progress andassess the need for management action.

Government developers should design theircontracts with industry to allow time formilestone decisions, permit demonstrationof exit criteria in time to support milestonereviews and to reflect expenditure of moneywith the program’s funding profile. A goodacquisition strategy allows fiscal controlwithout delaying the acquisition decisionsor contracts while adequately consideringrisk. In other words, it reflects thoughtfulschedule and resource planning.

As a key element of the planning proess, PMsmust update the schedule as more is learnedabout the program and as changes occur.

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With each new update, program cost, time,and requirements may change. PMs mustrespond by changing the mix and level ofresources and continuously updating theprogram plan and the schedule as needed.

2.4 RISK MANAGEMENT AND SCHEDULING

DoD defines risk management as “the actor practice of controlling risk. It includesrisk planning, assessing risk areas, devel-oping risk-handling options, monitoringrisks to determine how risks have changed,and documenting the overall risk manage-ment program.”2 As part of their responsi-bility to manage risk, PMs must considerrisk in their planning and scheduling prac-tices. Risk management is concerned withthe identification of uncertainties thatthreaten cost, schedule, and performanceobjectives, and the development and imple-mentation of actions to best deal with thoseuncertainties.

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ENDNOTES

Risk management and scheduling areclosely tied. Consideration of one requiresa reassessment of the other. For example,in creating the strategy and plans to handleprogram risk, a PM must con-sider how the approach affects the pro-gram schedule. Similarly, any tradeoffsbetween cost and performance must takeinto account schedule implications. Con-versely, any change to the program sched-ule must consider the impact on the overallprogram objectives and on cost and perfor-mance. The challenge is to develop a planthat balances risk, cost, schedule, and per-formance.

Schedule risk is defined as the likelihoodand consequences of failing to meet theprogram schedule, and it is an integral partof program risk. This topic is covered inChapter 3.

1DoDD 5000.1, Defense Acquisition, March 15, 1996. (Being revised and updated as of 1 January 2000)

2Ibid.

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As discussed in the previous chapters,scheduling is one of the most powerfultools available to the PM, and its effectiveapplication is essential to program suc-cess. While it is a key element in perform-ing all program management functions, itis also critical to the accomplishment ofplanning and controlling managementfunctions. This chapter discusses schedul-ing in the context of these two functionsand addresses the essential elements andconsiderations in schedule planning.

3.1 PROGRAM PLANNING ANDSCHEDULING

Program planning is the process of deter-mining what needs to be accomplished, bywhom, when, and under what resourceconstraints. It is arguably the most impor-tant of the program management functions.Without a sound and comprehensive plan,it is virtually impossible to develop a mean-ingful budget, effectively organize and staffthe program office, direct the actions of theprogram office, or monitor and control theprogram. In addition to determining the“what, where, who, with what, and when”of a program, planning also helps to iden-tify risk areas and ways to handle the risk,and establishes the program baselines.

There are a number of products of theplanning process. Among them are:

• Acquisition Strategy—This is the com-prehensive, integrated plan the programwill follow. It provides an overall concept

of the program that functional plans willlay out in greater detail and reflects thestrategy that will be followed to meet pro-gram objectives and to handle risk in theprogram. The acquisition strategy in-cludes a program structure/schedulewhich depicts a visual overview and pic-ture presentation of the acquisition strat-egy. This schedule is a single diagramsimilar to the diagram shown in Figure 3-3,and defines the relationship among acqui-sition phases, decision milestones, solici-tations, contract awards, systems engineer-ing design reviews, contract deliveries, testand evaluation activities, production re-leases, and operational deployment objec-tives. It includes quantities to be procuredand delivered by fiscal year by phase interms of prototypes, engineeringdevelopmemt models, low-rate intitial pro-duction and full-rate production. The pro-gram structure/schedule is a key decisionreview/milestone document; it summa-rizes the program and is built from manyother more detailed schedules found infunctional plans such as test and evalua-tion, contracting, etc. It is sometimes re-ferred to as the Master Program Schedule(MPS). In addition to this top level struc-ture/schedule, the PM may deem it neces-sary to have more detailed program man-agement Integrated Master Plans (IMP) andIntegrated Master Schedules (IMS) pre-pared and submitted by the contractorduring the proposal process. See the DSMCAcquisition Strategy Guide1 for informationon structuring, developing, and executingan acquisition strategy.

• Functional Plans—These are the de-tailed plans that lay out the approach tobe taken in the different functional areas.Examples include: the Test and Evalua-tion Master Plan (TEMP) and Command,Control, Communications, Computers, andIntelligence (C4I) Support Plan, which arerequired; and the Systems EngineeringMaster Plan (SEMP), Logistics SupportPlan (LSP), etc., which are optional.

• Work Breakdown Structure (WBS)—The WBS provides a basic framework foridentifying each element of a project inincreasing levels of detail. In essence, itdescribes the way work is performed. TheWBS also provides a coherent method forreporting progress toward plan goals.

• Integrated Master Plan (IMP)—TheIMP is an event-based plan depicting theoverall structure of the program and thekey processes, activities, and milestones.It defines accomplishments and criteria foreach event.

• Integrated Master Schedule (IMS)—The IMS shows the detailed tasks andtiming for events in the IMP and depictsthe logical progression of events through-out the program. These tasks should bedirectly traceable to the IMP and the WBS.

• Schedules—A series of schedules aredeveloped during the planning process,all of which are derived from the IMS.These schedules are developed to showthe details required to complete key activi-ties and milestones.

• Budget—The budget reflects the costof the integration of the scope, schedule,and resource plan for accomplishing thework.

Scheduling is a critical element in the plan-ning process. In addition to being an out-put of the process as discussed above, italso contributes to the development of theother outputs. The early involvement ofpeople who are knowledgeable and experi-enced in scheduling techniques can contrib-ute to the effective translation of strategicconcepts and ideas into detailed logic dia-grams, depicting the program activitiesand relationships among activities. Thiscan be very useful in developing budgetand detailed functional plans, especiallyin identifying the required resources andleveling them throughout the activities.

The WBS and the IMP/IMS are importantconcepts used in the scheduling processand are described in more detail in thefollowing sections.

3.2 WORK BREAKDOWN STRUCTURE

During the 1960s, the impetus to develop atool to help project managers define aproject in a cohesive way gave rise to thedevelopment of the WBS. WBS use has notbeen confined to the DoD and its contrac-tors; rather, it is now used in many com-mercial enterprises. Several years after theemergence of the WBS concept, DoD pub-lished a WBS standard for DoD acquisitionorganizations as well as their contractors touse: MIL-STD-881B. This standard has beensuperseded by a handbook, MIL-HDBK-881, dated 2 January 1998. It contains muchof the same information as its predecessorbut is not directive in nature and is forguidance only.

MIL-HDBK-881defines a WBS as:

• A product-oriented family tree com-posed of hardware, software, services, data,and facilities. The family tree results from

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high cost or high risk. In that case, the WBSshould be taken to a lower level ofdefinition.

WBS's apply to seven specific categories ofdefense materiel systems: aircraft; elec-tronic/automated software; missile, ord-nance; ship; space; and surface vehicle.The WBS should be developed and main-tained based on the systems engineeringefforts throughout the system’s life cycle.

Figure 3-1 is an example of a level 3 program

systems engineering efforts during the ac-quisition of a defense materiel item.

• A WBS displays and defines the prod-uct, or products, to be developed and/orproduced. It relates the elements fo workto be accoomplished to each other and tothe end product.

• A WBS can be expressed down to anylevel of interest. However, the top threelevels are as far as any program or contractneeds to go unless the items identified are

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Figure 3-1. Generic Aircraft System Program WBS

Level 1 Level 2 Level 3Aircraft System Air Vehicle

Systems Eng/Program MgmtSystem Test andEvaluation

Training

Data

Peculiar SupportEquipment

Common SupportEquipment

Operational/SiteActivation

Industrial Facilities

Initial Spares &Repair Parts

AirframePropulsionA/V Application S/WA/V System S/WNavigation/GuidanceCentral ComputerFire ControlData Display and ControlsSurvivabilityReconnaissanceAutomatic Flight ControlCentral Integrated CheckoutAntisubmarine WarfareArmament Weapons DeliveryAuxiliary Equipment

Development Test and EvaluationOperational Test and EvaluationMock-upsTest and Evaluation SupportTest Facilities

EquipmentServicesFacilities

Technical PublicationsEngineering DataManagement DataSupport DataData Depository

Test and Measurement EquipmentSupport and Handling Equipment

Test and Measurement EquipmentSupport and Handling Equipment

System Assembly, Installation andCheckout on SiteContractor Technical SupportSite ConstructionSite/Ship/Vehicle Conversion

Construction/Conversion/ExpansionEquipment Acquisition orModernizationMaintenance (Industrial Facilities)

Initial Spares and Repair Parts

Prime Mission System

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WBS for an aircraft system. The WBS ap-proach provides a powerful technique forscoping a project in a manner that providesmanagement with insight into project re-quirements and performance from thevery top, or systems level, to the lowestlevel of definition of a work product. Plan-ning work using the WBS approach servesas the basis for both estimating and sched-uling resource requirement.

3.2.1 Integrated Master Plans/Schedules

The IMP is a very effective tool of programmanagement. It is the contractor's event-based plan for accomplishing the State-ment of Objectives (SOO) and Statement ofWork (SOW). It identifies the key activi-ties, events, milestones, and reviews thatmake up the program. A program IMP isprepared initially by the contractor and

provides the basis for development of sub-ordinate IMPs and other functional plans.It also identifies those events and activitiesthat will be included in the IMS.

The IMS is a networked multi-layeredschedule generated by the contractor thatbegins with all identified IMP events, ac-complishments, and criteria. It shows theexpected start and finish dates of theseevents. It contains all contractually re-quired events/ milestones such as reviews,tests, completion dates, and deliveriesspecified in the program WBS.

The IMP is prepared by the contractorduring the proposal process. It is main-tained by the government program officeand contractor through a collaborative ef-fort involving all the program “stakehold-ers.” In some cases, a preliminary IMPmay be developed by the government,

Figure 3-2. IMP/IMS Sample

Detailed Tasks1. Preliminary Design Complete2. Duty Cycle Defined

Requirement WBS Elements SOW Task

Integrated Master Plan

Integrated Master Schedule

3.1 Air Vehicle (WBS 1000)Design, develop, produceand verify, complete airvehicles, defined as airframepropulsion, avionics andother installed equipment.

Management Plan EventsPDR

Accomplishment Criteria1. a. Duty Cycle Defined b. Preliminary Analysis Complete

1. Preliminary Design2. Review

19XX 19XY 19XZProgram Events PDR CDR

1000 Air Vehicle1100 Airframe

1110 Wing

11n

System Specification

1000 Air Vehicle

1100 Airframe

Wing

with industry input, during pre-solicita-tion. The IMP defines contract requirementsstated in the RFP and contractors use it todevelop the IMS and detailed functionalschedules. These integrated schedules tietogether all program tasks by showing theirlogical relationships and any constraintscontrolling the start or finish of each task.This process results in a hierarchy of re-lated functional and layered schedulesderived from the WBS that can be used formonitoring and controlling programprogress. An example (suggested format)of an IMP/IMS for an aircraft developmentprogram is depicted in Figure 3-2. The IMSshould be expanded down to the level ofdetail appropriate for the scope and risk ofthe program. Programs with high riskshould show more detail in the IMS toprovide the visibility necessary to managerisk. A more detailed discussion of IMS's iscontained in Appendix A. A Data ItemDecription (DID) has been developed by theDepartment of Defense for the IMS; the iden-tification number is DI-MISC-81183A. ThisDID is at Tab 1 to Appendix A.

3.3 PROGRAM CONTROLLINGAND SCHEDULING

The controlling function contains all thoseactivities that a program manager under-takes in attempting to ensure that the ac-tual program conforms to the developedplan, to include the implementation of nec-essary action to get the program back onthe plan if possible. To control a program,the PM needs the means to monitor pro-gram progress against the established plan,or the program baseline. In its simplestform, the program schedule can serve as abaseline against which to measure progress.If there are indications that an activity isfalling behind schedule, this informationcan be used by the manager as a basis for

corrective action. However, consideringschedule information alone can be mis-leading. Successful management requiresthe integration of the technical, schedule,and cost aspects of a program. Thus, someform of integrated performance measure-ment is needed for monitoring and control-ling a program. The concept of earned valuemanagement provides such a capability.

3.3.1 Earned Value Mangement

Earned Value Management (EVM) is theuse of an integrated management systemthat coordinates work scope, schedule, andcost goals and objectively measures pro-gress toward these goals.2 The purpose ofEVM is to provide contractor and gov-ernment PMs with accurate data to moni-tor program execution. It is also intendedto provide an adequate basis for soundcontractor and government decision mak-ing by requiring that the contractor’s inter-nal management control systems producedata that: (1) indicate work progress; (2)properly relate cost, schedule, and techni-cal accomplishments; (3) are valid, timely,and able to be audited; and (4) provideDoD component managers with informa-tion at a practical level of summarization.

The DoD earned value process holds thecontractor responsible for effective imple-mentation of an EVM system. DoD does notprescribe a specific EVM system for con-tractors to use; instead, it has established aset of criteria that the contractors’ systemsmust meet to be acceptable. The require-ment to use an EVM system that meets thecriteria is dependent on the type and sizeof the contract. DoD Regulation 5000.2-Rdefines the contracts that must use such anEVM system as well as the criteria for anacceptable system. For contracts that do

11

not meet these thresholds, contractor man-agement information is provided to thegovernment using a Cost/Schedule StatusReport (C/SSR). This report should bebased on an underlying management sys-tem that uses an earned value approach fortracking progress. Such a system does nothave to meet the EVM criteria of DoD5000.2-R; however, the government shouldnegotiate with the contractor to ensure thatthe system does emphasize earned valuemethodology.

Basically, earned value relates resourceplanning to schedules and to technical per-formance requirements. All work (identi-fied in the Program and Contract WorkBreakdown Structures) is planned, bud-geted, and scheduled in time-phased“planned value” increments constituting aperformance measurement baseline. Aswork is performed, it is “earned” on thesame basis as it was planned, e.g., in bud-geted dollars or labor-hours. Planned value[budgeted cost of work scheduled (BCWS)]compared with earned value [budgeted costof work performed (BCWP)] measures thedollar volume of work planned versus theequivalent dollar value of work accom-plished. The difference, if any, is termedthe “schedule” or “accomplishment” vari-ance. Earned value (BCWP) comparedwith the actual cost of the work performed(ACWP) provides an objective measure-ment of cost performance. Any differenceis called the cost variance.

The three data points—BCWS, BCWP, andACWP—are outputs of the EVM system andare provided to the government on a monthlybasis. They, along with the schedule and costvariances, provide the basic informationneeded to determine program status at agiven time, and to identify the elements thatare driving each of the variances.

Analysis of these data points over timealso identifies trends that may affect orimpact the future performance for the re-mainder of the contract. This is important;it enables PMs to isolate causes of recur-ring variations and to take alternative ac-tions that will improve performance. Quan-titative techniques can also be applied toEVM data to predict program performanceat completion in terms of cost and sched-ule. The DSMC EVM Textbook3 providesdetailed information on the application ofEVM techniques.

Success of EVM techniques is dependent onseveral things, not the least of which iseffective and accurate contractor schedul-ing. EVM system criteria do not requirecontractors to use specific scheduling tech-niques. However, they do seek formality,consistency, and discipline throughout thescheduling process. The contractor's sched-uling system:

• Provides a summary or master sched-ule and related subordinate schedulesshowing vertical traceability from the mas-ter to the detailed schedules

• Identifies key milestones and activitiesand indicates significant constraints andrelationships

• Provides current status and forecast ofcompletion dates of scheduled work thatenable comparison of planned and actualstatus of program accomplishments

• Establishes a schedule baseline

• Provides horizontal traceability show-ing interrelationships among various ac-tivities.

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The scheduling baseline usually con-sists of a hierarchy of vertically inte-grated schedules, with each lower-levelschedule more fully identifying and ex-panding the tasks necessary to meet theprogram’s objectives. Generally, three setsof schedules are prepared:

• Master Schedule (MS)—The top-levelschedule that summarizes key programactivities and milestones and depicts thelogical progression of events throughout acontract. Program Structures/Master Pro-gram Schedules developed by the govern-ment PM reflect information contained inthe contractor's Master Schedule.

• Intermediate Schedules—The sched-ule that ties the MS to the detailed sched-ules. It allows for rollup of detailed sched-ules to summary levels that are useful formanagement.

• Detailed Schedules—The schedules atthe control account or work package level.Work packages must be distinguishablefrom each other and must include definitestart and completion dates. They are pre-pared by the contractor with governmentconcurrence.

3.4 SCHEDULE PREPARATION

As stated earlier, scheduling is a criticalelement of the planning process. Con-versely, planning is critical to the devel-opment of effective schedules. Near-termscheduling can and should be accom-plished in sufficient detail to supportmanagement at each level. Far-term, orrolling-wave, scheduling will be less pre-cise, accounting for the alternative pathsthat the program may take. As the pro-gram approaches each phase, the sched-ule for that phase will be fleshed out with

more detailed schedule information. Theschedule for the out-year phases will beadjusted based on the most current infor-mation. However, this should not be takenas a license to make easy changes in theschedule. Every effort should be made tomaintain the original schedule.

In all programs, there will always be arequirement to make tradeoffs betweencost, schedule, and performance. Cost in-cludes all resources—people, money,equipment and facilities. Performance in-cludes quality and supportability param-eters. The best schedule supports the besttradeoff between these competing de-mands, taking into account the risks thatare associated with each tradeoff and theimpact on the overall program.

The preparation of program schedulesshould be done within a formal structure.The procedures to be followed should bespecified, to include such things as soft-ware applications to be used, the formatsfor displays, and the type of symbols to beused. Also, clear lines of authority andresponsibility should be established. Theremainder of this section discusses the logi-cal steps that should be followed in pre-paring schedules, to include sources ofinformation, tools and techniques, and theoutputs of the steps. These steps are basedon those described in the Program Man-agement Institute’s Guide to the ProgramManagement Body of Knowledge.4 While theypresent a somewhat different approachthan the IMP/IMS method, they have ge-neric applicability over the range of plan-ning methods.

3.4.1 Activity Definition

This step involves the identification anddefinition of those activities that must be

13

accomplished to achieve the objectives.The WBS is a logical source for suchdescriptions. If a WBS is not available,more planning must be done in order toidentify project activities clearly. Otherinputs to the definition step are the pro-gram scope, historical information, pro-gram constraints and assumptions, andevents required by the Planning, Program-ming, and Budgeting System (PPBS), therequirements generation system, and DoDacquisition management process.

Decomposition and templates are tech-niques commonly used in activity defini-tion. Decomposition involves the succes-sive breakdown of program elements intosmaller, more manageable components,which eventually describe the activities tobe scheduled. This technique is essen-tially the same used in WBS development.A template is an activity list or WBS ele-ment from another similar program thatcan serve as a model for the current pro-gram and provide a starting point for de-fining specific activities.

The primary output of this step is the activ-ity list, which should contain a completedescription of each of the activities neces-sary to complete the program. This listshould be linked to the WBS, which shouldbe reviewed and revised/clarified as nec-essary to incorporate changes resultingfrom the activity definition process. Sup-porting details for each activity, such asconstraints and assumptions, should alsobe developed and documented.

3.4.2 Activity Sequencing

This step involves the accurate identifica-tion of constraints/relationships among ac-tivities and establishing the order in whichthe activities will be accomplished.

There are several inputs to this step:

• The activity list developed in the activ-ity definition step,

• The product description and character-istics,

• Mandatory constraints/dependencies,such as the fact that a prototype must befabricated before it can be tested,

• Discretionary constraints/depend-encies developed by the program manage-ment team based on “best practices” orspecific sequences desired by management,

• External dependencies, such as avail-ability of test sites, and

• Other constraints and assumptions.

A number of tools and techniques are use-ful in developing the logic diagrams thatreflect the desired activity sequencing.They include various network schedulingtechniques that are discussed in Chapters 4and 6. In addition, a number of schedulingsoftware programs develop activity se-quencing. Their selection and use are dis-cussed in Chapter 9.

The output of this step is a network dia-gram that reflects the sequence of activitiesbased on the inputs described above. Thisdiagram should be augmented with anarrative description of the sequencing ap-proach and a detailed discussion of anyunusual or complex sequences. Activitylists should be reviewed and revised toreflect any changes necessitated by activitysequencing.

3.4.3 Activity Duration EstimatingActivity duration estimating is the determi-

14

nation of the time required to complete theactivities that make up the program. Thisis one of the most difficult aspects of sched-ule development and should be performedby people who are most familiar with theactivity. Two key inputs to the estimationprocess are the resources required and as-signed for the activity and the capabilitiesof the resources assigned. Historical infor-mation from other programs and from com-mercial databases can also be helpful indeveloping accurate estimates.

The following techniques are commonlyused in estimating activity durations:

• Expert judgment guided by historicalinformation,

• Analogous estimating based on expe-rience of similar programs,

• Parametric estimating based on formu-las describing relationships among pro-gram parameters and time, and

• Use of simulation to develop distri-butions of probable duration of eachactivity.

The output of this step is an estimate of thelikely amount of time to complete eachactivity. These estimates should also in-clude a range of possible values, e.g., 3weeks ± 1 week, and a clear statement ofthe assumptions made in the estimationprocess.

3.4.4 Schedule Development

This step involves the development ofrealistic start and finish dates for eachactivity. An iterative process, scheduledevelopment takes into account activitysequencing, duration estimates, resource

requirements and availability, calendarsthat show when work can be performed,constraints, assumptions, and risk.

The output of this step is a set of sched-ules for the program. These include themaster program schedule and the support-ing detailed schedules, which should re-flect the best balance possible between com-peting demands of time and resources.They should also take into account the riskassociated with time, cost, and performancetradeoffs and the impact on the overallprogram.

A number of techniques and tools are usefulin developing schedules, many of which arecontained in various scheduling softwareapplications. Many of these applicationscontain the capability to perform varioustypes of mathematical analyses to calculatetheoretical start and finish dates for eachactivity based on the overall sequencing ofthe program activities. Two of the morecommonly known analysis techniques arecritical path method (CPM) and the Pro-gram Evaluation and Review Technique(PERT). They are discussed in greaterdetail in Chapter 6.

Other scheduling development techniquesthat are commonly used focus on scheduledevelopment in light of resource (time,people, funds, material) constraints. Thesetechniques provide the means to manage theaffect of these constraints through the com-pression of activity duration and the levelingof resources throughout activities. Schedulecompression and resource leveling are dis-cussed in more detail in Chapter 6.

3.4.5 Schedule Control

The final step in the schedule preparation

15

process is to identify schedule variations andto manage actual changes to the developedschedules. A schedule change control sys-tem that defines the procedures by whichchanges can be made should be establishedand integrated into the program’s overallchange control system. The schedulechange control system should address suchthings as the methods of schedule perfor-mance tracking and the approval processfor authorizing changes. The need for sched-ule changes can be caused by a number offactors, to include:

• Failure to achieve planned dates forspecific activities or events,

• Internal program management assess-ment and replanning, and

• External direction, such as reallocationof funding.

When evaluating these factors, it is im-portant to determine what, if any, sched-ule change is necessary. For example, ifan activity that is not on the critical path isnot completed as planned, it may not haveany effect on the overall program sched-ule. Consequently, it may not require anysignificant schedule change.

The schedule change control systemshould also include procedures for imple-menting schedule changes. Such proce-dures should address the requirement tokeep all program stakeholders, especiallythe users, advised of any significant sched-ule changes. They should also address theprocess for adjusting the schedule baselineand the overall program plan when neces-sary schedule changes are severe. Thechange control system can also serve as agood database of lessons learned. Conse-quently, information concerning sched-

ule variations, their evaluation, and thedevelopment of corrective actions shouldbe documented and made readily avail-able to members of the program’s man-agement team, and to other programs.

3.5 SCHEDULE RISK

In Chapter 2, we discussed the relation-ship between risk management and pro-gram scheduling. In this section, we dis-cuss the risk associated with the programschedule. Uncertainty exists in everyschedule. It is impossible to predict, withcomplete confidence, the length of timenecessary to complete an activity, meet amilestone, or deliver a system. Little in-formation exists in the early phases of aprogram, and planners must rely on per-sonal experience and the estimates of ex-perts. As a program progresses throughthe acquisition cycle, more informationbecomes available. Schedules developedin the latter phases of a program are basedon more information and analyses, butthey still lack complete certainty. Uncer-tainty introduces the element of risk in theplanning process. Schedule risk is thelikelihood of failing to meet schedule plansand the effect of that failure.

When creating a schedule, or when deter-mining overall program risk, the PM mustassess the risk associated with the sched-ule. One technique for assessing this sched-ule risk involves estimate contributionsfor each activity’s duration and aggregat-ing these distributions using a Monte Carlosimulation or other analytical tools. Theresulting program-level schedule is thenanalyzed to determine the actual sched-ule risk and to identify the schedule riskdrivers.

This technique uses a range of times that itwill take to complete each activity instead

16

17

of single-point estimates. This approachresults in a more realistic estimate of sched-ule risk because it accounts for much of theuncertainty inherent in the use of single-point estimates. Their use invariably leadsto underestimating the time required tocomplete the program and, therefore,schedule overruns, primarily because thepoint estimates do not adequately addressthe uncertainty inherent in the individualactivities.

This range of values for each activity de-fines a probability distribution for the du-ration of the activity. These distributionsare then combined to determine the pro-gram-level schedule estimate. This ap-proach enables PMs to estimate early in aprogram if there is a significant likelihoodof overrunning the program schedule andby how much. It also identifies programactivities that are on the “highest risk path.”

This technique can be used in any acqui-sition phase beginning with the comple-tion of the first statement of work. Theschedule probability distribution functionfor each key activity should be developedas soon as the activity is included in themaster schedule. The distribution func-tions should be periodically reviewed andrevised, if necessary, at least once per phase.

The technique should be applied by a smallgovernment-industry team consisting ofschedule analysts and technical expertswho understand the significance of previ-ous risk performance assessments. See theDSMC Risk Management Guidebook5 or theDefense Acquisition Deskbook, Section 2.5.2.46for more details on the application of thistechnique.

3.6 SUMMARY

Scheduling is critical to the successful exe-cution of the planning and controllingfunctions of program management. In theplanning phase, it contributes to thedevelopment of detailed functional plans

and budgets and to identification and allo-cation of required resources throughoutprogram activities. During this phase isdeveloped a set of integrated multi-lay-ered schedules that tie together all pro-gram activities, showing their logical rela-tionships and any constraints. The level ofdetail developed for these schedules de-pends on program scope and risk. Thisprocess provides a hierarchy of functionaland layered schedules that can be useful inmonitoring and controlling programprogress.

Effective program control depends on someform of integrated cost, schedule, and tech-nical performance management, such asthe earned value management system(EVMS). Effective scheduling is key to thesuccess of this technique. EVMS criteria donot dictate the use of specific schedulingtechniques. However, they do seek for-mality, consistency, and disciplinethroughout the scheduling process.

A five-step process for schedule prepara-tion that is commonly used in program/project management includes:

• Activity definition,

• Activity sequencing,

• Activity duration estimation,

• Schedule development, and

• Schedule control.

Risk is inherent in all programs, and sched-uling is one element of risk. Uncertaintyintroduced in estimating the duration ofeach activity causes most schedule risk.PMs must assess the likelihood of failingto meet schedule plans and the impact ofthat failure. Probabilistic techniques haveproven to be very useful in conductingthese assessments.

1 Defense Systems Management College, Acquisition Strategy Guide, Fort Belvoir, VA, January 1998.2 Defense Systems Management College, Earned Value Management Textbook, Fort Belvoir, VA, April 16, 1998,3 Ibid.4 Program Management Institute, A Guide to the Program Management Body of Knowledge, Newtown Square, PA,

1996.5 Defense Systems Management College, Risk Management Guidebook, Fort Belvoir, VA, May 1999.6 Information on schedule risk techniques is in the Risk Assessment Techniques of the Front Line Wisdom

& Advice portion of Section 2.5.2.4, Defense Acquisition Deskbook.

ENDNOTES

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Figure 3-3. Program Schedule/Structure (Example)

PROGRAM STRUCTURE/SCHEDULE (EXAMPLE) FY01 FY02 FY03 FY04 FY05 FY06 FY07 FY08 FY09 FY10 FY11 FY12 FY13 FY14

ContractAward

RDT&EProcurementO&MMILCONTotal

C&TDCAD

Sys Int Sys DemoSystem Devel & Demo

A DecRev

B

PrototypeCompetition

IPR

FRPC IOC

B FRP IOC

FRP IOCCB

SD LRIP PROD Blk IIPROD

Blk IIISD

Blk IIIPROD

C

MilestoneReviews& Phases

TechnicalReviews

Developmental& Operational

Testing

DeliveriesOT FOT&E

EDM

EOA

LRIP Production

LRIP Prod & Deployment Operations & Support

Block II

Block III

(eng dev models)

DT&E

IOT&E

Full-RateCE

LFT&E

C&TD SI

ASR SRR PDRSFR CDR FCA/SVR

PCA CDR PCA CDR PCA

Blk IISD

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4SCHEDULE TYPES AND THEIR EVOLUTION

4.1 INTRODUCTION

Previous chapters of this guide stress thepoint that scheduling is an intrinsic, indis-pensable part of program management anda key output of the planning function ofthat process. They also describe the rela-tionship between the program Work Break-down Structure and scheduling, and intro-duce the concepts of the Integrated MasterPlan and the Integrated Master Schedule.Properly prepared and accurate schedulesare invaluable tools in the overall manage-ment of programs. They provide a roadmap of where the project is going, theresources required to accomplish the vari-ous project tasks, a means to determineprogress, and an effective way to presentstatus information. This chapter containsinformation on the various types of sched-ules generally in use today, their character-istics, advantages and disadvantages, andhow they have evolved. Subsequent chap-ters provide more detailed information oneach of the schedule types, along with in-formation on the selection and use ofscheduling software.

4.2 SCHEDULE TYPES

Schedules can be presented in a variety ofways. Regardless of how they are dis-played, schedules essentially convey in-formation concerning one (or a combina-tion) of the following categories:

• Activities or tasks to be accomplishedover a period of time, and

• Events or milestones, that take place ata point in time, such as a Defense Acquisi-tion Board (DAB) milestone review.

Dependencies or constraints among activi-ties or events.1

Currently, four types of schedules are incommon use and depict the categories ofinformation described above. They are theGantt or bar chart, the milestone schedule/chart, the network schedule, and the pro-duction schedule. The evolution, character-istics, and uses of each of these schedulesare described in the following paragraphs,and a more detailed treatment of each ofthem is contained in subsequent chapters.

4.2.1 Gantt and Milestone Charts

Gantt charts and milestone charts are nor-mally combined to show a program’sschedule; therefore, they are discussed inthis context. The Gantt chart is used toprovide information concerning activities.It is commonly referred to as a bar chart,since it depicts an activity as a horizontalbar imposed over a time-line, or calendar.It shows the planned start and finish datesfor the activity and may provide informa-tion about task progress, including sched-ule slips or gains. Figure 4-1 is an exampleof a simple Gantt chart that shows theplanned schedule for four activities.Progress in accomplishing each activitycan be shown on each of the bars, as shownby the shaded portions of activities 1 and 2.

Activity

Identify User Requirements

Identify Performance Requirements

Identify Interface Requirements

Prepare SW Requirements Spec

Jan Feb Mar Apr May Jun

Legend

PlannedActual

20

The Gantt chart was the first formal sched-uling technique developed. It dates backto the early 20th century when Henry L.Gantt first introduced it while working atthe Frankford Arsenal during World WarI. It was developed to provide a moreformal and systematic way to scheduletasks when time was an imprtant factor.

The Gantt chart has survived in its basicform to this day and continues to bewidely used as a scheduling tool at alllevels within organizations. Its valuelies in its simplicity and its ability toconvey considerable information in aclear and concise manner. In the past, theprincipal shortcoming of the traditionalGantt chart was its inability to clearlydepict dependencies or constraintsamong activities, making it difficult toanalyze schedules and optimize the allo-cation of resources to the activities. Somescheduling software programs now makeit possible to show relationships, thereby

improving its utility. The Gantt chart isvery useful in reporting project status andin managing individual activities or simpleprojects with few tasks.

Subsequent to the development of the Ganttchart, planners and managers used a simi-lar approach to depict information aboutsignificant project events, focusing on spe-cific points in time. These events repre-sented project milestones—hence the in-troduction of the milestone chart. The mile-stone chart shows when an event is sched-uled and when it is actually accomplished.Figure 4-2 is an example of a milestonechart showing the status of four events;each of these events represents the comple-tion of the four activities shown in theexample Gantt chart in Figure 4-1.

Like the Gantt chart, the strength of thismilestone chart as a scheduling techniquelies in its relative simplicity and its abilityto concisely display project information,

Figure 4-1. Gantt Chart Example

Now

21

especially at the “big picture” level. How-ever, it does have shortcomings that limitits effectiveness in day-to-day project man-agement. As shown in Figure 4-2, the mile-stone chart can depict the events corre-sponding to the completion of an activity.

However, it does not reflect the progress inaccomplishing the activity. In this case, amanager relying on this milestone chartinformation could be surprised if theplanned completion date is not achieved.With no warning or indicators of scheduleslippage, the manager loses any flexibilityin attacking the underlying problems caus-ing the slippage. This shortcoming can becompensated for by the addition of interme-diate events or through the use of combinedGantt and milestone charts. This is discussedin more detail in the next chapter.

Another weakness of the milestone chart isthe difficulty to clearly visualize therelationships, dependencies, and con-straints among the various project/pro-gram activities and events. In spite of theseshortcomings, the milestone chart can bean effective way of presenting the projector program status at higher levels of man-agement review.

Perhaps the biggest shortfall of the Ganttand milestone charts is that neither ofthem, nor the combination of both, allowdetailed schedule analysis. However,every PM must know and understandGantt and milestone charts for two simplereasons: everybody uses them, and nor-mally, one of the first steps in the planningprocess is to construct a schedule using aGantt chart.

4.2.2 Network Schedules

Network scheduling was developed toovercome the primary shortcoming of theGantt and milestone charts—the inabilityto clearly portray the relationships, depen-dencies, and constraints among the projectactivities and events. A network scheduleis a graphical display of a project, includ-ing a representation of these relationships.Figure 4-3 shows an example of a networkschedule for a simple project.

In this example, the lines represent projectactivities A through H; the nodes repre-sent the events associated with the begin-ning and end of the activities. The net-work shows the following constraints

Figure 4-2. Milestone Chart Example

Event

User Requirements Identified

Performance Requirements Identified

Interface Specs Identified

SW Requirements Spec Completed

Jan Feb Mar Apr May Jun

Legend

PlannedActual

among the activities: activity A must becompleted before activities B, C, or D canbegin; B must be completed before E canbegin; F cannot begin until D is completed;G cannot begin until C and E are done, andH cannot begin until F and G are com-pleted. In addition to showing this type ofsequencing constraints, network schedulescan also show the time and resourcesplanned for each activity and thus providemanagers with a mechanism to monitorand control the project. A later chaptercovers network schedules in detail.

The advent of network schedules can betraced back to the 1920s and the evolu-tion of operations research. Analysts re-alized the inability to depict dependen-cies and constraints was a major short-coming of existing scheduling techniques,and attempted to solve the problemthrough the application of network theory.The translation of this theory into a usablescheduling tool was hindered by the in-ability to process network-related datain a timely fashion. The development ofthe computer provided the means to au-tomate this data processing and, by the1950s, the concept of network scheduling

was being applied to large, complex pro-grams. The first major network schedul-ing technique developed was the Pro-gram Evaluation and Review Technique,or PERT, which was used as a manage-ment tool for scheduling and controllingthe Navy’s Polaris missile program. PERTenables managers to visualize the entireprogram, see interrelationships and de-pendencies, and recognize when andwhere delays are acceptable. One of thekey features of PERT is the use of prob-ability techniques to develop a set oftime estimates for each program activity,making it particularly well-suited for pro-grams where it is difficult to make accu-rate estimates with high confidence. Con-current with the development of PERT,the construction industry developed anetwork scheduling system based on theconcept of critical path. A project’s criti-cal path is the most time-consuming routethrough the network activities that mustbe completed in order to finish the project.This approach, named Critical Path Method(CPM), was designed to focus on perfor-mance time and total program cost. Somepublications refer to CPM as the ArrowDiagram Method (ADM).

Figure 4-3. Network Schedule Example

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A

B

C

D

E

F

G H

PERT and CPM scheduling techniques havemany similarities. For example, each showsthe relationships among activities andevents, both include the project’s criticalpath, and the structure of each allows analy-sis of the tasks to be done, resources as-signed to do them, and the time associatedwith each task. Both techniques use nodesto represent events (beginning and end ofactivities) and lines to represent the activi-ties.

A third network scheduling technique is thePrecedence Diagram Method (PDM), whichwas developed subsequent to the PERT/CPM techniques. Its function is to permit amore accurate depiction of relationshipsamong various activities than is possibleusing the other two techniques. PERT/CPM techniques are essentially limited to“finish-start” relationships (i.e., activity Bcannot start until activity A is completed).The PDM technique can depict other rela-tionships that permit a more accurate andrealistic portrayal of the program’s activi-ties, such as “start-start” (i.e., activity B can-not start until activity A starts). The tech-nique accomplishes this through the use ofnodes to depict activities and lines to depictrelationships. These three techniques arediscussed in greater detail in Chapter 6.Network scheduling techniques providemanagers with a powerful tool for schedul-ing and controlling their programs/projects.In general, they permit the graphic por-trayal of project activities and relationshipsamong the activities. This provides thebasis for determining the project’s criticalpath, predicting shortages, and identifyingpossible reallocation of resources to solveproblems. Through the use of readily avail-able software, network schedules are fairlyeasy to update and rework, thus providingmanagers with current program/project sta-tus information and control over activitiesand schedules.

In spite of the strengths of network schedul-ing techniques, there are some limitations.The value of network schedules is directlydependent on the validity of the time esti-mates for each activity. In addition, it issometimes difficult to accurately portrayall activities and relationships, especiallyfor very large, complex programs. Thus,considerable “up front” work is requiredto develop an effective network schedule.Detailed networks, once developed, tendto be the focus of management attentionwhen, in fact, there will undoubtedly beother factors not on the display that willrequire management attention.

4.2.3 Production Schedules

Production scheduling involves the plan-ning, execution, and control of repetitiveactivities, such as the manufacture of alarge number of identical items. Efficientproduction requires the proper balance ofmaterials, facilities, and personnel skills.It also requires a means to monitor theproduction process.

The Line of Balance (LOB) technique, whilenot truly a scheduling tool, is such a moni-toring technique that can provide earlywarning of potential problems that canaffect program schedule. It is especiallyuseful for monitoring repetitive processeswhere it is essential to balance inventoryacquisition with the production processand delivery requirements. The LOB tech-nique consists of four elements: (1) objec-tives of the program, i.e., contract sched-ule and actual deliveries; (2) productionplan; (3) current program status or inven-tory; and (4) a comparison between wherethe program is and where it’s supposed tobe, (that is, program inventories versusthe LOB). These elements are discussedin more detail in Chapter 7.

23

The origin of LOB is not clear, but it isbelieved it was developed to help managedefense-related contracts in the 1940s and50s. It is still used today in both defense andcommercial industry. While governmentPMs or their staffs will probably not need todirectly develop or apply the LOB tech-nique, they should understand it and real-ize that it can be a valuable tool for contrac-tors to monitor the status of productioncontracts and to present status information.

This technique can point out problems be-fore their impact on finished product deliv-eries shows up, thereby allowing managersto make corrections. It also allows manag-ers to see, in the middle of a contract, whetherthey can meet the contract schedule if theycontinue working as they have been. An-other advantage of LOB is that it focusesattention on the production activities wherethere are problems, thereby facilitating ini-tiation of corrective action.

There are some limitations with the LOBtechnique. First, it is best suited for produc-tion and/or assembly-type processes thatare stable. The activities that make up theproduction plan must be definable and wellunderstood. Second, while this techniquepinpoints where a problem exists, it cannotidentify the specific problem.

4.3 SUMMARY

Each scheduling method has strengths andlimitations. Program Mangers must be fa-miliar with all of the techniques and choose

the method that allows them to meet theirgoals. The choice of schedule type dependson a number of factors, such as, the purposeof the schedule, its intended use, and thedecisions to be made from the informationpresented. For example, day-to-day man-agement of a project consisting of a numberof related and complex activities may re-quire a schedule that depicts the tasks, theirplanned duration, dependencies, progress,and resources allocated to each of them. If aPM must do detailed schedule analysis ofthis type of project, then the PM will mostlikely use a network schedule. This methodis the only way to use probability distribu-tions for time estimates rather than complet-ing an activity and project in a certain time.

On the other hand, the management of asingle activity may require a schedule thatreflects only the time planned for accom-plishing the task and the current status.Schedules showing only events, such as thecompletion dates of planned activities, orbar charts may be sufficient in those caseswhen the audience may not be concernedwith the details of the activities.

As a rule of thumb, Gantt and milestonecharts are useful to present information andsummarize program activities. They arealso usually the starting points for detailedplanning and creating a network schedule.Network schedules are usually created fordetailed planning and analyses. They arenecessary to determine the feasibility ofmeeting program goals, assessing risk, andconducting sensitivity analyses.

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1Quentin W. Fleming, John W. Bronn, and Gary C. Humphries, Project and Production Scheduling, Chicago,IL, Probus Publishing Co., 1987, p. 45.

ENDNOTES

5GANTT AND MILESTONE CHARTS

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Planned activity schedule

Status of activity

Forecasted completion behind schedule

Forecasted completion ahead of schedule

Symbol Meaning

Figure 5-1. Example Gantt Chart Symbols

5.1 DESCRIPTION

As discussed in Chapter 4, the Gantt chartis one of the oldest planning tools inexistence and is still used today at alllevels of project management. For ex-ample, PMs use Gantt charts to reportinformation concerning program activi-ties at milestone decision briefs, whileengineers may use them to manage thetasks associated with design activities.Because PMs often use Gantt and mile-stone charts to report information to re-view groups, they are treated jointly inthis chapter.

In its simplest form, a Gantt chart is aschedule that shows the start/stop datesof a program’s individual activities. Ituses symbols superimposed on a calen-dar to provide information about theoriginal plan, the status of the activity,and any forecasted changes to the plan.

There is no standard set of Gantt chart sym-bols. Planners should define them and con-sistently use them throughout the chart. Fig-ure 5-1 shows an example of the symbols thatcould be used in Gantt charts.

The schedule is displayed as a series ofhorizontal bars representing the duration ofactivities. A manager may show actualprogress against the schedule by shading ineach bar as activity progresses or may use acolored bar that is parallel to the schedulebar. Figure 5-2 shows a simple Gantt chartthat illustrates activities involved in devel-oping components of a weapons system.This type of display can be useful for convey-ing information about the program to thoseinvolved in its review or those charged withits day-to-day management.

From this example, we can see that as of lateMarch, the design, fabrication, and assemblyof the payload are ahead of schedule, [A].

Payload Design

Payload Fabrication

Payload Assembly

Test & Rework

Guidance & ControlDesign

Guidance & ControlFabrication

Guidance & ControlAssembly

Guidance & ControlTest & Rework

System Integration

System Test & Rework

Activity J F M A M J J A S O N D

[A]

[A] [B]

[A] [C]

[D] [E]

[E]

Figure 5-2. Example Gantt Chart

Based on this information, and an analysisof the activities, the PM has revised theplanned completion date for the payloadfabrication, [B]. In analyzing the currentstatus, the PM has determined that much ofthe work in payload assembly will have tobe done toward the end of the plannedactivity period. (In other words, the work isnot uniformly distributed throughout theperiod.) Thus, even though this activity isahead of schedule now, the PM has de-cided not to revise the planned completiondate for assembly and test, [C]. This Ganttchart also shows that development of the

guidance and control subsystem is not go-ing as well as planned. As of late-March,the fabrication is well behind schedule,[D]. After reviewing the progress and re-maining work, the PM has slipped theplanned completion dates for the fabrica-tion and assembly activities, [E]. They be-lieve that it is too early to revise the plannedcompletion dates for test and rework, andthe system integration and test activities.However, the slippage already experiencedshould serve as a warning that this entiredevelopment effort may be in trouble andwill require close monitoring.

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Now

While the Gantt chart focuses on activitiesand their duration, the milestone chart fo-cuses on planned significant events sched-uled to occur at specific times in the pro-gram. Such events could be the initiationor completion of a particularly importantor critical activity, equipment deliveries,reviews, or approval dates. Like the Ganttchart, the milestone chart uses symbolsimposed on a calendar to provide informa-tion about planned and actual completiondates and any revisions to the milestoneschedule. There is no standard set of sym-bols for milestone charts. Figure 5-3 showsthe symbols prescribed for reporting mile-stone information within the Air ForceMaterial Command. Different schedulingsoftware will often use unique symbols.

The important thing is that the symbols beclearly defined and consistently applied.

Figure 5-4 shows an example milestonechart for the program described in the Ganttchart in Figure 5-2. Note that events dis-played correspond to the beginning ofsome activities and the completion of all ofthem. Other events displayed representimportant occurrences and key decisionpoints within each of the activities, e.g.,preliminary and critical design reviews,“make or buy” decision, etc. In this ex-ample, we see that as of late-March pay-load design has progressed on schedule,[A], and that planned completion date forfabrication has been revised ahead of theoriginal schedule, [B]. As discussed in the

Figure 5-3. Example Milestone Chart Symbols

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Standard symbols have been adapted for Air Force milestoneschedules. The most common symbols used and their meanings areshown below.

Basic Symbol Meaning

Schedule Completion

Actual Comp