Copyright © 1995-2003, Dennis J. Frailey, All Rights Reserved Day 1, Part 4, Page 1 4/19/2003 4) The Work Breakdown Structure (WBS)

Copyright © 1995-2003, Dennis J. Frailey, All Rights Reserved Day 1, Part 4, Page 14/19/2003

4) The Work Breakdown Structure

(WBS)


Outline• Introduction

– Purposes, Benefits and Examples of a WBS

– Additional WBS Terminology• Risks in preparing a WBS• Summary• Appendix -- Constructing a WBS

– Steps of Construction– Notes on WBS– Examples of Issues in preparing WBS


The Overall Planning Cycle

AnalyzeJob

Manage Risks

Execute

GenerateDetailed Plans

GenerateInitial Plans

Measure, Manage Productivity and Quality


Detailed Planning - Processes

EstimateSize

EstimateEffort and

Cost

EstimateSchedule

Evaluate

Source InformationStatement of Work

RequirementsConstraintsStandardsProcesses

Historyetc.

WBS Size

Effort &Cost

Schedule

OKCompleteDetailedPlanning

Revise &Negotiate

Not OK


Detailed Planning - Questions

How BigIs It?

How MuchWill itCost?

How Long?What Do WeDo When?

Is ThisAcceptable?

What Do WeHave To

Do?

WBS Size

Effort &Cost

Schedule

OKCompleteDetailedPlanning

What CanWe Change? Not OK


Work Breakdown Structure Introduction

Just tell me what I have to

do!


The Work Breakdown Structure Is ...

• A hierarchical list of the activities required to complete a project

• It includes tasks for – Software development– Software development management– Support of software development– Any other activities required to meet

customer requirements, such as training, documentation etc.

ParserCode

GeneratorFile

SystemRun TimeSystem

UserInterface

ManageSoftware

Development

Build “C”Compiler

Build TestSuite

WriteDocumentation

WriteInstallationSoftware

Software for“C” Compiler


The Work Breakdown Structure Is ...

• The first step of Detailed Planning• It forms the fundamental basis for

– Size Estimate– Effort Estimate– Cost Estimate– Schedule Estimate– Other detailed planning tasks


Why Use a WBS?

• To document all work that must be done to develop & deliver the software in a satisfactory manner

WBSWBS

Copyright © 1995-2003, Dennis J. Frailey, All Rights ReservedDay 1, Part 4, Page 104/19/2003

Is This Necessary?

• A WBS is redundant with various “source” documents (SOW, requirements document, etc.)

• But the WBS serves to consolidate information from many sources into one place and into an organized format.

A “table of contents” for the project.

A “table of contents” for the project.


Top Level Role of WBS

HistoricalRecords(at end

of project)

CostEstimate

(proposal &/project start)

CostTracking(during

execution)

WBS

SourceDocuments

(SOW, Requirements,

contract, test criteria,

etc,)


An example of a WBSShown as a Tree

ParserCode

GeneratorFile

SystemRun TimeSystem

UserInterface

ManageSoftware

Development

Build “C”Compiler

Build TestSuite

WriteDocumentation

WriteInstallationSoftware

Software for“C” Compiler


An example of a WBSShown as Indented Text

1 Software for “C” Compiler 1.1 Build a “C” Compiler

1.1.1 Build a User Interface 1.1.2 Build a File System 1.1.3 Build a Parser 1.1.4 Build a Code Generator 1.1.5 Build a Run Time System

1.2 Build the Test Suite for the Compiler

1.2.1 etc.

1.3 Write Documentation 1.4 Write Installation Software

1.5 Manage Software Development


1.n The compiler project1.n.1 - The basic parts of the compiler

1.n.1.1 - the steps of the development process

1.1 Build a “C” Compiler1.1.1 Build a User Interface

1.1.1.1 Analyze Requirements for User I/F

1.1.1.2 Design the User Interface 1.1.1.3 Code the User Interface 1.1.1.4 Test and Integrate the User

Interface

1.1.2 etc.

Example of an Additional Level of Detail in a WBS


1.1.n - The steps of the development process 1.1.1.n - the basic parts of the compiler

1.1 Build a “C” Compiler 1.1.1 Analyze Requirements

1.1.1.1 User I/F

1.1.1.2 File System 1.1.1.3 Parser 1.1.1.4 Code Generator 1.1.1.5 Run Time System

1.1.2 Design

1.1.2.1 etc.

Alternative Example


Purposes of a WBS

• To organize the work to be done• To illustrate the work to be done• To assure that all necessary work

has been identified• To divide the work into small, well

defined tasks


Why Do a WBS?

• To facilitate planning, estimating and scheduling of the project

• To identify contractual tasks and deliverables

• To provide a basis for data monitoring and historical data collection


Using a WBS for Estimating

• To make sure that all tasks are estimated

• To make sure that each element of the estimate corresponds to a necessary task

• To “roll up” costs of individual elements to get total costs for sub-elements or for the system as a whole


“Rolling Up” Costs

$15K $38K$13K $24K$22K

$31K$112K $85K $28K $45K

$301K


Using a WBS for Project Tracking and Oversight

• Cost Accounting– Work can be assigned and “charged” based

on specific WBS elements– You can then determine the actual cost of

each element

• Schedule Performance– You can monitor which tasks are done– And estimate how much is left to be done


Additional WBS Terminology


Additional WBS Terminology

Activity

Work Package

Basis of Estimate

WBS Dictionary

DO X

DO Y

DO Z

DO Q

STORAGE


The Activity

• A specific task to be performed.• Occurs at all levels of the WBS.

Activities

DO X

DO Y

DO Z

DO Q

STORAGE


Characteristics of an Activity

• Generally, each activity corresponds to some documented work requirement, such as a SOW paragraph or customer work order.

• Some activities are merely implied– Management, Acquisition of resources,

Details of development process etc.


Work Package

The Work Package

• It is a bottom-level or “atomic” activity in the WBS

• Represents a task or group of tasks whose costs will be tracked and estimated together


Typical Work Package Characteristics

• Associated with a concrete event or milestone

• Suitable for independent cost estimating and tracking

• Small enough to manage and large enough to be worth tracking separately

• Suitable for allocating part of the budget – people, hours, dollars, computers, etc.


Examples of Work Packages

CodeCompiler

Test theCompiler

DesignCompiler

Write HelpFiles forCompiler

LeadCompiler

Effort

Travel forCustomerMeetings

CompilerDevelopment

ConfigurationManagementfor Compiler

QualityAssurance

for Compiler

SoftwareDevelopment


Guidelines for Selecting aWork Package

• Start with the process – Consider associating each work package

with a discrete portion of the process

• Examine the design (high level)– Consider associating each work package

with a discrete portion of the software, such as a software item or a major component of a software item


Guidelines for Selecting aWork Package

(continued)

• Categorize the nature of the work or cost or payment– Consider associating a work package

with a given type of work or payment– For example, separate work packages

for:• travel• equipment• development labor


Basis of Estimate

Item: Travel for Customer Interchange Meetings

WBS #: 1.5.2.3 Cost: $16,800

Description: Four trips to customer for I/C meetings. Each trip will involve 3 engineers and be 2 days long

Cost Calculation: 4 * 3 * 2 * $700/day = $16,800

Basis of Estimate• A description of a work package

and a rationale for its cost estimate


WBS Dictionary

• A supplement to the WBS that provides additional detail for each WBS activity

• Typical contents for a given activity:– Inputs, Outputs, Performance Goals &

Reviews– Exit or Completion criteria– Sub-activities that make up this activity– Detailed description (if a work package)

• Other contents are derived from the process


Sample WBS Dictionary for a Work Package

Code theFile

System1.1.3.3

Integratethe

File System1.1.3.4

Design theFile

System1.1.3.2

AnalyzeFile System

Requirements1.1.3.1

Write HelpFiles1.1.5

ManageDevelopment

1.1.1

Build TestSuite1.1.2

Develop theFile System

1.1.3

WriteInstallation SW

1.1.4

Develop a“C” Compiler

1.1


Example WBS Dictionary for a work package

Name: Design the File system (for compiler)

WBS #: 1.1.3.2 Performance Goal: 3 months

Inputs: Requirements Specification for the file system

Output: File system design descriptionReviews: Preliminary design review, detailed

design review and intermediate peer reviews

Exit Criteria: File system design addresses all requirements and meets design

standardsDetailed Description:

Using the Booch method, use object oriented design technique to establish a design for the file system.


Sample WBS Dictionary for a Higher Level Activity

Code theFile

System1.1.3.3

Integratethe

File System1.1.3.4

Design theFile

System1.1.3.2

AnalyzeFile System

Requirements1.1.3.1

Write HelpFiles1.1.5

ManageDevelopment

1.1.1

Build TestSuite1.1.2

Develop theFile System

1.1.3

WriteInstallation SW

1.1.4

Develop a“C” Compiler

1.1


Example WBS Dictionary for a higher level activity

Name: Develop File system (for compiler)WBS #:1.1.3 Performance Goal: 8 month

scheduleInputs: Requirements specs for file systemOutput: File system codeReviews:Preliminary design review, detailed design

review, test status review, formal qualification test, internal peer reviews

Exit Criteria: File system passes functional tests based on requirements

Subtasks: Requirements analysis (1.1.3.1); design (1.1.3.2);

code (1.1.3.3); integrate (1.1.3.4)


Goals of a Good WBS (1)

1) Specify the ingredients of the project clearly and concisely

2) Identify the responsibilities of each task and its place within the whole

3) Identify project performance targets at every level

(1) Maciariello, Joseph A., “Making program management work,” Tutorial on Software Management, IEEE Computer Society Press, 1986, p. 93.


Goals of a Good WBS (continued)

4) Support the comparison of actual performance with target values

5) Motivate people to meet targets


Observations on the WBS

• Different parts of the WBS could have different levels of detail

• Later updates of the WBS could provide more detail than what is developed initially


Observations on the WBS (continued)

• Avoid making too many very small work packages– If several of them have nearly

identical descriptions, see if you can combine them.

– Each level in the WBS multiplies by 5-10 the amount of detail that must be estimated, tracked, etc.)

• Trace the WBS to the requirements


Risks in Preparing a WBS


Risks - I

Too Much Detail

• Increases overhead of monitoring and estimation

• Customers or managers might insist on tracking based on the WBS

• You may have two WBSs to get around this: a “formal” WBS at the high level and a “working” WBS at the detail level


Risks - II

Work Packages are Vague

• Look for concrete starting & ending events with specific evaluation criteria

• A work package should be discrete, trackable, & measurable


Risks - III

Excluding certain tasks

• Make sure everything is covered – It is easy to assume someone else

covered it

• If you don’t know, ask• Exclusion implies 0 cost, which is

rarely true if you must do the task


Risks -IV

Duplication of activities

• It is easy to have the same work show up in more than one place, especially on a large project

• Managers must “scrub” the WBS


Risk Mitigation Approaches

• WBS inspection or walkthrough– Look for completeness, consistency, well

defined activities, etc.– Let others see the WBS (you tend to have

tunnel vision and may miss something)

• Trace to source documents (and, later, to cost estimate)

• Remember that the WBS is part of the plan– Include WBS revisions in re-planning

activities


SummaryWork Breakdown Structure

• WBS is a document that organizes information from other sources in order to facilitate– Planning of the project – Progress tracking– Historical records of the project


Summary Work Breakdown Structure

• It should be developed such that it – Is compliant to any

organizational/project standards– Is detailed enough to be useful for

tracking and small enough to be manageable

– Includes the costs of activities that are not realized otherwise, for example, requirements change etc.


References Work Breakdown Structure

1. Maciariello, Joseph A., “Making program management work,” Tutorial on Software Management, IEEE Computer Society Press.

2. Tausworthe, Robert C., “The Work Breakdown structure in Software Project Management”, Proceedings of the Second Software Lifecycle Management Workshop


AppendixConstructing a Work Breakdown Structure


Steps for Constructing a WBS1. The software hunt - identify SW tasks2. Place software within the project WBS3. Determine the architecture of the

software portion(s) of the WBS4. Populate the chosen WBS structure

with tasks from source documents5. Develop WBS to source documents

trace matrix 6. Determine the cost category for each

activity


1. The Software HuntGo through the source documents and make a complete list of all items that impact the cost of doing the software

Document Paragraph Description

SOW 1.3.4 Design Software for Compiler

SOW 2.3.3 Travel for Design Reviews

...

Contract 7.13.2.a Follow ISO Standard 5432f

Rqmts. Doc. 3.4 Use data compression

...

Customer Meeting on 3/5/95 Code all software in C++


The Software Hunt

• SOW - usually the best item to start with• Specifications• Concept of Operation documents• Requirements Documents of Many Kinds• Design Documents• Standards (internal and external)• Customer Conversations• Test Criteria or Expectations

The Source Documents


2. Place Software in the Context of a Larger WBS

• Many organizations have a standard WBS architecture for projects

• If not, then determine what project requirements may be applicable– For example, your project manager

may have a specific approach -- number of levels, where to show certain kinds of costs, etc.


Example: SoftwareEmbedded in Hardware

Radar

Sig. Proc. Antenna Power S. Cabinet

Computer SoftwareAnalog

This approach can result in a large number of software elements in the WBS. A spreadsheet

may be handy for tracking them all.

This approach can result in a large number of software elements in the WBS. A spreadsheet

may be handy for tracking them all.


Example: SoftwareIndependent of Hardware

This approach may tend to isolate software planning from the rest of the system, resulting in inconsistent interpretations of requirements, etc.

This approach may tend to isolate software planning from the rest of the system, resulting in inconsistent interpretations of requirements, etc.

System

Software Electrical Mechanical Management

Editor etc.Compiler


3. Determine the Architecture of the Software WBS

• Many organizations have standard software WBS architectures to help keep track of costs consistently across the organization

• Different software products (configuration items) may need different WBS structures

continued…


Some “Standard” Architectures

for a Software WBSSoftware

WordProc.

Database

Spreadsheet

UserI/f

EditorFor-

matter

Rqmts Design Code Test

Software

WordProc.

Database

Spreadsheet

UserI/f

EditorFor-

matter

Rqmts Design Code Test


Example WBS Architectures

All Software

Products

Components

Process Steps

All Software

Process Steps

Products

Components

All Software

Organizations

Products

. . .

All Software

Products

Organizations

. . .


4. Populate the WBS• Assign each activity identified in

step 1 to an appropriate place in the work breakdown structure

SOW 1.1.1 Develop C Compiler 1.0 Software for “C” CompilerSPEC 2.0 Develop Compiler 1.1 Build a “C” CompilerSPEC 2.1 User I/F for PC 1.1.1 Build a User InterfacePROC STD 3.4 Requirements Analysis 1.1.1.1 RA for User I/FPROC STD 3.5 Design 1.1.1.2 Design for User

I/F ..... ..... .....SPEC 2.2 File System 1.1.2 Build a File System .... .... ....SPEC 3.0 Test IAW Company Stds 1.2 Build the Test Suite .... .... ....SOW 2.3.4 Provide User Guide 1.3 Write Documentation .... .... ....


Document Parag WBS# Description

SOW 1.3.4 1.1.2.2 Design Software for Compiler

SOW 2.3.3 1.7.1 Travel for Design Reviews

RequirementsSpecifications 3.1.1 1.1.2.4 Perform Quality Audit

5. Construct a Trace Matrix from the WBS to the Source Documents• Add a WBS activity number column

to the matrix constructed in step 1.


Additional (Optional) Information in WBS Trace

• Who is responsible for estimating cost• Who is responsible for development• What paragraph of the software

development plan addresses this task• What standards are to be applied in

performing this task• What is the final cost estimate for this

WBS item – Often filled in after estimating cost


Using the WBS Trace Matrix1) Sort by source document &

paragraph and make sure each task is covered in the WBS

2) Sort by WBS number and make sure each corresponds to a legitimate activity that must be performed

3) Sort by WBS and requirements document to identify all the requirements that must be met by each activity (helps in cost estimating)


Use of the Trace Matrix During Project Execution

• When requirements are changed, you can determine which activities are potentially affected

• When activities encounter problems, you can determine which requirements or contract stipulations may need to be renegotiated


Doc Parag WBS# DescriptionSOW 1.3.4 1.1.2.2 Design Software for Compiler

SOW 1.3.4 1.1.3.2 Design Software for Editor

SOW 2.3.4 1.1.3.2 Use Booch Design Method

SOW 2.3.3 1.7.1 Travel for Design Reviews

Suppose SOW 1.3.4 says "design software"and SOW 2.3.4 says "use Booch design method"

Redundancy OK in the Trace Matrix


Document Parag WBS# Description Category

SOW 1.3.4 1.1.2.2 Design Software for Compiler

S

. . . . . . . . . . . .

SOW 2.3.3 1.7.1 Travel for Design Reviews C

. . . Continued...

6. Determine Cost Categories• Determine the cost category for each

element in the matrix (from step 1 or step 5) or the WBS (Step 4)


Possible Cost CategoriesCode Category Affects Examples

S SoftwareDevelopment

Cost&Schedule

Software Design, SoftwareCoding, Software Testing

SA AdditionalSoftware

Effort

Cost&Schedule

Software Requirements,System Testing

P SoftwareSupport

Cost Software Management, SQA,Configuration Management

AL AdditionalLabor

Cost Special Audits,Document Generation

AD AdditionalDollars

Cost Travel, Development Tools,Special Equipment,