copyright © 1995-2004, dennis j. frailey, all rights reserved day 5, part 1, page 1 1/11/2004 day...

Copyright © 1995-2004, Dennis J. Frailey, All Rights Reserved Day 5, Part 1, 1/11/2004

Day 5, Part 1Basic Principles and Techniques

of Productivity, Quality and Cycle Time Management

Software Project Planning and Management

Dr. Dennis J. FraileyPrincipal Fellow

Raytheon Company


The Overall Planning Cycle

AnalyzeJob

Manage Risks

Execute

GenerateDetailed Plans

GenerateInitial Plans

Measure, Manage Productivity and Quality


Outline

• The basic principles of productivity

• Customer value and value-added analysis

• Principles of cycle time improvement


Basic Principles of Productivity


Productivity is ...

The quality or state of being productive

Webster’s 9th New Collegiate Dictionary

Productive:Having the power of producing;Yielding or furnishing results,

benefits, or profitsWebster’s 9th New Collegiate Dictionary


Productivity is NOT being ...

• Busy• Industrious• Virtuous

Productivity has to do with results (what and how much you produce), not with the means or

methods of production or the characteristics of the producer

Productivity has to do with results (what and how much you produce), not with the means or

methods of production or the characteristics of the producer

• Wealthy• Hardworking• etc.


Measuring Productivity

• Productivity is usually measured in terms of how much you produce in relation to how much you invest

Productivity = Output

Input or Investment


Productivity Measures• Products produced per labor hour• Return on investment• Bushels of grain per acre of land• Modules tested per week• Requirements validated per day

A farmer who invents a new method of growing that doubles the output per acre would be more

productive than a farmer who works longer hours and doubles output per acre.


Efficiency• Productivity is a measure of how

efficient your process is• Thus the way you improve

productivity is to make the process more efficient

• Many principles of quality engineering and cycle time improvement are directly related to productivity improvement

Copyright © 1995-2004, Dennis J. Frailey, All Rights ReservedDay 5, Part 1, 1/11/2004

Work in Process (WIP)

• WIP or “work in process” is work in the midst of being done– code being tested– specifications being written– objects being designed

• Excess WIP is work waiting to be done that is not being done -- waiting in queues instead– something is holding up the process


Excess “Work in Process” is a

Key Symptom

Excess WIP is a symptom of low productivity, long cycle time, and process

inefficiencyAnother key symptom is non-value-added

work. This will be addressed later.


Excess WIP Usually Implies a Constraint or Bottleneck

• When work is waiting to be done, it means that there is something holding it up

• Usually this is some kind of limitation on resources or other form of process constraint


Constraint Management


What Is a Constraint?•A constraint (bottleneck)

is any resource with capacity less than the demand placed upon it– This could be a person, a

computer, a network, a machine, etc.

•The constraint regulates the output rate of the entire process


•Improving a constraint provides capacity increase, often without capital investment

•Management provides flexibility to respond to changes in customer demand

•Reduces product cost as a result of increased output and improved efficiency

Why Is ConstraintManagement Important?

Hiking Boys Story


If 100 people each worked to increase

capacity by 1% on 100 different parts of

the software development process, the 1

person working on the constraint would

save the company thousands more than all

the other 99 people combined!

Where Are Your Resources Focused?


Effective Utilization

Before deciding to take actions

to improve the constraint, we

must first understand the

concept of effective utilization

Before deciding to take actions

to improve the constraint, we

must first understand the

concept of effective utilization


Effective UtilizationDefined

24 HOURS

AVAILABLE (A) UNAVAILABLE

REQUIRED (R)

Focus on decreasing ”R" and increasing “A”I.e., decrease effective utilization!

Focus on decreasing ”R" and increasing “A”I.e., decrease effective utilization!

= EFFECTIVE UTILIZATION =TIME REQUIRED

TIME AVAILABLERA


Effective Utilization-vs-

Productivity •Webster’s definitions:

– Utilize: To make use of– Busy: Constantly active or in motion– Productive: Yielding or furnishing

results, benefits or profits

We tend to measure utilization by how busy we are, BUT utilization tells us little about how productive we

are.

We tend to measure utilization by how busy we are, BUT utilization tells us little about how productive we

are.


Why Reduce EffectiveUtilization?

EFFECTIVE UTILIZATION

WIP

or

CY

CLE T

IME

100%

Running assets at a high effective utilization requires a costly cycle time trade off

per Erlang, 1917 (see Gross and Harris, pp 10-11, 101-102)


Examples

• Network performance vs load• Traffic flow vs load on freeway• Computer response vs load• Telephone dial tone delay vs

load• etc.


Utilizationvs Productivity

•High effective utilization will cause delays (cycle time) to increase greatly (increase investment) while output is increased only marginally, thus lowering productivity of the system

•Lower utilization means the resource is available when needed most, thus reducing delays and raising productivity of the overall system


Example - Firemen

• Why are firemen usually sitting around the fire station, essentially idle?

• Because they are needed ASAP when there is a fire.


Effective UtilizationAnd the Constraint

•Reducing effective utilization is especially critical at the constraint, because it determines the performance of the system as a whole

•To minimize effective utilization, we must make our assets more productive– This does not necessarily mean that

they are busier!


Ways to Improve Efficiencyat the Constraint

• Repair analysis improves our ability to repair and maintain the constraint, so we can improve its availability (increase “A”)

RepairmanStory


More Ways to Improve Efficiency

at the Constraint• Flow balancing allows us to effectively increase tool availability (increase “A”)– Flow variability to the constraint increases the

probability of the constraint running dry– Flow management helps control variability

• Statistical process control techniques can decrease required processing time as well as increase tool availability (decrease “R”, increase “A”)


Customer Value


What Constitutes Customer Value?

•Customer value is the real target of any competitive business

•The exact definition depends on the customer and the market–Sizzle vs steak–Features vs ease of use–Cost of operation vs comfort and safety


Defining Value

•Correctly defining value is the first step of customer satisfaction

•Cut out the tasks or features that do not directly or indirectly contribute to value–They add cost but do not provide

appropriate benefit


Dimensions of Customer Value• Low Costs / High Productivity

– Product development/manufacturing efficiency

– Attractive price

• High Quality– Customer satisfaction– Reliability & few defects

• Short Cycle Time– Rapid product development– Response to orders


The Goal

• Improve all components of the customer value triangle

CustomerValue

Quality

Prod

uctivityC

ycle

Tim

e


Without Process Change ...

• You can improve any one at the expense of the others

High Quality and

Low Cost, but Slow

High Quality,but Slow and Costly

Fast,Cheap,

butShoddy


EvenBetterValue

BetterValue

GoodValue

SatisfactoryValue

By Changing Process & Culture ...

… you can improve all together


Weinberg’s Definition of Quality

“Quality is value to someone”

• In Weinberg’s sense, value is quality• And the cost to produce value is the

cost of quality• But the term “cost of quality” is usually

used in a different context, to describe tasks we execute that improve quality

• Keep this in mind as we continue in this course


Value-Added Analysis


Who Produces Value?

•Value is the result of the best software engineers doing their best work.

•So software engineers produce value - and quality!


WHAT ARE THE COSTS OF SOFTWARE DEVELOPMENT?

Total Costs

Essential Non Essential

Value-Added Non-Value-Added


Value-Added Costs

Costs for tasks performed ...– Materials (e.g.., paper, software)– Labor hours (salaries)– Capital equipment (workstations,

facilities)

… that produce value– Products– Customer satisfaction– Future labor that will not be expended

• e.g.., reduced maintenance and repair


The Strict Definition of“Value-Added”

• Any activity that is part of the process is considered a value-added activity if it meets three criteria:

1) Must change the product in some way2) Must make the product more desirable to the customer (i.e., the customer wants the change)3) Must be done right the first time


The Strict Definition

• This very strict definition helps us open our minds

• So we identify the proper targets for process improvement.

• Anything that is not value-added is a suitable target for removal or improvement.


Things Not Part of Value-Added• Features the engineer thinks are nice but

the customer doesn’t care about• Moving a product around• Translating between incompatible tools• Repairing mistakes• Tests and inspections• Most management activities• Activities unrelated to the process• Many other things we tend to think of as

“necessary” or “desirable”– And some of them are necessary!


Some Non-Value-Added Activities

• Management• Quality Assurance• Testing• ...

The term “value-added” is used to help us improve our processes. It is not meant to

imply that the above tasks are not valuable or that the people who do them are

dispensable.

The term “value-added” is used to help us improve our processes. It is not meant to

imply that the above tasks are not valuable or that the people who do them are

dispensable.


Non-Value-Added Essential

• Costs for tasks performed because the process is not perfectly efficient– Peer reviews– Evaluations, inspections, verification and

validation– Metrics collection, storage and analysis– Extra reviews and verifications required

by customer or company policy (usually because of past problems)

– Certain overhead costs (benefits, support activities)


Why are they Essential?• They would not be necessary in a

perfect world• But they are necessary with our

current methods of product development and our current level of product development knowledge

Every process has some essential, non-value-added elements

Every process has some essential, non-value-added elements


Another Perspective

• Non-value-added but essential tasks are things we might wish we did not have to do

• But if we did not do them, things would be worse.

• However, we still can study them to find out how to minimize them, optimize them, and improve them


Non-Value-Added, Not Essential

• Tasks that are not value-added and that are not essential

• Typically, these are tasks that we perform because we have not really optimized our processes– For example, things we have always done

but no longer need to do – Or methods that once made sense but don’t

any more due to newer technologies or changes in the organization or environment


Examples of Non-Value-Added, Not Essential Tasks

– Excessive paperwork or approvals– Waits for test equipment or “signoff”– Debugging due to sloppy design or coding – Costs resulting from bugs in our software

development tools– Costs for activities unrelated to the process

These tasks should be eliminated or streamlined first, as they add cost for no

useful purpose

These tasks should be eliminated or streamlined first, as they add cost for no

useful purpose


Some Costs are Especially Painful

• High costs incurred later because of tasks not performed during software development (or not performed at the right time or in the right way)– Debugging– Correcting defects– Maintenance and repair

• These can subtract value:– Loss of customer good will– Future labor that must be expended


Typical Value-Added Categories

Non-EssentialEssential

Value-Added Non-Value-Added (costs $, no value to customer)1) Customer

Wants2) Changes

Product3) Done Right

the First Time• Design• Development• Fabrication• Documentation• Assembly• Process• Creation• Upgrade• Shipping

• Set-Up•Training• Planning• Customer-required test• Moving Data Between Steps• Many Quality Improvement activities

• Rework• Service• Modification• Expediting• Recall• Correction• Retest• Error Analysis

• Extra paperwork• Waits• Delays• Bottlenecks• Counting• Installing Software Tools• Extra Un-wanted Features


Analyzing Value-Added by Task or Category

This is the first step of value-added analysis• List all of the tasks or task categories in

your process• Then place each task into one or more of

the three value-added classes

Value-Added Essential Non-EssentialNon-Value-Added

• If a task fits more than one class, you may want to break it up into parts


Example Result of Analysis by Task / Category

Non-EssentialEssential

Value-Added Non-Value-Added (costs $, no value to customer)1) Customer

Wants2) Changes

Product3) Done Right

the First Time• Requirements analysis

• Design• Coding• Documentation• Integration• Manufacturing• Packaging• Shipping

• Estimating• Training• Planning• Customer-required acceptance test

• Configuration Control

• Inspections

• Debugging• Service calls• Warranty costs

• Fedex costs for patches

• Loss of customer goodwill

• etc.

• Approval by 7 people!

• Delays for test systems

• Data conversion between design tool and coding tool

• Wait for subcontracted hardware


Analyzing Value-Added Costs

• This is the second step of value-added analysis

• Each task can be assessed with respect to how much of its cost adds value

• Often, a task will contribute some value but have some non-value-added elements as well


Example of Cost Analysis

Task ValueAdded

NVAEssential

Non-Value-Added

Translate rqmts modelto UML f ormat

6

Evaluate Use Cases 24 4

Prepare structurediagrams

18

I nspect structurediagrams

8 2

Prepare report 2 2


What Are the Units?• The unit we measure for “cost”can

be anything that is available …– Dollars– Labor hours– Percent of time spent

• For initial analysis, the data do not have to be very accurate– Estimated percent of time spent– Estimated hours spent


Suggested Approach to Apply These Concepts in Practice

• Take a typical process from your work environment and do a value-added analysis by task or category

• For tasks that have some value-added and some non-value-added, estimate percentages of each

• Estimate what percent of the overall process is non-value-added

• Discuss how you might measure the costs (what units to use) using available information or information readily obtained


Typical Result

• Value-added -- 35% of total cost• NVA Essential -- 20% of total cost• NVA Non-essential -- 45% of total cost

– Top three items:• Rework due to design and coding errors --

14%• Extra customer support -- 12%• Labor for individuals waiting for test

equipment that is not available -- 11%


A Dilemma in Analyzing Non-Value-Added Costs

• Sometimes we must introduce non-value-added tasks to reduce the costs and impact of other non-value-added tasks

• This is a fundamental dilemma and a fundamental reason why we need to do more than analyze value-added

• We discussed this a little when we talked about cost of quality analysis


Note that Efficiency Improves Three Perspectives

Quality (Fewer Defects; Customer

satisfaction)

Low Cost or

High

ProductivityCustomer

Value

Shor

t Cyc

le T

ime

or

Sche

dule


Summary

• Understanding value is the starting point for effective and efficient processes

• Value-added analysis can help identify the best places to focus improvement efforts

• Just because something is “non-value-added” does not mean it is not worthwhile or necessary or good


References

• Knox, 1993, Raytheon studies reported by Houston and Keats, Software Quality Matters, vol 5, no 1 (Spring, 1997), U. of Texas SW Quality Institute

• Musa, John D, 1992, “The Operational Profile,” in Software Reliability Engineering: An overview.

• Weinberg, Gerald M., 1992, Quality Software Management, Volume 1, Systems Thinking, Dorset House, New York, ISBN 0-932633-22-6.


This Page Intentionally Blank


Principles of Cycle Time Improvement


Outline

• Why Cycle Time is Important• Symptoms and Causes of Cycle

Time Problems


Cycle Time Reduction

Time costs moneyCutting cycle time saves money and can

increase qualityThe issue: how to do it effectively

Quality (Fewer Defects; Customer satisfaction)

Low Cost or

High

Productivity

CustomerValueShor

t Cy

cle

Tim

e or

Sche

dule


Why Cycle Time is Important

Yes, Sir!Right Away,

Sir.

I Needthat Software

no later than next week! Why is it taking so long?

But we’re already working

overtime!

We’ll work overtime to get

it out, sir.


Importance of Low Development Cost for New Product

Development

0 5 10 15 20 25 30 35% LOSS OF TOTAL PROFIT

ON TIME, CORRECT PRODUCT COST, BUT WITH 50% DEVELOPMENT COST OVERRUN

Mckinsey & Co. Analysis of new product introduction profit and loss


Importance of Product Cost for New Product Development


ON TIME AND BUDGET, BUT PRODUCT COST 9% TOO HIGH



Importance of Cycle Time for New Product Development


ON TIME AND BUDGET, BUT PRODUCT COST 9% TOO HIGH

ON BUDGET, BUT PRODUCT IS SHIPPED 6 MONTHS LATE



Why Improve Software Development Cycle Time?

This does not necessarily mean that you will always need to develop

products quickly– Not all situations require short cycle

time– But for those that do, you are more

competitive

To improve the organization’s capability to develop software

products quickly.


What If You Don’t NeedShort Cycle Time?

• You can use this capability to:– Achieve competitive costs– Start software development later in

the program cycle– Allow less time to change

requirements– Get software development off of the

critical path


A Common Cycle Time Issue

It took so long to develop the software that the

customer’s needs changed. This resulted in excessive rework, higher costs, and further delays

It took so long to develop the software that the

customer’s needs changed. This resulted in excessive rework, higher costs, and further delays

The key is to develop the software quickly so today’s needs can

be met

We’ve changed

this requirement

.


How Can Cycle TimeBe Improved?

• The following video illustrates how to improve cycle time in an area that many of us are familiar with - building a house

• As you watch, think of ideas that might be applicable to software development


Some Lessons from the Cycle Time Video

• What did they do?

• Is there a software counterpart?

Things they did:

+_%$#@&

~~~~~~~~~~

~~~~~~~~~~~

~~~~~~~~~~~


How Is Cycle Time Improved?• Doing every process step faster?• Working longer hours?• Piling up work?

Faster!!!


Cycle Time Improvement Is ...

Improving the Process




Reducing the Critical Path





Eliminating Waits, Queues, Bottlenecks






Helping People work Smarter







Increased Cycles of Learning







Increased Cycles of Learning

Reengineering the Process


Symptoms and Causes ofCycle Time Problems


Symptoms ofCycle Time Problems

– Long waits and queues– Lots of “work in process”– High inventory levels– Excessive overtime

Tickets -->Tickets -->

How long isthis line?


Major Contributors toSlow Cycle Time

• Bottlenecks and constraints • Barriers• Inefficient processes• Inadequate training • Variability


Bottlenecks and Constraints

• Symptom: excess WIP or “work in process” – work waiting to be done that is not being

done -- waiting in queues instead– something is holding up the process

• Causes: limited capacity, poor processes, poor execution, or various barriers imposed by the organization

Places in the process that inhibit efficient flow of work


Example Process

Pizza OvenPizza Oven

ToppingsToppings

CrustCrust

BoxBox

SlicerSlicer

DeliverDeliver

Take OrderTake Order Where could

the bottlenecks

be?

Where could the

bottlenecks be?


Barriers

Things that prevent you from going faster, such as budgetary limits,

head count limits, lack of people or equipment, process problems, missing data, regulations, etc.


Sample Barriers

• Approval processes• Excessive paperwork• Limited space• Limited budgets• Wasteful processes• Defective information or

material• …..


Dealing with Barriers• Question why barriers are there

– Often they are the remnants of past problems and no longer need to be there• Obsolete approval procedures• Redundant checks and balances

– Sometimes the barriers have benefits but the organization does not understand their consequences • The “cure” may be more expensive than the problem


Organizations Often ResistRemoval of Barriers

• There are many reasons, such as …– Political factors– Power issues– How performance and success are

defined– Fear of change

Exercise

What barriers does your organization resist removing and why?


Lack of Training Contributesto Slow Cycle Time

• Inadequate Training - people do not know what to do, or how to do it most effectively– So it takes them longer to do the work

Investment in training usually pays off well

--But it requires foresight and faith


Process Contributesto Slow Cycle Time

• Inefficient Processes - processes containing steps that do NOT ADD VALUE– All processes have inefficiencies– Most processes can be improved in efficiency

• Variability - in processes, materials, skills, etc.– Variability is natural– But it can be controlled


Special Notice

• For the next exercise, each student should bring a pair of dice – Actually, one die per student will do

• And five coins or other tokens• And have some desk space free


References

• Deming, W. Edwards, Out of the Crisis, MIT Press, 1982.

• Goldratt, Eliyahu M. & Jeff Cox, The Goal, (North River Press, 1984.) Also, Theory of Constraints, It’s Not Luck, and Critical Chain Management.

• Swartz, James B., The Hunters and the Hunted, (Portland, Oregon, Productivity Press, 1994) ISBN 1-56327-043-9.


Outline

• Variability Experiment• Definitions, Terms and Concepts• Solutions to Cycle Time Problems

– Reducing Variability– Reducing Work in Process

• Observations and Caveats


Variability Experiment


Variability Experiment• Line up 5 tokens, like a train• Each turn, move tokens right

– See rules on a later slide

• How many turns does it take to move the leftmost token 15 positions?

Rules:– Round 1 will have low variability– Round 2 will have high variability– Round 3 will have high variability but higher

capacity


Token Setup for Experiment o o o o ... Round 1

o o o o … Round 2

o o o o … Round 3

^ ^ ^Left Token Right Token Positions to Move to

You may execute the rounds sequentially or in parallel.


Round 1 Rules• Each turn, move each token 3 places,

starting with the one on the right (3 places right, per turn)

• Result of first turn: o o o o o o

…

• Result of second turn: o o o o o o ...

How many turns does it take for the leftmost token to move 15 places to the right?


Round 2 Rules• Each turn, move each token n places,

starting with the one on the right, where n is a number from 1 to 5 determined randomly by rolling a die - 6’s don’t count.– Roll the die separately for each token– A token cannot move past another

• Note that the average move is 3 places• Possible result from first turno o o o o o …


Round 3 Rules• Each turn, move each token n places,

starting with the one on the right, where n is a number from 1 to 6 determined randomly by rolling a die - 6’s do count.– Roll the die separately for each token– A token cannot move past another

• Note that the average move is 3 1/2• Possible result from first turno o o o o o

…


Why Variability Results in Longer Cycle Time

• Slower tokens block faster ones• If you have a low roll on the die you

cannot take advantage of opportunities to “catch up”

• Even with higher average capacity (round 3), variability results in slower cycle time


Definitions, Terms andConcepts

The next few slides address some basic cycle time

terminology


Cycle Time is ...

• This could be:– First operation to ship– A single operation– A group of operations– Customer order to product delivery

• Cycle time includes actual processing time …… and all waiting time– Consider a “10 minute” oil change

The time required to execute all activities in a process


Lead Time is ...

• What is:– Your customer’s lead time?– Your potential customer’s lead time?

The maximum time the customer will wait between order placement

and product delivery.

How longwill ittake?

How longwill ittake?

Here’smy

order!


Cycle Time vs Lead Time• To be competitive, you must make:

• Otherwise, you lose business• Or else orders have to be started on

speculation, which means higher risk of rework or failing to satisfy the customer

Cycle Time < Lead Time


Throughput is ...

• This could be:– Modules tested per day– Components produced per week– Defects corrected per month– etc.

• Throughput is a measure of the output of a process

The number of products produced per unit of time


How to Measure Cycle Time?

Static Cycle TimeThe average of the actual cycle times (CT) experienced by some

number (n) of products

CT1 + CT2 + CT3 + CT4 +...+ CTn

nCycle Time =


Using This Measure• This can be used to measure cycle time

for many situations– For example, measure the cycle times of

the tokens in the variability experiment– Or measure the cycle times for cars being

serviced in a “10 minute oil change” station

• But this is not always easy to measure when many of the products are only partway through the process– So we need a dynamic measure


A Measure to Use when Static Cycle Time is Not Convenient

Dynamic Cycle TimeThe total work in process (WIP)

divided by the throughput of the process

Cycle Time =

WIP (products being developed)THROUGHPUT

This equation can be shown from queueing theory. See Gross and Harris, in reference list,

p83.


Revised Variability Experiment

• Take 5 turns for each round• Measure the total number of tokens that

reach the 15th position• After 5 turns, measure WIP• Also measure throughput, cycle time, etc

(see next slide)

Think of this as a 15 step process, with the tokens being work going through the

process


Solution Record forVariability Experiment

Round Total WI P StaticCT

DynamicCT

Through-put


This Page Intentionally Blank


Solutions to Cycle Time Problems


What Makes Cycle Time High?

• Inventory or work in process (WIP)• Higher overhead, longer delays• Process flow variability• Excessive waiting and long queues• Complexity of processes• Redundant and unnecessary steps

These are all related to each other


3 Steps to Cycle Time Improvement

• Reduce variability• Simplify the process• Reduce WIP

This order is recommended

Due to time limitations, we will only address the first and third of these in this module.

Process simplification will be addressed in the next module


Reducing Variability


Variability Increases Cycle Time

USLLSLLSL USLUSLLSLUSLLSL

21 3 4

If price and delivery were equal, which supplier would

you buy a product from?

OUTPUT FROM FOUR DIFFERENTPROGRAMMING SHOPS


Sources of Variability• Movement of programs or documents

between workstations or systems• Machines or software not being available• Hot lots / priority tasks that disrupt normal

activity• Software defects that require rework and

debugging• Special cases that require holds and delays• Inconsistent processes and procedures• Excessive approval requirements• Hundreds more...


Expediting via Priority Tasks•The tendency is to establish many

levels of priorities– Hot– Super hot– Immediate– Per the boss

•Pressure exists to raise the number of priority tasks

•The list always grows


Other Problems Resulting from Priority Tasks

• Managing priorities consumes many resources

• And it delays other jobs


Expediting vs Cycle Time

0 5 10 15 20 25 30 35 40 45 50 55 60 65 70

Percent expeditedCycle

Tim

e M

ult

iplier

for

Non

-Exp

ed

ited

Jo

bs

Cycle

Tim

e M

ult

iplier

for

Non

-Exp

ed

ited

Jo

bs

• When we expedite a product, other products are delayed

• In some cases, each product waits until it is expedited before it moves at all


Variability Management MustMinimize Expediting

7 14 21 28

BAU

NUMBEROF

SHIPMENTS

CYCLE TIME (DAYS)

7 14 21 28CYCLE TIME (DAYS)

NUMBEROF

SHIPMENTS

EXPEDITEDLOTS DELINQUENT

LOTS

With managed priorities, you improve the normal case and reduce the need for

“priority jobs”


A Strategy for Managing Priorities

• Allow only two priorities

– Hot– Not hot

• Control the maximum percentage of “hot” (less than 8% to 10%)– If you add a hot job, you must subtract

another

– This requires discipline (and faith that it works!)


Further Management of Priorities

• Monitor distribution throughout the process– Do not plug up one operation or

individual with priority tasks

• Monitor frequently

• Remove tasks from the priority list when they don’t really need priority



Cycle Time, Utilizationand Variability

WIP

or

CY

CLE T

IME

100%


Higher Utilization IncreasesCycle Time


WIP

or

CY

CLE T

IME

100%

SOME VARIABILITY



Variability Affects theExtent of the Added Delay

WIP

or

CY

CLE T

IME

100%

NO VARIABILITY

SOME VARIABILITY


EFFECTIVE UTILIZATION OR THROUGHPUT

High Low

Variability

Output

OpportunityCycle TimeOpportunity

Variability ReductionOpportunities

WIP

or

CY

CLE T

IME


ReducingWork in Process (WIP)


High WIP = High Cycle Time•Any intermediate work in the

system is WIP.•Anything that is not being actively

processed is excessive WIP.

For related background, see Gross and Harris, in reference list, p83.

Dynamic Cycle Time = WIP

THROUGHPUT


Examples of Excessive WIP for Software

•Code waiting to be tested•Designs waiting to be coded•Specifications waiting to be inspected•Change requests waiting for approval•Hundreds more...


Smooth Flow - Ideal Process

• The ideal process flows smoothly, like a train running on tracks.

Note: tracks are empty most of the time


Uneven Flow - Typical Process

• Lots of exits and entrances

• Vehicles of varying sizes and speeds

Note: streets are usually crowded - with WIP!

• The typical process runs unevenly, like vehicles on a city street

» Some drivers uncertain of what they want to do

» Lots of stoplights to “control” the flow (mainly to prevent collisions)


Techniques for ObtainingSmoother Flow

• Identify bottlenecks and constraints -- and manage/optimize them

• Utilize pull systems instead of push systems

• “Conduct the orchestra” (keep everyone going at the same speed)

• Flow management systems• .....


Observations and Caveats


Too Much Measurement!• The tendency is to measure too

much and in too much detail– Rough estimates usually identify the

biggest problems and opportunities


Some of The Problems &

Solutions are Technical• 30% of the improvement comes from

technical changes– Process changes– Tool changes– Changing rules and operations


Most of The Problems &

Solutions are Not Technical• 70% of the improvement comes from

organizational and people changes, such as– Education– Communication– Management– Teamwork


• Practitioners generally focus on their work and on what they THINK is happening rather than on what IS happening– They tend not to see all of the waits, queues,

etc. that they cause themselves– Their perception of how they spend their time

is generally incorrect– They are too busy getting the job done to see

how they might improve it

Independent Observers See Problems and Opportunities the

Best


• Just as athletes rely on coaches, software engineers need to learn to trust in others to observe and help them do better

The Athletic Coach Analogy


Software Developers areAccustomed to

Improving Cycle Time

•Think of your software development process as a large computer program that runs too slow. – How would you make it run faster?– Imagine how you would speed up a

computer program . . . . . . . .– Then draw analogies to the software

development process


Improve the Process the way you would Speed Up a

Program

Code Speed-up• Faster hardware• Better algorithm• Optimizing compiler• Remove code from

inner loops• Optimize code• …..

Process Speed-up• Faster hardware• Better process• Eliminate waste• Remove redundant

steps• Eliminate wasteful

meetings and approvals

• …..


You don’t pay for the steps you don’t do– Fewer steps means fewer opportunities to

introduce defects– Shorter cycles means less time to change

requirements– Shorter cycles means more time to iterate

designs or benefit from cycles of learning

Cycle Time Bonus It generally turns out that

improved cycle time produces lower costs and higher quality as

well!


Examples ofSoftware Cycle Time

Techniques• “Just-in-time” training• Plan testing and test equipment well in advance• Rethink the detailed design process

– Do you need to maintain detailed design documentation?

– Do you need to do detailed design at all? • Use on-line requirements and design models

instead of paper documents and specifications


Examples of Commonly FoundSoftware Cycle Time Barriers

• Poor communication/cooperation between software development and the rest of the organization

• Poor management of unstable requirements, algorithms and interfaces

• Contention for test assets -- need better planning, assets allocated to software test

• Poorly qualified software subcontractors


More Commonly FoundSoftware Cycle Time Barriers

• Excessive paperwork, signatures, and reporting– Negotiate reductions with

management and customer

• Reuse of software not designed for reuse

• Attempts to use the latest tools and methods -- without adequate support and integration


Summary• Measure cycle time• Measure rework• Use these to show the value of process

improvements• And to convince others that your

techniques are worthwhile– Because many cycle time improvement

techniques are “counterintuitive”

Focussing on cycle time can make the whole process more efficient, and effective


References

• Deming, W. Edwards, Out of the Crisis, MIT Press, 1982.

• Goldratt, Eliyahu M. & Jeff Cox, The Goal, (North River Press, 1984.) Also, Theory of Constraints, It’s Not Luck, and Critical Chain Management.

• Gross and Harris, Fundamentals of Queueing Theory (Wiley).

• Swartz, James B., The Hunters and the Hunted, (Portland, Oregon, Productivity Press, 1994) ISBN 1-56327-043-9.

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