Technical debt is slowing your software development projects. Any developer who has gone beyond version 1 has encountered it. Technical debt takes different forms, has many different origins, and does not always equate to bad code quality. Much of it is incurred due to the passage of time and a rapidly evolving business environment. Some is in the form of hundreds of little cuts; some is massive and overwhelming, the result of a single poor design choice. Philippe Kruchten explains how to distinguish different types of technical debt, identify their root causes, objectively assess their impact, and develop strategies suitable in your context to limit or selectively reduce the technical debt you incur. Discover what debt you can happily live with. See when to declare bankruptcy. And learn that not all technical debt is bad. Just like in the real world, some technical debt can be a valuable investment for the future.

1. !
!
T1#
Session!
6/25/2015! !
10:15!AM!
!
!
!
!
“Managing#Technical#Debt”##
Presented#by:#
Philippe#Kruchten#
Kruchten#Engineering#Services,#Ltd.#
#
#
#
#
#
Brought#to#you#by:#
#
#
#
#
#
#
340!Corporate!Way,!Suite!300,!Orange!Park,!FL!32073!
888D268D8770!E!904D278D0524!E!sqeinfo@sqe.com!E!www.sqe.com!
!
!
!

2. !
!
!!!!! !
!!!!
Philippe Kruchten is professor of software engineering at the University of British Columbia,
in Vancouver, Canada, where he holds an NSERC chair in design engineering. He joined UBC
in 2004 after a thirty-year career in industry, where he worked mostly with large software-
intensive systems design in the domains of telecommunication, defense, aerospace, and
transportation. Philippe’s current research interests are in software architecture (in particular,
architectural decisions and the decision-making process), the evolution of large software and
technical debt, and agile software development practices. He is the founder of Agile
Vancouver.
Philippe Kruchten
Kruchten Engineering Services, Ltd.

3. Managing&Technical&Debt& February&2015&
Copyright&©&2015&by&Philippe&Kruchten& 1&
Managing&Technical&Debt&
&
Philippe&Kruchten&&
&
June&25,&2015&
@&StarCanada&
&
&
Philippe&Kruchten,&Ph.D.,&P.Eng.,&CSDP&
Professor'of'So)ware'Engineering'
NSERC'Chair'in'Design'Engineering'
Department&of&Electrical&and&Computer&Engineering&
University&of&BriJsh&Columbia&
Vancouver,&BC&Canada&
pbk@ece.ubc.ca&&&&&
&& &&
Founder'and'president&
Kruchten&Engineering&Services&Ltd&
Vancouver,&BC&Canada &&
philippe@kruchten.com&&&&&&&&@pbpk&
&
Copyright&©&KESL&2015& 2

4. Managing&Technical&Debt& February&2015&
Copyright&©&2015&by&Philippe&Kruchten& 2&
Outline&
• What&is&technical&debt?&&
• The&technical&debt&landscape&
• Limits&of&the&metaphor&
• Managing&technical&debt&
• Tools&and&techniques&
• Research&on&technical&debt&
June&25,&2015& Copyright&©&KESL&2015& 3&
Technical&Debt&
• Concept&introduced&by&Ward&Cunningham&
• OTen&menJoned,&rarely&studied&
• All&experienced&soTware&developers&“feel”&it.&
• Drags&longZlived&projects&and&products&down&
June&25,&2015& Copyright&©&KESL&2015& 4&

5. Managing&Technical&Debt& February&2015&
Copyright&©&2015&by&Philippe&Kruchten& 3&
Origin&of&the&metaphor&
• Ward&Cunningham,&at&OOPSLA&1992&
&“Shipping&first&Jme&code&is&like&going&
into&debt.&A&li_le&debt&speeds&development&&
so&long&as&it&is&paid&back&promptly&with&a&&
rewrite…&
The&danger&occurs&when&the&debt&is&not&&
repaid.&Every&minute&spent&on&notZquiteZright&code&
counts&as&interest&on&that&debt.&EnJre&engineering&
organizaJons&can&be&brought&to&a&standZsJll&under&the&
debt&load&of&an&unconsolidated&implementaJon,&
objectZoriented&or&otherwise.”&
Cunningham,*OOPSLA*1992*
June&25,&2015& Copyright&©&KESL&2015& 5&
Technical&Debt&(S.&McConnell)&
• Implemented&features&(visible&and&&
invisible)&=&assets&=&nonZdebt&
• Type&1:&unintenJonal,&nonZstrategic;&&
poor&design&decisions,&poor&coding&
• Type&2:&intenJonal&and&strategic:&&
opJmize&for&the&present,&not&for&the&&
future.&
– 2.A&shortZterm:&paid&off&quickly&(refactorings,&etc.)&
• Large&chunks:&easy&to&track&
• Many&small&bits:&cannot&track&
– 2.B&longZterm&
McConnell*2007*
June&25,&2015& Copyright&©&KESL&2015& 6&

6. Managing&Technical&Debt& February&2015&
Copyright&©&2015&by&Philippe&Kruchten& 4&
Technical&Debt&(M.&&Fowler)&
Fowler*2009,*2010*
June&25,&2015& Copyright&©&KESL&2015& 7&
First&more&capabiliJes&
First&more&infrastructure&
Then,&more&infrastructure&
Then,&more&capabiliJes&
underesJmated&&
reZarchitecJng&costs&
neglected&cost&of&delay&
to&market&
need&to&monitor&technical&
debt&to&gain&insight&into&
lifeZcycle&efficiency&
Example&
Ozkaya,&SEI,2010&June&25,&2015& Copyright&©&KESL&2015& 8&

7. Managing&Technical&Debt& February&2015&
Copyright&©&2015&by&Philippe&Kruchten& 5&
Technical&Debt&(S.&McConnell)&
• TD:&A&design&or&construcJon&
approach&that&is&expedient&in&the&
short&term&but&that&creates&a&
technical&context&in&which&the&
same&work&will&cost&more&to&do&
later&than&it&would&cost&to&do&now&
McConnell*2011*
June&25,&2015& Copyright&©&KESL&2015& 9&
Time&is&Money&(I.&Gat)&
• Convert&this&in&monetary&terms:&&
&“Think&of&the&amount&of&money&the&&
borrowed&Jme&represents&–&the&&
grand&total&required&to&eliminate&&
all&issues&found&in&the&code”&
Gat*2010*
June&25,&2015& Copyright&©&KESL&2015& 10&

8. Managing&Technical&Debt& February&2015&
Copyright&©&2015&by&Philippe&Kruchten& 6&
Example:&TD&is&the&sum&of…&
• Code&smells & &167&person&days&
• Missing&tests & &298&person&days&
• Design & & & &670&&person&days&
• DocumentaJon &&&67&person&days&&
&
Totals'
&Work& & & & &1,202&person&x&days&
&Cost & & & & &$577,000&
June&25,&2015& Copyright&©&KESL&2015& 11&
Israel&Gat,&2010&
h_p://theagileexecuJve.com/2010/09/20/howZtoZbreakZtheZviciousZcycleZofZtechnicalZdebt/&
(more)&
Relentless&
Pressure&
Take&
Technical&
Debt&
Fail&to&Pay&
back&
Technical&
debt&
Technical&
Debt&Accrues&
Reduced&
Development&
Team&
Velocity&
June&25,&2015& Copyright&©&KESL&2015& 12&

9. Managing&Technical&Debt& February&2015&
Copyright&©&2015&by&Philippe&Kruchten& 7&
Tech&Debt&(Jim&Highsmith)&
Source:*Highsmith,*2009*June&25,&2015& Copyright&©&KESL&2015& 13&
Value,&Quality,&Constraints&
• Value&=&extrinsic&quality&
– Metric:&Net&present&
value&
• Quality&=&intrinsic&
quality&
– Metric:&Technical&debt&
• Constraints&=&cost,&
schedule,&scope&
– Metric:&Cost&
Value&
Quality&
&&&
Cost&
&Highsmith*2010&
June&25,&2015& Copyright&©&KESL&2015& 14&

10. Managing&Technical&Debt& February&2015&
Copyright&©&2015&by&Philippe&Kruchten& 8&
State&of&affairs&
• Opinions,&posturing,&proclamaJons&
• Li_le&objecJve&facts&
“...there&is&a&plethora&of&a_enJonZgrabbing&
pronouncements&in&cyberspace&that&have&not&
been&evaluated&before&they&were&published,&
oTen&reflecJng&the&authors’&guesses&and&
experience&on&the&subject&of&Technical&Debt.”&
Spinola*et*al.*2013*
June&25,&2015& Copyright&©&KESL&2015& 15&
Causes&of&Technical&Debt&
TECHNOLOGY
• Technology limitations
• Legacy code
• COTS
• Changes in technology
• Project maturity
PROCESS
• Little consideration of code maintenance
• Unclear requirements
• Cutting back on process (code reviews)
• Little or no history of design decisions
• Not knowing or adopting best practices
PEOPLE
• Postpone work until needed
• Making bad assumptions
• Inexperience
• Poor leadership/team dynamics
• No push-back against customers
• “Superstars” – egos get in the way
• Little knowledge transfer
• Know-how to safely change code
• Subcontractors
PRODUCT
• Schedule and budget constraints
• Poor communication between
developers and management
• Changing priorities (market information)
• Lack of vision, plan, strategy
• Unclear goals, objectives and priorities
• Trying to make every customer happy
• Consequences of decisions not clear
Lim*et*al.*2012*
June&25,&2015& Copyright&©&KESL&2015& 16&

11. Managing&Technical&Debt& February&2015&
Copyright&©&2015&by&Philippe&Kruchten& 9&
Tensions&/&Factors&to&Consider&
• Engineers&don’t&like&technical&debt&
& &they'want'to'be'technically'flawless''
• Project&managers&or&business&people&don’t&mind&
technical&debt&
& &they'want'to'capture'market'share'
• However,&tolerance&for&TD&changes&over&the&
system&lifeJme&of&the&system&
Lim*et*al.*2012*
June&25,&2015& Copyright&©&KESL&2015& 17&
WTF/min&

12. Managing&Technical&Debt& February&2015&
Copyright&©&2015&by&Philippe&Kruchten& 10&
Visible&
New&features&
Technological&gap&
Architectural&debt&
Structural&debt& Code&smells&
Defects&Low&internal&quality&
AddiJonal&funcJonality& Low&external&quality&
Mostly&invisible&
Test&debt&
DocumentaJon&debt&
EvoluJon&issues:&evolvability& Quality&issues:&maintainability&
Visible&
architecture' code'
Code&complexity&
Coding&style&violaJons&
Zürich,&May&2012&
June&25,&2015& Copyright&©&KESL&2015& 19&
Technical&Debt&(1)&
12&
12&
a*
$15*
$5*
12&
b*
$16*
$3*
12& $18*
$20* $19* $18*
June&25,&2015& Copyright&©&KESL&2015& 20&

13. Managing&Technical&Debt& February&2015&
Copyright&©&2015&by&Philippe&Kruchten& 11&
Technical&Debt&(2)&
12&
12&
a*
$15*
$5*
12&
b*
$16*
$3*
12& $18*
8& 8& $5* 8& $8* 8& $10*
$25* $27* $28*
June&25,&2015& Copyright&©&KESL&2015& 21&
Technical&Debt&(3)&
12&
12&
a*
+$2*
$5*
12& $18*
8& 8& $5*
$30*
June&25,&2015& Copyright&©&KESL&2015& 22&

14. Managing&Technical&Debt& February&2015&
Copyright&©&2015&by&Philippe&Kruchten& 12&
Technical&Debt&
• Defect&=&Visible&feature&with&negaJve&value&
• Technical&debt&=&Invisible&feature&with&
negaJve&value&
• Cost&….&&&of&fixing&&
• Value&….&of&repaying&technical&debt,&interests&
loss&of&producJvity,&etc.&
June&25,&2015& Copyright&©&KESL&2015& 23&
TD:&negaJve&value,&invisible&
New*features*
Added*
funcNonality*
Architectural,*
Structural*
features*
Defects* Technical*
Debt*
Visible& Invisible&
PosiJve&
Value&
NegaJve&
Value&
June&25,&2015& Copyright&©&KESL&2015& 24&

15. Managing&Technical&Debt& February&2015&
Copyright&©&2015&by&Philippe&Kruchten& 13&
Interests&
• In&presence&of&technical&debt,&
&cost&of&adding&new&features&is&higher;&
&velocity&is&lower.&
• When&repaying&(fixing),&addiJonal&cost&for&
retrofixng&already&implemented&features&
• Technical&debt&not&repaid&=>&lead&to&increased&
cost,&forever&
• Cost&of&fixing&(repaying)&increases&over&Jme&
M.*Fowler,*2009*
June&25,&2015& Copyright&©&KESL&2015& 25&
Deferring&implementaJon:&
Value&decreases&
Time&
R1& R2& R3& R4&
8&
8& 7.5& 7& 6&
June&25,&2015& Copyright&©&KESL&2015& 26&

16. Managing&Technical&Debt& February&2015&
Copyright&©&2015&by&Philippe&Kruchten& 14&
But&technical&debt&increases&over&
Jme&
Time&
R1& R2& R3& R4&
Z8&
Z8& Z8.5& Z9& Z10&
June&25,&2015& Copyright&©&KESL&2015& 27&
It’s&only&a&Metaphor!&
• Metaphors&give&meaning&to&form,&help&ground&
our&conceptual&systems.&
• CogniJve&transfer:&source&domain&to&target&
domain&
– &the&<target>&is&the&<source>&
• Do'not'push'any'metaphor'too'far….'
Lakoff*and*Johnson*(1980)*Metaphors*we*live*by**
June&25,&2015& Copyright&©&KESL&2015& 28&

17. Managing&Technical&Debt& February&2015&
Copyright&©&2015&by&Philippe&Kruchten& 15&
Where&the&metaphor&breaks&
• Technical&debt&does&not&always&have&to&be&
repaid&
• What&does&it&mean&to&be&“debt&free”?&
– TD&has&a&large&part&of&subjecJvity&
• NegaJve&connotaJon&
• May&increase&the&value&of&a&project&for&a&Jme&
• Tech&Debt&as&Investment?&
June&25,&2015& Copyright&©&KESL&2015& 29&
Where&the&metaphor&breaks&
• IniJal&investment&at&T0&in&an&environment&E0.&
Now&in&T2,&E&has&changed&to&E2,&a&mismatch,&
has&occurred,&which&creates&a&debt.&&
– The&debt&is&created&by&the&change&of&environment.&
The&right&decision&in&the&right&environment&at&
some&Jme&may&lead&to&technical&debt.&
• Prudent,&inadvertent&
June&25,&2015& Copyright&©&KESL&2015& 30&

18. Managing&Technical&Debt& February&2015&
Copyright&©&2015&by&Philippe&Kruchten& 16&
Where&the&metaphor&breaks…&
• Technical&debt&depends&on&the&future&
• Technical&debt&cannot&be&measured&
• You&can&walk&away&from&technical&debt&
• Technical&debt&should&not&be&completely&
eliminated&
• Technical&debt&cannot&be&handled&in&isolaJon&
• Technical&debt&can&be&a&wise&investment&
June&25,&2015& Copyright&©&KESL&2015& 31&
PotenJal&vs.&actual&debt&
• PotenJal&debt&
– Type&1:OK&to&do&with&tools&(see&Gat&&&co.&
approach)&
– Type&2:&structural,&architectural,&or&technological&
gap:&Much&harder&
• Actual&debt&
– When&you&know&the&way&forward&
K.Schmid*2013*
June&25,&2015& Copyright&©&KESL&2015& 32&

19. Managing&Technical&Debt& February&2015&
Copyright&©&2015&by&Philippe&Kruchten& 17&
TD&litmus&test&
• If&you&are&not&incurring&any&interest,&then&it&
probably&is&not&a&debt&
McConnell*2013*
June&25,&2015& Copyright&©&KESL&2015& 33&
Technical&debt&
as&an&investment&?&

20. Managing&Technical&Debt& February&2015&
Copyright&©&2015&by&Philippe&Kruchten& 18&
TD&and&Real&OpJons&
P1:& S0&
Market&loves&it&
+&$4M&
Market&hates&it&
+&$1M&
S1&
NPV&(P1)&=&Z2M&+&0.5x4M&+&0.5x1M&=&0.5M&
Z2M&
p=0.5&
p=0.5&
Source:*K.*Sullivan,*2010*
at&&TD&Workshop&SEI&6/2Z3&
June&25,&2015& Copyright&©&KESL&2015& 35&
TD&and&Real&OpJons&(2)&
P2:& S0&
Market&loves&it&
Market&hates&it&
+&$1M&
Sd&
NPV&(P2)&=&Z1M&+&0.5x3M&+&0.5x1M&=&1M&
Z1M&
Source:&K.&Sullivan,&2010&
p=0.5&
p=0.5&
Z1M&
S1& +4M&
Taking&Technical&Debt&has&increased&system&value.&
June&25,&2015& Copyright&©&KESL&2015& 36&

21. Managing&Technical&Debt& February&2015&
Copyright&©&2015&by&Philippe&Kruchten& 19&
TD&and&Real&OpJons&(3)&
P2:& S0&
Market&loves&it&
Market&hates&it&
+&$1M&
Sd&
NPV&(P3)&=&Z1M&+&0.67&x&2.5M&+&0.33&x&1M&=&1M&
Z1M&
p=0.33&
p=0.67&
Z1.5M&
S1& +4M&
More&realisJcally:&
Debt&+&interest&
High&chances&of&success&
Take&Debt&
Repay&debt&
June&25,&2015& Copyright&©&KESL&2015& 37&
TD&and&Real&OpJons&(3)&
P2:& S0&
Market&loves&it&
Market&hates&it&
+&$1M&
Sd&
NPV&(P3)&=&Z1M&+&0.67&x&2.5M&+&0.33&x&1M&=&1M&
Z1M&
p=0.33&
p=0.67&
Z1.5M&
S1& +4M&
More&realisJcally:&
Debt&+&interest&
High&chances&of&success&
Higher&chance&
of&success&
Repay&debt&+&
50%&interest&
June&25,&2015& Copyright&©&KESL&2015& 38&

22. Managing&Technical&Debt& February&2015&
Copyright&©&2015&by&Philippe&Kruchten& 20&
TD&and&Real&OpJons&(4)&
S0&
Favourable&
Unfavourable&
Sd&
p=?&
p=?&
S1& S2&
S2d&
…..&
…..&
Not*debt*really,*but*opNons*with*different*values…**
Do*we*want*to*invest*in*architecture,*in*test,*etc…*
Refactor&
Add&feature&
Add&feature&
?&
Source:&K.&Sullivan,&2010&
June&25,&2015& Copyright&©&KESL&2015& 39&
How&do&people&“tackle”&
technical&debt&

23. Managing&Technical&Debt& February&2015&
Copyright&©&2015&by&Philippe&Kruchten& 21&
Tackling&Technical&Debt&
Axtude,&approaches&found:&
1. Ignorance&is&bliss&
2. The&elephant&in&the&room&
3. Big&scary&$$$$&numbers&
4. Five&star&ranking&
5. Constant&reducJon&
6. We’re&agile,&so&we&are&immune!&
June&25,&2015& Copyright&©&KESL&2015& 41&
Ignorance&is&bliss&
You’re&just&slower,&and&slower,&but&you&do&not&
know&it,&or&do&not&know&why&
0&
2&
4&
6&
8&
10&
12&
1& 2& 3& 4& 5& 6& 7&
FuncNonal*requirement*delivered*
IteraNons*
Velocity* accumulated&technical&debt&
impacts&ability&to&deliver&
June&25,&2015& Copyright&©&KESL&2015& 42&

24. Managing&Technical&Debt& February&2015&
Copyright&©&2015&by&Philippe&Kruchten& 22&
The&elephant&in&the&room&
• Many&in&the&org.&know&
about&technical&tech.&
• Indifference:&it’s&
someone&else’s&problem&
• OrganizaJon&broken&
down&in&small&silos&
• No&real&whole&product&
mentality&
• ShortZterm&focus&
June&25,&2015& Copyright&©&KESL&2015& 43&
Big&scary&$$$$&numbers&
• Code&smells & &167&person&days&
• Missing&test & &298&person&days&
• Design & & & &670&&person&days&
• DocumentaJon &&&67&person&days&&
&
Totals'
&Work& & & & &1,202&person&x&days&
&Cost & & & & &$577,000&
June&25,&2015& Copyright&©&KESL&2015& 44&

25. Managing&Technical&Debt& February&2015&
Copyright&©&2015&by&Philippe&Kruchten& 23&
StaJc&analysis&+&ConsulJng&
• Cu_er&ConsorJum:&Gat,&et&al.&
– Use&of&Sonar,&etc.&
– Focused&on&code&analysis&
– TD&=&total&value&of&fixing&the&code&base&
• CAST&soTware&
• ThoughtWorks&&
Debt&analysis&engagements&
Debt&reducJon&engagements&
June&25,&2015& Copyright&©&KESL&2015& 45&
Issues&
• Fits&the&metaphor,&indeed.&&
• Looks&very&objecJve…&but…&
• SubjecJve&in:&
– What&is&counted&
– What&tool&to&use&
– Cost&to&fix&
&&
Not&all&fixes&have&the&same&resulJng&value.&
Sunk&cost&are&irrelevant,&look&into&the&future&only.&
What&does&it&mean&to&be&“Debt&free”??&
June&25,&2015& Copyright&©&KESL&2015& 46&

26. Managing&Technical&Debt& February&2015&
Copyright&©&2015&by&Philippe&Kruchten& 24&
Five&star&ranking&
• Define&some&maintainability'index&
• Benchmark&relaJve&to&other&soTware&in&the&same&
category&
• ReZassess&regularly&(e.g.,&weekly)&
• Look&at&trends,&correlate&changes&with&recent&
changes&in&code&base&
• SIG&(SoTware&Improvement&Group),&Amsterdam&
• Powerful&tool&behind&
June&25,&2015& Copyright&©&KESL&2015& 47&
Constant&debt&reducJon&
• Make&technical&debt&a&visible&item&on&the&
backlog&
• Make&it&visible&outside&of&the&soTware&dev.&
organizaJon&
• Incorporate&debt&reducJon&as&a&regular&
acJvity&
• Use&buffer&in&longer&term&planning&for&yet&
unidenJfied&technical&debt&
• Lie&(?)&
June&25,&2015& Copyright&©&KESL&2015& 48&

27. Managing&Technical&Debt& February&2015&
Copyright&©&2015&by&Philippe&Kruchten& 25&
We&are&agile,&so&we’re&immune!&
In&some&cases&we&are&agile&and&therefore&we&run&faster&into&technical&debt&
June&25,&2015& Copyright&©&KESL&2015& 49&
Agile&mo_os&
• “Defer&decision&to&the&last&responsible&moment”&
• “YAGNI”&=&You&Ain’t&Gonna&Need&It&
– But&when&you&do,&it&is&technical&debt&
– Technical&debt&oTen&is&the&accumulaJon&of&too&many&
YAGNI&decisions&
• “We’ll&refactor&this&later”&
• “Deliver&value,&early”&
• Again'the'tension'between'the'yellow'stuff'and'
the'green'stuff'
• You’re'sHll'agile'because'you'aren’t'slowed'down'
by'TD'yet.'June&25,&2015& Copyright&©&KESL&2015& 50&

28. Managing&Technical&Debt& February&2015&
Copyright&©&2015&by&Philippe&Kruchten& 26&
Story&of&a&failure&
• Large&reZengineering&of&
&a&complex&distributed&&
worldZwide&system;&&
2&millions&LOC&in&C,&&
C++,&Cobol&and&VB&
• MulJple&sites,&dozens&of&data&repositories,&hundreds&
of&users,&24&hours&operaJon,&missionZcriJcal&
($billions)&
• xP+Scrum,&1Zweek&iteraJons,&30&then&up&to&50&
developers&
• Rapid&progress,&early&success,&features&are&demoZable&
• Direct&access&to&“customer”,&etc.&
• A'poster'project'for'scalable'agile'development'
June&25,&2015& Copyright&©&KESL&2015& 51&
Hixng&the&wall&
• ATer&4&½&&months,&difficulJes&&
to&keep&with&the&1Zweek&&
iteraJons&
• Refactoring&takes&longer&&
than&one&iteraJon&
• Scrap&and&rework&raJo&&
increases&dramaJcally&
• No&externally&visible&progress&anymore&
• IteraJons&stretched&to&3&weeks&
• Staff&turnZover&increases&&
• Project&comes&to&a&halt&
• Lots&of&code,&no&clear&architecture,&no&obvious&way&forward&
June&25,&2015& Copyright&©&KESL&2015& 52&

29. Managing&Technical&Debt& February&2015&
Copyright&©&2015&by&Philippe&Kruchten& 27&
MulJple&Component&Defects&
• MCD&=&A&defect&whose&fix&requires&changes&to&
mulJple&components&(large&systems)&
• MCD:&6Z10%&of&all&defects&
• 20&Jmes&more&modificaJons;&50%&more&effort&
• Fixes&2Z3&Jmes&more&likely&to&span&mulJple&
iteraJons&or&releases&
• 20%&of&components&hit&by&80%&of&MCD&
Li*et*al,*2011*
June&25,&2015& Copyright&©&KESL&2015& 53&
CogniJve&biases&and&TD&
• EscalaJon&of&commitment&
– Aka,&too&much&invested&to&quit&
• Sunk&cost&fallacy&
– aka.&throwing&good&money&aTer&
bad&
• Anchoring&
• Confirmatory&bias&
June&25,&2015& Copyright&©&KESL&2015& 54&

30. Managing&Technical&Debt& February&2015&
Copyright&©&2015&by&Philippe&Kruchten& 28&
Tools&and&Techniques&
Some&examples&
Tools&for&Technical&Debt&Analysis&
• Vendors&include&
• CAST&
• Inspearit&
• SonarSource&(Sonarqube)&
• Thoughtworks&
• SoTware&Improvement&Group&(SIG)&
• Laxx&
• Hello2morrow&
• Tocéa&(ScerJfy)&
• Xdepend&
• Klocwork&
• JetBrains&
June&25,&2015& Copyright&©&KESL&2015& 56&

31. Managing&Technical&Debt& February&2015&
Copyright&©&2015&by&Philippe&Kruchten& 29&
PropagaJon&cost&
• “Density”&of&the&DSM&&
– Proposed&by&McCormack&et&al.&in&2006&
– Several&limitaJons&as&a&tool&to&measure&T.D.&
• Improved&PC:&
– Boolean&to&conJnuous&value&(=dependency&
“strength”)&
– Changes&not&uniformly&spread&throughout&the&
code&
– Less&sensiJve&to&size&of&code&
McCormack*et*al.*2006*
June&25,&2015& Copyright&©&KESL&2015& 57&
Example&of&PC:&EvoluJon&of&Ant&
Technical'debt'reducHon'
Release&number&
June&25,&2015& Copyright&©&KESL&2015& 58&

32. Managing&Technical&Debt& February&2015&
Copyright&©&2015&by&Philippe&Kruchten& 30&
Tech&Debt&(mis)ZconcepJons&
• Technical&debt&reifies&an&abstract&concept&
• Technical&debt&does&not&equate&to&bad&quality&
• Technical&debt&can&be&induces&by&a&shiT&in&
context&
• Defects&are&not&technical&debt&
• Lack&of&progress&is&not&technical&debt&
• New&features&yet&to&be&implemented&is&not&
technical&debt&
June&25,&2015& Copyright&©&KESL&2015& 59&
Technical&Debt&DefiniJon&(2013)&
• A&design&or&construcJon&approach&
that&is&expedient&in&the&short&
term,&but&that&creates&a&technical&
context&in&which&the&same&work&
will&cost&more&to&do&later&than&it&
would&cost&to&do&now&(including&
increased&cost&over&Jme).&
McConnell*2013*
June&25,&2015& Copyright&©&KESL&2015& 60&

33. Managing&Technical&Debt& February&2015&
Copyright&©&2015&by&Philippe&Kruchten& 31&
Visible&
New&features&
Technological&gap&
Architectural&debt&
Structural&debt& Code&smells&
Defects&Low&internal&quality&
AddiJonal&funcJonality& Low&external&quality&
Mostly&invisible&
Test&debt&
DocumentaJon&debt&
EvoluJon&issues:&evolvability& Quality&issues:&maintainability&
Visible&
architecture' code'
Code&complexity&
Coding&style&violaJons&
Technical&debt&landscape&
Kruchten*et*al*2012*
June&25,&2015& Copyright&©&KESL&2015& 61&
Conclusion&
• Technical&debt&is&sJll&more&a&rhetorical'category&
than&a&technical'or&ontological&category.&&
• The&concept&&resonates&well&with&the&
development&community,&and&someJmes&also&
with&management.&
• It&bridges&the&gap&between&business&decision&
makers&and&technical&implementers.&
• It’s&only&a&metaphor;&do&not&push&it&too&far.&
• It’s&not&all&bad:&maybe&an&investment&
June&25,&2015& Copyright&©&KESL&2015& 62&

34. Managing&Technical&Debt& February&2015&
Copyright&©&2015&by&Philippe&Kruchten& 32&
Visible&
New&features&
Technological&gap&
Architectural&debt&
Structural&debt& Code&smells&
Defects&Low&internal&quality&
AddiJonal&funcJonality& Low&external&quality&
Mostly&invisible&
Test&debt&
DocumentaJon&debt&
EvoluJon&issues:&evolvability& Quality&issues:&maintainability&
Visible&
architecture' code'
Code&complexity&
Coding&style&violaJons&
June&25,&2015& Copyright&©&KESL&2015& 63&
June&25,&2015& Copyright&©&KESL&2015& 64&

35. Managing&Technical&Debt& February&2015&
Copyright&©&2015&by&Philippe&Kruchten& 33&
References&
! Brown,&N.,&Cai,&Y.,&Guo,&Y.,&Kazman,&R.,&Kim,&M.,&Kruchten,&P.,&et&al.&(2010).&Managing'
Technical'Debt'in'So)wareLIntensive'Systems.&Paper&presented&at&the&Future&of&soTware&
engineering&research&(FoSER)&workshop,&part&of&FoundaJons&of&SoTware&Engineering&(FSE&
2010)&conference.&&
! Brown,&N.,&Nord,&R.,&Ozkaya,&I.,&Kruchten,&P.,&&&Lim,&E.&(2011).&Hard&Choice:&A&game&for&
balancing&strategy&for&agility.&Paper&presented&at&the&24th&IEEE&CS&Conference&on&SoTware&
Engineering&EducaJon&and&Training&(CSEE&T&2011),&Honolulu,&HI,&USA.&
! Cunningham,&W.&(1992).&The'WyCash'PorOolio'Management'System.'Paper&presented&at&the&
OOPSLA'92&conference,&ACM.&Retrieved&from&h_p://c2.com/doc/oopsla92.html&
! CurJs,&B.,&Sappidi,&J.,&&&Szynkarski,&A.&(2012).&EsJmaJng&the&Principal&of&an&ApplicaJon’s&
Technical&Debt.&IEEE&&SoTware,&29(6).&
! Denne,&M.,&&&ClelandZHuang,&J.&(2004).&So)ware'by'Numbers:'LowLRisk,'HighLReturn'
Development,'PrenJce&Hall.&
! Denne,&M.,&&&ClelandZHuang,&J.&(2004).&The&Incremental&Funding&Method:&DataZDriven&
SoTware&Development,&IEEE'So)ware,&21(3),&39Z47.&
! Fowler,&M.&(2009),&Technical'debt'quadrant,'Blog&post&at:&
h_p://www.marJnfowler.com/bliki/TechnicalDebtQuadrant.html&&
! Gat,&I.&(ed.).&(2010).&How'to'seUle'your'technical'debtLLa'manager's'guide.&Arlington&Mass:&
Cu_er&ConsorJum.&
! Kruchten,&Ph.&(2010)&Contextualizing&Agile&SoTware&Development,”&Paper&presented&at&the&
EuroSPI&2010&conference&in&Grenoble,&Sept.1Z3,&2010&&&
June&25,&2015& Copyright&©&KESL&2015& 65&
References&
! Kruchten,&P.,&Nord,&R.,&&&Ozkaya,&I.&(2012).&Technical&debt:&from&metaphor&to&theory&and&pracJce.&
IEEE''So)ware,&29(6).&&
! Kruchten,&P.,&Nord,&R.,&Ozkaya,&I.,&&&Visser,&J.&(2012).&Technical&Debt&in&SoTware&Development:&from&
Metaphor&to&TheoryZZReport&on&the&Third&InternaJonal&Workshop&on&Managing&Technical&Debt,&
held&at&ICSE&2012&ACM'SIGSOFT'So)ware'Engineering'Notes,&37(5).&&
! Li,&Z.,&Madhavji,&N.,&Murtaza,&S.,&Gi_ens,&M.,&Miranskyy,&A.,&Godwin,&D.,&&&Cialini,&E.&(2011).&
CharacterisJcs&of&mulJpleZcomponent&defects&and&architectural&hotspots:&a&large&system&case&
study.&Empirical'So)ware'Engineering,&16(5),&667Z702.&doi:&10.1007/s10664Z011Z9155Zy&
! Lim,&E.&(2012).&Technical'Debt:'What'So)ware'PracHHoners'Have'to'Say.'(Master's&thesis),&
University&of&BriJsh&Columbia,&Vancouver,&Canada.&&&&
! Lim,&E.,&Taksande,&N.,&&&Seaman,&C.&B.&(2012).&A&Balancing&Act:&What&SoTware&PracJJoners&Have&to&
Say&about&Technical&Debt.&IEEE''So)ware,&29(6).&
! MacCormack,&A.,&Rusnak,&J.,&&&Baldwin,&C.&Y.&(2006).&Exploring&the&structure&of&complex&soTware&
designs:&An&empirical&study&of&open&source&and&proprietary&code.&Management'Science,'52(7),&
1015Z1030.&&
! Nord,&R.,&Ozkaya,&I.,&Kruchten,&P.,&&&Gonzalez,&M.&(2012).&In&search&of&a&metric&for&managing&
architectural&technical&debt.&Paper&presented&at&the&Working'IEEE/IFIP'Conference'on'So)ware'
Architecture'(WICSA'2012),&Helsinki,&Finland.&
! McConnell,&S.&(2007)&Notes'on'Technical'Debt,&Blog&post&at:&h_p://blogs.construx.com/blogs/
stevemcc/archive/2007/11/01/technicalZdebtZ2.aspx&
! Special&issue&of&CuUer'IT'Journal&on&Technical&Debt,&edited&by&I.&Gat&(October&2010)&Cu_er&IT&
Journal,&23&(10).&
! Sterling,&C.&(2010)&Managing'So)ware'Debt,&AddisonZWesley.&
June&25,&2015& Copyright&©&KESL&2015& 66&

36. Managing&Technical&Debt& February&2015&
Copyright&©&2015&by&Philippe&Kruchten& 34&
References&(cont.)&
! R.&O.&Spinola,&N.&Zazworka,&A.&Vetrò,&C.&B.&Seaman,&and&F.&Shull,&"InvesJgaJng&Technical&Debt&
Folklore:&Shedding&Some&Light&on&Technical&Debt&Opinion,"&in&Proceedings&of&the&4th&
Workshop&on&Managing&Technical&Debt,&at&ICSE&2013,&P.&Kruchten,&I.&Ozkaya,&and&R.&Nord,&
Eds.,&IEEE,&2013.&
! K.&Schmid,&"On&the&Limits&of&the&Technical&Debt&Metaphor,"&in&&Proceedings&of&the&4th&
Workshop&on&Managing&Technical&Debt,&at&ICSE&2013,&P.&Kruchten,&I.&Ozkaya,&and&R.&Nord,&
Eds.,&IEEE,&2013,&pp.&63Z66.&
! K.&Schmid,&"A&Formal&Approach&to&Technical&Debt&Decision&Making,"&in&Proceedings&of&the&
Conference&on&Quality&of&SoTware&Architecture&QoSA'2013,&Vancouver,&2013,&ACM.&
June&25,&2015& Copyright&©&KESL&2015& 67&
Other&sources&(Talks/slides)&
• Gat,&I.,&Heintz,&J.&(Aug.&19,&2010)&Webinar:'Reining'in'Technical'Debt,&
Cu_er&ConsorJum.&
• McConnell,&S.&(October&2011)&Managing&technical&debt.&(Webinar)&&
• Kniberg,&H.&(2008)&Technical'debtLHow'not'to'ignore'it,&at&Agile&2008&
conference.&
• Kruchten,&P.&(2009)&What'colour'is'your'backlog?'Agile&Vancouver&
Conference.&h_p://philippe.kruchten.com/talks&
• Sterling,&C.&(2009)&h_p://www.slideshare.net/csterwa/managingZ
soTwareZdebtZpnsqcZ2009&
• Short,&G.&(2009)&h_p://www.slideshare.net/garyshort/technicalZ
debtZ2985889&
• West,&D.&(January&2011),&Balancing'agility'and'technical'debt,&Forrester&&&
Cast&SoTware&
June&25,&2015& Copyright&©&KESL&2015& 68&

37. Managing&Technical&Debt& February&2015&
Copyright&©&2015&by&Philippe&Kruchten& 35&
Other&sources&
• Slides&on&Sonar,&from&Olivier&Gaudin,&CEO&of&Sonarqube'
• Slides&on&SQALE&from&JeanZLouis&Letouzey,'Inspearit'
• Slides&on&DSM&from&Ipek&Ozkaya&and&Robert&Nord,&SEI'
June&25,&2015& Copyright&©&KESL&2015& 69&
June&25,&2015& Copyright&©&KESL&2015& 70&