Deep conversations with domain experts and careful attention to the language are central in software development and in particular in Domain-Driven Design (DDD). However it takes many years and many failures to get better at this game. Still, over time it is possible to extract a growing set of techniques and heuristics that can boost the effectiveness of the interviews with domain experts, to learn faster and converge quickly to better models. There are techniques and heuristics for asking better questions, listening carefully to words and other signals, and for managing credibility as a developer facing business experts. If you think all the above is important, then these interviewing techniques will improve your skills, step up the quality of your collaboration with your domain experts, and will provide benefits for better domain models. And if you find all that boring, then perhaps you could focus your career on Java EE instead.

1. @cyriux
CyrilleMartraire
Interviewing Domain
Experts: heuristics
from the trenches
1

2. Osmo Wiio

3. “Communications
usually fails, except
by accident.”
Wiio’s law

4. Perhaps he didn’t mean
that…
Or perhaps he did mean
that…
https://en.wikipedia.org/wiki/Wiio%27s_laws

5. Imagine

6. Hi Domain Expert!

7. Tell us what I need
to know to build the
software

8. Hi kids, I
don’t have time for
that. I’ve already sent
you what I want by
email.

9. #FAIL
SCARY

10. Could be worse

11. Tell us what I need
to know to build the
software

12. Sure, I want a red
button to save data in
table T_DEAL_2

13. #FAIL
blood-
curdling

14. My brain has limited
capacity.
Bad News

15. People are people.
Business domains are
complex (complicated?)
Moar Bad News

16. A while ago
In a large French bank

17. Weekly DDD
Book Club

18. Weekly DDD
Book Club
What? Talking
to experts is a
thing now?

19. Weekly DDD
Book Club
You can learn
that?

21. Domain experts hate him:
=ind how this guy learns
the domain faster with a
simple trick.

23. Passionate
developer
PARIS
Since 1999
@cyriux
Cyrille Martraire

24. Paris Software
Craftsmanship Community
http://www.meetup.com/paris-software-craftsmanship/

25. TDD
BDD
DDD arolla.fr
@arollafr

26. CONGRATS!
YouWILLMEETTHE
DOMAINEXPERT

29. “We don’t talk the
same language.”

30. “They don’t have
time for us.”

31. Haz
Expertise
Haz
Time

32. Haz
Expertise
Haz
Time
their time
is precious

33. Haz
Expertise
Haz
Time
Don’t waste
their time

34. Don’t go
naked

35. Teach Yourself some
Domain Knowledge!

36. It all starts with curiosity
36

37. It all starts with curiosity
37
genuine

39. My brain has limited
capacity: I need some time
to learn.

40. Do your homework

41. The
Official
Domain
Bible

42. Civil Case Type
<FiduciaryTypeCode>*
<JurisdictionalGroundsCode>
<ReliefTypeCode>
Domestic Case Type
<NoContactCode>*
<RequestToVacateCode>
Common Types
<AliasAlternateNameTypeCode>*
<CaseAssociationTypeCode>*
<CaseOfficialRoleText>*
<CaseParticipantRoleCode>*
<CauseOfActionCode>
<CourtEventTypeCode>
<EntityAssociationTypeCode>
<ErrorCode>* Juvenile Case Type
<DelinquentActApplicabilityCode>
<DelinquentActDegreeCode>
<DelinquentActSeverityCode>
<DelinquentActSpecialAllegationCode>
<DependencyAllegationCode>
<GuardianAssociationTypeCode>*
<PlacementTypeCode>
...
http://docs.oasis-open.org/legalxml-courtfiling/specs/ecf/v4.01/ecf-v4.01-spec/os/ecf-v4.01-spec-os.pdf
Electronic Court Filing Ver
OASIS Standard
23 May 2013
Specification URIs
This version:
http://docs.oasis-open.org/legalxml-courtfiling/specs/ecf/v4
os.doc (Authoritative)
http://docs.oasis-open.org/legalxml-courtfiling/specs/ecf/v4
os.html
http://docs.oasis-open.org/legalxml-courtfiling/specs/ecf/v4
os.pdf
Previous version:
http://www.oasis-open.org/committees/download.php/4564
Latest version:
http://docs.oasis-open.org/legalxml-courtfiling/specs/ecf/v4
(Authoritative)
http://docs.oasis-open.org/legalxml-courtfiling/specs/ecf/v4
http://docs.oasis-open.org/legalxml-courtfiling/specs/ecf/v4
Technical Committee:
OASIS LegalXML Electronic Court Filing TC
Chairs:
James Cabral (jcabral@mtgmc.com), MTG Management C
Jim Harris (jharris@ncsc.org), National Center for State Co
Editors:
Adam Angione (aangione@courthousenews.com), Courtho
James Cabral (jcabral@mtgmc.com), MTG Management C
Additional artifacts:
This prose specification is one component of a Work Produ
XML schemas:
http://docs.oasis-open.org/legalxml-courtfiling/specs/ec

43. 3.3 Outline
This high-level process model i
experience
For clarity, the whole process c
election, election, post election;
processes.
• Pre election
• Election (100)
• Candidates (200)
• Options (600)
• Voters (300)
• Election
• Voting (400)
• Post election
• Results (500)
• Audit
• Analysis
Some functions belong to the w
• Administration Interface
• Help Desk
http://docs.oasis-open.org/election/eml/v5.0/os/EML-Process-Data-Requirements-v5.0.html
Election Markup Language

44. http://docs.oasis-open.org/emergency/edxl-have/v1.0/errata/edxl-have-v1.0-os-errata-os.html
Emergency Data Exchange

45. OK
Domain Overview
Checklist of potential questions
Corpus of vocabulary
NOT OK
Ready-made solutions
Features list
The Truth (TM)

46. Hi Domain Expert!

47. First I’d
like to better
understand how an
insurance policy
works

48. Ok, so basically
it starts with a
contract… <useful
stuff here>

49. Now we have a
conversation
#WIN

50. Successful people are
curious about their
business domains.
You won’t believe how
this can help you too!

51. My brain has limited
capacity: I need to write to
remember.

52. Note-taking
like a pro!

53. ”The visitor
requests an
insurance quote”

54. “The user asks a quote”

55. Not what he said!

56. LOST knowledge

57. LOST opportunity
to learn

58. “The user asks a quote”
visitor

59. “The user asks a quote”
requests

60. “The user asks a quote”
insurance

62. ACTIVE
LiSTENING

63. Harder than you’d
think
Turn it into a game

64. WORD
SAFARI

65. The trader makes a
deal …

66. the trader makes a
deal

67. the trader makes a
deal
new word

68. Could you define
”Deal”?

69. …

70. Then the trade is
booked in a
particular
portfolio.

71. So the trader makes a
deal. Then the trade is
booked in a particular
portfolio.

72. So the trader makes a
deal. Then the trade is
booked in a particular
portfolio.
synonyms?

73. You talked
about ”deal” and
”trade” as if they
were the same
thing…

74. Is there any
difference?

75. Now we’re talking!
And learning some
real useful stuff.
#WIN

76. 76
Meh.
it’s just a simple
trick…

77. No, this is
important

78. *This* is DDD

79. Let’s move on…

80. On execution the
remaining order fill is
reduced by its size.

81. On execution the
remaining order fill is
reduced by its size.
new word

82. You’re talking
about ”order” and
”execution”.

83. I know that an
order is like a
request to trade, what
about the
execution?

84. I know that an
order is like a
request to trade, what
about the
execution?

85. Showing interest and
some amount of
knowledge here

86. ESTABLISH
CREDIBILITY

88. Show your genuine
curiosity
Ask better questions
Challenge respectfully
88

89. Talking to people is hard
89
But there’s an antidote…

90. 90
Interactive Conversations

91. 91
Interactive Conversations
You have control

92. STEERING
CONVERSATIONS

93. Don’t interrupt.
Write questions for
later.

94. Then the trade is saved
in a particular
portfolio”
My note-taking syntax
new word

95. Then the trade is saved
in a particular
portfolio”
[Check Wikipedia on trading]
My note-taking syntax
*MY* remarks
not clear

96. Then the trade is saved
in a particular
portfolio”
My note-taking syntax
Q: When is this done?
question for later

97. http://katrinatester.blogspot.fr/2014/08/how-to-create-visual-test-coverage-model.html
Learn from testers
@JamesMarcusBach
@Katrina_tester

98. Scan your notes while
listening to decide on
next questions.

99. Navigating the
conversation

100. Our map of concepts
http://www.infoq.com/articles/conversation-patterns-3
invoice
paper e-invoice
partner
chasing

101. invoice
paper e-invoice
partner
chasing
depth Vs breadth
http://www.infoq.com/articles/conversation-patterns-3
Conversation Patterns for Software Professionals
Michał Bartyzel

102. paper e-invoice
partner
chasinginvoice
Summarizing + intent
http://www.infoq.com/articles/conversation-patterns-3

103. Image Found on Google Images; Credited to www.s-curiosity.com

104. We need a print
button on this
screen.

105. WHY?

106. Let me check to the
users…

107. …

108. They need to give
printouts to another
department.

109. WHY?

110. Because they need
to type the data into
their system.

111. WTF!

112. Start with ”what’s
the goal?”

113. Reverse-engineer the
true need from the
expressed solution

115. But don’t go too far…

116. invoice
paper e-invoice
partner
chasing
Concrete Details
http://www.infoq.com/articles/conversation-patterns-3

118. I think we agree,
but to be sure we
should have an
example

119. BDD: your best friend to
interview domain experts

120. Discover early
unknown unknowns
+
misunderstanding
#WIN

121. Asking for concrete
examples
Why is it so hard?

122. Talking abstract is
faster

123. Is it faster when
we’re wrong or
missing stuff that
matters?

124. http://www.hometalkusa.com/Tips/sample_construction_contract.htm
Ask for genuine sample
documents / data

125. Ask for genuine sample
documents / data

126. Ask for genuine sample
documents / data
Ask! Insist!

127. Exploring
http://www.infoq.com/articles/conversation-patterns-3
invoice
paper e-invoice
partner
chasing
…

128. bla bla bla shopping
cart…

129. And by the way this
is not the case for the
marketplace

130. And by the way this
is not the case for the
marketplace

131. bla bla bla shopping
cart…
Q: marketplace???

132. Take note of side
remarks

133. marketplace
shopping cart

134. In real life…

135. the
Domain
Expert
Delusion

136. THE ALMIGHTY EXPERT

137. DOES NOT EXIST

140. The worst domain
expert is the one whose
expertise was built from
the intricacies of the
existing systems

142. We can help.

143. EMPATHYput yourself in their shoes

144. EMPATHYput yourself in their shoes
Figuratively

145. EMPATHYput yourself in their shoes
Figuratively & Literally

148. PARTNERSHIP
Two-Ways Conversations

150. "The best way to get the
right answer on the Internet
is not to ask a question, it's
to post the wrong answer.”
— Cunningham’s Law

151. PROPOSEas-a-tactic

152. Propose
something.
152

153. Propose
something.
153
Doesn’t have to be
right / complete
But do your
best anyway

154. "Given a
shopping basket which
is over the free shipping
limit, when I go to checkout
the basket, what should I see
on the screen?"
Liz Keogh: http://www.infoq.com/articles/pulling-power

155. "Oh… Shipping is FREE
with this order!"
Liz Keogh: http://www.infoq.com/articles/pulling-power

156. Got it!
Given a shopping basket which is
over the free shipping limit
When I go to checkout the basket
Then I am notified that "shipping
is FREE with this order"

157. The interview is over
for today.
Next is tomorrow.

158. SPIKE

160. Kitten kitty = new Kitten(Attitude.ROCK_STAR);
Microphone mike = new Microphone();
kitty.sing(mike);
system.out.println(mike.playBack());
//”mew mew meeew”

161. My brain has limited
capacity: I need executable
code & its tests to see issues.

162. Code ☛ Issues +
Questions
Perfect for better
questions for the next
interview!
#WIN
Greg Young codeanalysis
http://skillsmatter.com/podcast/design-architecture/mystery-ddd/js-4401

163. Teach Yourself
Active
Listening
Code
leading
to new
questions
Learn
Together
Propose
WITH the
EXPERT
WITHOUT
the EXPERT

164. My brain has limited
capacity: I need some sleep
to see things more clearly.

165. Deeper
Insights
Iterate over time

166. Deeper
Insights
Iterate over time

167. 167
WHY bother
so much?

168. The Complexity of
the Domain is there
http://www.leunig.com.au

169. You can ignore the
domain complexity,
but it won’t ignore you

170. http://www.leunig.com.au
DELIBERATE
DISCOVERY!

172. The obligatory
exercise for the
audience

173. You’re all domain
experts too!

174. Pants!

175. Pants!
Give a clear definition
2mn

176. Tacit
Mental Models

177. What would happen if
<change something>?

178. Need more examples.

180. ”You idiot! It’s to cover
the ass of course!”

181. Ooops!

182. It’s to cover the ass?

183. Cover the ass: fixed!

184. No ass, no pants?

185. ”It’s easy! It’s to cover
the legs of course!”

187. To cover legs, really?

189. A deep definition would
answer this question

190. (I don’t have the
answer)

191. Got more
secret
techniques?

192. DRAW FROM
YOUR TOOLBOX

193. A Good Investment

194. Learn some maths
(monoids…)
194
A Good Investment

195. Could we
say that?
HotelBooking
Jan26to27 HotelBooking
Jan27to29
HotelBooking
Jan26to29
+
=

196. Past work experience,
from any domain.
196
A Good Investment

197. Knowledge of other domains
often introduces surprising
insights into a project […]
[…] things like core accounting
patterns crop up in places that
don't look like accounting on the
surface.
http://lizkeogh.com/2015/12/14/bdd-a-three-headed-monster/
- Liz Keogh

198. Businesses don’t want all
powers concentrated into
the same hands
198

199. Astonishment as-a-tool
199
I’m
surprised, I was
expecting a
segregation of
duties here

200. Assume + Probe
200
Oops, you’re right!
My bad.

201. Businesses don’t usually
like ”hard delete”
201

202. Probe
202
Can we *really*
delete the entry?

203. No no. We add
another entry to
compensate it.

204. Faster Discovery
204

205. INVARIANTS

206. “Is there any other
outcome that’s
important?”
Liz Keogh

207. So the budget is
the sum of all the
tickets, right?

208. Yes.

209. Is it always
true? Is there a case
where it would not
be true?

210. Well, yes. Some
attendees do not pay,
and some donate
more.

211. And we have
sponsors too…

212. Tickets: OK
Donations
Non paying attendees
Sponsors
New concepts

213. Tickets: OK
Donations
Non paying attendees
Sponsors
#WIN

214. Bounded
Contexts
Heuristics

215. Multiple Domain Experts?
215

216. The plural of domain
expert is ”confusion”

217. Or potential Bounded
Contexts
217

218. Scalar
/ Record
List
Tree
Graph
Different Shape
Different Bounded Context

219. 219
What happens if
there’s a cycle?

220. I don’t get it;
there can’t be any
cycle…

221. Different shapes ->
Bounded Contexts
221

222. BONUS
TIPS

223. http://rainbowmonkey9.deviantart.com/art/ERR-UM-AH-K-UM-129680498

224. Shall we sort by
date or by price?

225. Um… Err… I’d say by
date…

226. ”Sort by date”
[Not convincing]

227. Expect change ➔ Design
with a Comparator
Little bit of
speculation here!

228. Hesitation -> Design
Expect change ➔ Design
with a Comparator

229. MIND THE
LOGISTICS

230. Important screenshots /
diagrams close to hands
”I mean HERE”

233. This place is magic

234. All on the same side

235. Can sketch together!

236. DOMAIN-
SPECIFIC
NOTATIONS

237. http://cset.sp.utoledo.edu/~nkissoff/lessons/Lesson2.html
Financial cash flows

238. Music

239. https://en.wikipedia.org/wiki/Kinematic_diagram
Kinematic

240. http://www.scdigest.com/assets/Experts/Guest_09-02-18-1.php
Supply Chain Management

241. http://strategic.mit.edu/spacelogistics/optimization.php
Space Mission Optimization

242. http://dance.lovetoknow.com/Rumba_Dance_Step_Diagram
Dancing

244. In closing

245. https://leanpub.com/livingdocumentation
BUY MY BOOK!

246. In closing

247. Just examples.
Live your own life.
Build your own toolbox.
247

249. just tell me what I
need to code!

250. I'm
an architect, I
will impress you with
my technical
brilliance

251. I'm smarter than
the business guys!

252. THE RULE
Make it clear they are safe
with you.
e.g. you have no plan to
steal their job.

253. THE RULE
ALWAYS ask for
validation of everything
(even if you’re sure).

254. Talking to
Domain Experts
is a thing now!

255. I have to tell you a
secret

256. I choose projects based on their
potential for applying DDD
256
Rich Business Domain
Software as a differentiator

257. I choose projects based on the
people too.
257
Clear Vision
Collaborative mindset

258. "Dude, you are just a
programmer." But I don't
think that's true
@JefClaes at #BuildStuffLT
— @selketjah

259. Proposing ideas
not just as a tactic,
but also suggesting genuinely
valuable business ideas
259

260. 260
Good models have
Predictive Power

261. Suggest
FEATURES
from the
CODE

262. 262
DDD: Software to
support the domain
DDD: Software-
augmented domain

263. “If one group of people does
market research and makes
product decisions, and another
group that develops the
software, we have less
integrated understanding.”
— Symbiosis - A Provocation About Organizations
Michael Feathers, R7K Research & Conveyance
https://drive.google.com/file/d/0B8ZX1RoWHuiJRnppcERLNjdSV00/view

264. #WIN!

265. Event Storming
workshops
@mathiasverraes@ziobrando

266. Mob-Programming
@woodyzuill

267. @woodyzuill
Domain
Expert
Mob-Programming

269. Merci !
h,p://cathy313.centerblog.net/539-bisounours

270. Follow me @cyriux
Slides: slideshare.net/cyriux
Blog: cyrille.martraire.com
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