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Architectural Decision Making; What Happens Behind theScenes?
by Gerrit Muller Buskerud University Collegee-mail: [email protected]
www.gaudisite.nl
Abstract
Many decisions are taken during the architecting of a system. The question iswhat are architectural decisions? And what is the process behind making thesedecisions? The expectations of the stakeholders will be discussed. The actualway of working of architects will be described.
Distribution
This article or presentation is written as part of the Gaudí project. The Gaudí projectphilosophy is to improve by obtaining frequent feedback. Frequent feedback is pursued by anopen creation process. This document is published as intermediate or nearly mature versionto get feedback. Further distribution is allowed as long as the document remains completeand unchanged.
October 20, 2017status: draftversion: 0.2
architecture decision
system
architect
Figure Of ContentsTM
architecture decision
system
architect
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ADMpresentationIcon
Buzzword, Hype, Solution or What?
architecture decision
system
architect
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ADMpresentationIconArchitecture
What is Architecture?
market, business, technology
process, product
components
(implementations)
API's
OS file system
bus memory I/O
infrastructurehttp DVB IPTV
WMA MP3 JPEG
standards
audio
pipeline
message
routing
whiteboard
communication
concepts
layer n !calls n-k; k>1
layer n !calls n+k; k>0
high level rules
customers environment
Java
SQL
FPGAtechnology
domain
codification
overarching vision
Spec Design
DesignDesign
SpecSpec
specifications
guidance
monitoring
indicators
Mark all applicable boxes
other...
performance
reliability
costrisk
functionality
power
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HMPAwhatIsArchitecture
Architecture vs Description
Architecture
Subset of which architect is aware
Architecture description
Actually written by architect(s)
Flattened into
Architectural Decision Making; What Happens Behind the Scenes?5 Gerrit Muller
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VCarchitectureDescription
My View on Architecture
Do the right things
Do the things right
HowGuiding
WhyUnderstanding
WhatDescribing
Architectural Decision Making; What Happens Behind the Scenes?6 Gerrit Muller
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LWAwhatIsArchitecture
”Guiding How” by providing rules for:
4. Infra-
structure
2. Construction
Decomposition
3. Allocation
5. Choice of
integrating
concepts
1. Functional
Decomposition
tunerframe-
bufferMPEG
DS
PCPU RAM
drivers scheduler OS
etc
audio video TXTfile-
systemnetworkingetc.
view play browse
storage
acquisition compress encoding
displayde-
compressdecoding
Resource
usagePerformance
Exception
handling
Device
abstraction
Pipeline
Architectural Decision Making; What Happens Behind the Scenes?7 Gerrit Muller
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LWAarchitectureHow
The Art of Architecting
Intuition, assumptions, beliefs, bias
Expectations
Facts
Architecture(s)
Architecture
Architect(s)
Stakeholders
analyze
assess
balance
trade-off
decide
vision
overview
insight
understanding
Architecting
problems, legacy
uncertainties
unknowns
Facts, Expectations and
Intuition may be false
Integration requires a
critical mindset that is alert
for unknowns
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LWAarchitecting
Another Buzzword or Solution?
architecture decision
system
architect
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ADMpresentationIconDecision
Question
How many (architectural) decisionsdoes an architect make?
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Decision Making Process
1. Problem understanding
2. Analysis
3. Decision
4. Monitor, verify, validate
insu
fficie
nt d
ata
no
sa
tisfy
ing
so
lutio
n
inva
lida
ted
so
lutio
n
co
nflic
ting
oth
er d
ecis
ion
vague problem statement
Architectural Decision Making; What Happens Behind the Scenes?11 Gerrit Muller
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Decision Making Process Annotated
1. Problem understanding by
exploration and simple models
2. Analysis by
+ exploring multiple propositions (specification + design proposals)
+ exploring decision criteria (by evaluation of proposition feedback)
+ assessment of propositions against criteria
3. Decision by
+ review and agree on analysis
+ communicate and document
4. Monitor, verify, validate by
+ measurements and testing
+ assessment of other decisions
insu
fficie
nt d
ata
no
sa
tisfy
ing
so
lutio
n
inva
lida
ted
so
lutio
n
co
nflic
ting
oth
er d
ecis
ion
vague problem statement
Architectural Decision Making; What Happens Behind the Scenes?12 Gerrit Muller
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Graph of Decisions and Alternatives
scope of architect's considerations
communication scope
past decision
most probable decision potential alternative less probable alternative
legend
time now
Architectural Decision Making; What Happens Behind the Scenes?13 Gerrit Muller
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Different Types of Decisions
How Guiding
Why Understanding
What Describing
basic principles requirements
architecture rules implementation choices
f.i. technology
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ADMdecisions
Many Decisions are taken in the Dark
fact
ual k
now
ledg
e
deci
sion
impa
ct
time
Highest impact decisions are taken while the least factual knowledge is available
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ADMdecisionFoundation
Chicken or Egg?
decision
action
trigg
ers
prov
ides
dat
a
wai
t for
de
cisi
on
wai
t for
kn
owle
dge
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ADMchickenOrEgg
Why Project Leaders Sometimes don’t like Architects
decision
action
trigg
ers
prov
ides
dat
a
wai
t for
de
cisi
on
wai
t for
kn
owle
dge
Highest impact decisions are taken while the least factual knowledge is available
Facts, Expectations and Intuition might be false
Intuition
Expectations
Facts
Architecture(s) Architecture
Architect(s)
Stakeholders
analyze assess balance trade-off decide
vision overview
insight understanding
Architecting
decision - action chicken or egg?
number of decision taken
perc
eive
d pr
ogre
ss
fact
ual k
now
ledg
e
deci
sion
impa
ct
time
by project leader
by system architect
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ADMperceivedProgress
Bottom-line is a Working System
architecture decision
system
architect
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ADMpresentationIconSystem
Decisions Are Related
C ustomer objectives
A pplication F unctional C onceptual R ealization
why? what?
how? how? what?
why?
how?
why?
wha
t ho
w?
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ADMdecisionNetwork
Worse, Decisions Are Heavily Related
Customer
objectives
Application Functional Conceptual Realization
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TORnetworkedIssues
Architecting is much more than Decomposition
Decomposition
is "easy"
Integration is
difficult
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LWAdecompositionAndIntegration
In Documentation Terms
system
subsystem subsystem subsystem �� � � � ���� ���� �� ���� �� �� � � � �
qualities e.g. performance
minutes 1 decision 1 decision 2 decision 3
minutes 2 decision 4 decision 5 decision 6
minutes k decision n decision n+1 decision n+2
's or structured
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ADMdocumentation
Revisiting Architecture
architecture decision
system
architect
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ADMpresentationIconArchitecture
Fundamental Question
emerging from
preconceived
creation context
environment
architecture
system
architect
decision = or
=
or
=
all
Is ?
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ADMarchitectureRevisited
The End
Back-up Slides and Answers only after this Slide
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Quantification from “The Role and Task of the System Architect”
driving views
shared issues
touched details
seen details
real-world facts
10
102
104
107
infinite
Quantityper year
(order-of-
magnitude)
architect
time per
item
100 h
1 h
10 min
meetings
consolidation
in
deliverables
informal
contacts
product details
sampling
scanning
0.1105
0.5
1 sec106
1010
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RSAdetailHierarchy
Quantification from “Architectural Thinking”
10 0
10 1
10 6
10 5
10 4
10 3
10 2
10 7
num
ber o
f de
tails
stre
tch
mon
o-
disc
iplin
ary
stre
tch
syst
em
stre
tch
subs
yste
m o
r fu
nctio
n
100 10 1
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ATmentalDynamicRange