Love and death

© XPSurgery.com 2016 @kevinrutherford
Love and Death
“To love is to suffer. To avoid suffering
one must not love. But then one
suffers from not loving. Therefore,
to love is to suffer; not to love is to
suffer; to suffer is to suffer. To be
happy is to love. To be happy,
then, is to suffer, but suffering
makes one unhappy. Therefore,
to be unhappy, one must love or
love to suffer or suffer from too
much happiness.
I hope you're getting this down.”
Love and Death, Woody Allen, 1975

@kevinrutherford @xpsurgery
http://silkandspinach.net http://xpsurgery.com

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Extreme Normal Form:
1. Passes all tests
2. Expresses intent
3. No duplication
4. No extra stuff

Primitive Obsession
Feature Envy
Sim
ulated
Polym
orphism
Lazy Class
Temporary Field
Inappropriate
Intim
acy
ShotgunSurgery
Data Clump
Long
M
ethod
Large Class
???
??? ???
???
???
???
???
RefusedBequest

S ingle responsibility principle
O pen-closed principle
L iskov substitution principle
I nterface segregation principle
D ependency inversion principle

Principles of package cohesion
Reuse-release equivalence principle (REP)
Common-reuse principle (CRP)
Common-closure principle (CCP)
Principles of package coupling
Acyclic dependencies principle (ADP)
Stable-dependencies principle (SDP)
Stable-abstractions principle (SAP)

“This is Mrs Bencours,
one of my patients.
She thinks she's a sheep.”
Everything you always wanted to know about sex
but were afraid to ask, Woody Allen, 1975
coupling

Comparing Techniques by Means of Encapsulation
and Connascence,
Communications of the ACM Vol. 35, No. 9, Sept. 1992
pp. 147-151
Meilir
Page-Jones

1996
Meilir
Page-Jones

1999
Meilir
Page-Jones

Connascence between two software elements
A and B means either:
1) some change to A would require B to be changed, or
2) some change would require both A and B to be changed together
in order to preserve overall correctness.

Connascence between two software elements
A and B means either:
1) some change to A would require B to be changed,
(or at least carefully checked), or
2) some change would require both A and B to be changed together
in order to preserve overall correctness.

Meilir
Page-Jones
“I'll go so far as to say
that connascence [is]
at the heart of modern
software-engineering
constructs.”

2005-9
Grand Unified Theory
of Software Design
Jim
Weirich

Degree
Reach
Type

Degree
Type
Reach

Connascence of Name
int i = 9;
int j = Math.sqrt(i);
[static]

Connascence of Name
int i = 9;
int j = Math.sqrt(i);
N
N N
N
[static]

Connascence of Algorithm
get(...) put(...)
[static]

get(...) put(...)
A
[static]

get(...) put(...)
hash(...)
[static]

get(...) put(...)
hash(...)
A
[static]

Connascence of Position
printf(“%d %sn”, time.now(), request.path);
[static]

Connascence of Position
printf(“%d %sn”, time.now(), request.path);
P
[static]

Connascence of Convention
int basePrice = priceFor(sku); //  999 pence (== £9.99)
decimal salesTax = calcTax(basePrice);
return basePrice + salesTax;
[static]

Connascence of Convention
C
[static]

Connascence of Type
[static]

Connascence of Type
T
[static]

Static connascence:
Name Convention
Algorithm Type
Position (Difference)

string[] board = new string[12];
     :
     :
if (position[currentPlayer] > 11)
  index = 0;
Connascence of Value
[dynamic]

string[] board = new string[12];
     :
     :
if (position[currentPlayer] > 11)
  index = 0;
Connascence of Value
[dynamic]
V

email = Email.new()
email.setRecipient("foo@example.com")
email.setSender("me@mydomain.com")
email.setSubject("Hello World")
email.send()
Connascence of Execution
[dynamic]

email = Email.new()
email.send()
[dynamic]
E

email = Email.new()
email.send()
[dynamic]
E
E

Connascence of Identity
[dynamic]
fetch(`http://localhost:17174/salesmen/${salesmanId}`, {
  method: 'put',
  body: JSON.stringify({
    salesmanId: salesmanId,
    orderId: orderId,
    commission: commission
  })
})

Connascence of Identity
[dynamic]
fetch(`http://localhost:17174/salesmen/${salesmanId}`, {
  method: 'put',
  body: JSON.stringify({
    salesmanId: salesmanId,
    orderId: orderId,
    commission: commission
  })
}) I

Connascence of Timing
[dynamic]
xrayMachine.on()
Thread.sleep(20)
xrayMachine.off()

Connascence of Timing
[dynamic]
xrayMachine.on()
Thread.sleep(20)
xrayMachine.off()
T

Dynamic connascence:
Value Timing
Execution (Difference)
Identity

50
50
V = 2
E = 1

50
50
50
V = 3
E = 3

50
50
50
50
V = 4
E = 6

V = 5
E = 10
50
50
50
50
50

Type
Degree
Reach

expression ↔ expression 0
function ↔ function 1
object ↔ object 2
aggregate ↔ aggregate 3
process ↔ process 4

1. Minimize overall connascence
2. Minimize connascence crossing
encapsulation boundaries
By breaking the system into
encapsulated elements
By maximising the connascence
within encapsulation boundaries

1. Minimize overall connascence
By breaking the system into
encapsulated elements

Ca,b
= f(type, level, degree)
?

“I'll go so far as to say
that connascence [is]
at the heart of modern
software-engineering
constructs.”

Ca,b
= f(type, level, degree)

1. Break the monolith you have into
meaningful encapsulation units
2. Remove the “worst” connascence among
the encapsulation units
3. Find which encapsulation units have
the “most” internal connascence
4. Recurse into each, returning to the
top level after each one

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@kevinrutherford
@xpsurgery
http://silkandspinach.net/tag/connascence
http://xpsurgery.com

Love and death

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