Decremental Development @KevlinHenney Your customers do not buy - - PowerPoint PPT Presentation

Decremental

Development

@KevlinHenney

Your customers do not buy your software by the line.

David Evans

Remember that there is no code faster than no code.

Taligent's Guide to Designing Programs

Remember that there is no code cheaper to maintain than no code.

Remember that there is no code more secure than no code.

I have made this [letter] longer than usual because I have not had time to make it shorter.

Blaise Pascal

Je n'ai fait celle-ci plus longue que parce que je n'ai pas eu le loisir de la faire plus courte.

Blaise Pascal

I have made this [letter] longer than usual because I have not had time to make it shorter.

Blaise Pascal

time

I spent a lot of money on booze, birds and fast cars. The rest I just squandered.

George Best

speed

velocity

v = vx + vy

v = |v|

v = s t _

t s

t s

t s [T] [T]

utilisation

quality of estimation

Observe

Gather information from a range of sources

Orient

Understand where you're at and where you want to be

Decide

Develop a plan for action

Act

Carry out the plan

Boyd's OODA Loop

Decide

Develop a plan for action

Act

Carry out the plan

Observe

Gather information from a range of sources

Orient

Understand where you're at and where you want to be

Boyd's OODA Loop

Plan

Establish hypothesis, goal or work tasks

Do

Carry out the plan

Study

Review what has been done against plan (a.k.a. Check)

Act

Revise approach

• r artefacts based
• n study

Deming/Shewhart Cycle

The design process is an iterative one.

Andy Kinslow

A software system can best be designed if the testing is interlaced with the designing instead of being used after the design.

Alan Perlis

Plan

Establish hypothesis, goal or work tasks

Do

Carry out the plan

Study

Review what has been done against plan (a.k.a. Check)

Act

Revise approach

• r artefacts based
• n study

Deming/Shewhart Cycle

Write

Create or extend a test case for new behaviour — as it's new, the test fails

Reify

Implement so that the test passes

Reflect

Is there something in the code or tests that could be improved?

Refactor

Make it so!

Test-First Cycle

Why do cars have brakes?

Cars have brakes so you can slow down.

Cars have brakes so you can go fast.

code tests scripts

codified knowledge

knowledge acquisition

knowledge retention

learning

communication

social negotiation

model of participation

The biggest advantage of autonomously working teams is risk reduction through increased group intelligence.

Kevlin Henney

There’s little correlation between a group’s collective intelligence and the IQs of its individual members. But if a group includes more women, its collective intelligence rises.

"What Makes a Team Smarter? More Women"

Anita Woolley & Thomas W Malone http://hbr.org/2011/06/defend-your-research-what-makes-a-team-smarter-more-women/

The four conditions that characterize wise crowds: diversity of opinion, independence, decentralization, and aggregation.

size

scale

The first rule of scaling agile is… don't do it! Or rather, try to avoid it for as long as you possibly can.

Andreas Rowell

First Rule of Scaling Agile – DON'T!

https://www.linkedin.com/pulse/first-rule-scaling-agile-dont-andreas-rowell/

Software development does not have economies of scale. Development has diseconomies

• f scale.

Allan Kelly

Beyond Projects

http://www.slideshare.net/allankellynet/no-prokects-beyond-projects-refreshed-version

completion time for one person

𝑢 = 𝑢1

division of labour

𝑢 = 𝑢1 𝑜

𝑢 = 𝑢1 1 − 𝑞 𝑜 − 1 𝑜

portion in parallel Amdahl's law

communication

• verhead

(typical) connections (worst case)

𝑢 = 𝑢1 1 − 𝑞 𝑜 − 1 𝑜 + 𝑙 𝑜 𝑜 − 1 2

𝑢 = 𝑢1 1 − 𝑞 𝑜 − 1 𝑜 + 𝑙 𝑜 𝑜 − 1 2

t n

http://boingboing.net/2016/04/05/man-recreates-tsas-47400.html

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I have yet to see any problem, however complicated, which, when you looked at it in the right way, did not become still more complicated.

Anderson's Law

The Facebook iOS app has over 18,000 Objective-C classes, and in a single week 429 people contributing to it.

Facebook's code quality problem

Graham King

http://www.darkcoding.net/software/facebooks-code-quality-problem/

For every activity there is a certain appropriate scale.

Th The e bas asic ic thesis hesis [.. ...] .] is that hat

• rganiza

ganization tions s whi hich h design esign syst stems ems [.. ...] .] ar are e constrain nstrained ed to

• pr

produce

• duce designs

esigns whi hich h ar are e copie pies s

• f the

he communic municati ation

• n structu

ructures res

• f the

hese se organiza ganization tions. s.

Melvin vin Conw nway How Do Committees Invent?

We e ha have e seen een tha hat t this his fac act t ha has importan portant t implicatio plications ns for

• r the

he man anag ageme ement nt of syst stem em design. esign. [.. ...] .] A design esign ef effo fort rt should hould be e

• rganize

ganized d ac accord

• rding

ing to the he ne need ed for

• r communicatio

munication. n.

Melvin vin Conw nway How Do Committees Invent?

In referring to this as a ‘law,’ the appeal is to a force that will shape a system, much as a physical law, rather than as a rule that should be followed, as with the laws of a community or a state.

In this sense it is not a law that can be broken—the force is always there—only one that can be counterbalanced by other forces.

thrust drag lift gravity

design debt practice conway

We may therefore picture the process of form- making as the action of a series of subsystems, all interlinked, yet sufficiently free of one another to adjust independently in a feasible amount of time. It works, because the cycles of correction and recorrection, which occur during adaptation, are restricted to one subsystem at a time.

Christopher Alexander

Notes on the Synthesis of Form

Remove to improve