Why do all my ddd apps look the same - Vienna 2014

Why do all my DDD apps look the same?

@ziobrando

About meIn the IT field since ZX Spectrum Generally in large scale projects (I might be biased) Freelance consultant: NotOnlyCode Trainer (Freelance & Skills MaDer) Technical Writer Blogger: h=p://ziobrando.blogspot.com TwiDer: @ziobrando

My e-‐mail: [email protected]

http://ziobrando.blogspot.com/

mailto:[email protected]

What I do

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Agile processesDomain-‐Driven DesignEfficiency & ManagementArchitectureFunny clown

Some things work pre=y well

Focusing on Core Domain

Core Domain

Core Domain

Nothing less than your best here.


Focusing on Core Domain Software Development as a Learning Process

Ignorance is the single greatest impediment

to throughput

Dan North

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Ignorance

This is when we make critical decisions

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IgnoranceBreakthrough

Can we anticipate this moment?

Is there any impediments to breakthroughs in the

way we develop soGware?

Hmm... let me think

Learning impediments

Time pressure --> estimations / expectations

Domain Experts availability / First Person experience

Learning Tools --> Discussion space, whiteboards, etc

Safety --> consequences of mistakes / Test env., etc.

Organization & Logistics --> noise, interruptions

Architecture

Food

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IgnoranceBreakthrough

Ignorance


Focusing on Core Domain Software Development as a Learning Process Explicit Bounded Context management

Establish a defensive perimeter

...and a fence

Know your bordersOur Bounded Context

Friendly BC

Pool

Promo

Campaign

...ACL

ACL

External Service Provider

...

ACL

APIData Exchange

Danger 1

Danger 2

obscure unnecessary complicated concept

Promozione

FilterCondition

Reward

Legacy Mess


Focusing on Core Domain Developing software as a learning process Explicit bounded context management Modeling the domain starting from Events

flow

EventEvent

Event

Event

Event

Domain Experts like Events

flow

EventEvent

Event

Event

Event


Command

Command

flow

EventEvent

Event

Event

Event


Command

Command

Command Event

But...

Why?

2 similar problems

STOP

Validation

We should prevent the user from entering incorrect data.

The Notorious Pub

hypothesis

Why doesn’t the police shut down this place?

Mother:

...

There’s a universe out there

Same data different behaviour

Before AGer

missing or inconsistent informaSon ModificaSons are possible DraG-‐like semanScs

all mandatory informaSon present No changes allowed Printed & Signed paper semanScs

DraG Contract

Deal

Source Executable

negoSaSon

finalize

sign off

compile

CartOrderPlan

CollaboraSve ConstrucSonMissingRoof

Warning

Comments & ConversaOon

Incomplete, growing artifact

...just like building soGware

The Deja-vu hypothesis

...not always

What if the domain expert is...

badly wrong

Boss:

Users must follow a prescripSve,

mandatory process

User:

The process as-‐is cannot be applied in

pracSce

Boss:

Users must follow a prescripSve,

mandatory process

Problem is...

© Alberto Brandolini -‐ 2008-‐2010

I’ve tried all this sh*t, man...

...and your idea doesn’t work...

Some problems have been solved well

in soGware development


Don’t push it too far...

but we’ve learnt something

How we thought we solved the

problem

R.I.P.

Maybe a be=er example...

Why don’t we just teach them to use github?

Cognitive load


They’re users, not hackers

too much cogniSve load

Integration strategies

Core Domain Strategy:

Simple enough to be included (in the domain) Good architectural integration UX Demanding (..?) ...increasing amount of generic requirements

Collaboration

Where’s the instrucSon manual?

UX Demanding

...pervasive changes in presentation layer user implicit expectations are high if it’s not beautiful & simple it won’t work

...remember we’re changing people’s behaviour

Conformist

(hopefully) better UI Lock-in (surrendering to zombies)

Our stuff

Big Collaboration Software

Zombies can be friendly aGer all...

Welcome�� in�� the�� world�� of�� plugin�� &�� customization

Separate Ways

lightweight links user cognitive load increased

Collaboration app

Our B.C.

Shared Kernel

Potentially reusable possibly overkill for generic subdomain unpredictable social consequences (the wizard)

Core domain

Collaboration

Domain-‐Specific commands

Domain-‐agnosSc primiSves


Yeah ...the problem’s sSll

open

...what about a White Russian?

From the UX expert

Need Help

Results -‐ Confidence -‐ Safety

Build Trust

(Having ideas != being right)

Experiment

be prepared to surprises (we are changing an ecosystem)

Measure

We’re both learning now...

Thank [email protected] hDp://ziobrando.blogspot.com

twiDer: ziobrando

mailto:[email protected]

http://ziobrando.blogspot.com