DDD Dirty Harry style

Dirty Harry’sStyle

@ziobrando

giovedì 23 maggio 13

Goal #1

Domain-Driven Design NOT starting from scratch

Goal #2

Arrive to DDD in a non prescriptive fashion

Do you really need me?giovedì 23 maggio 13

Checkpoint

When to apply DDD?- Complex problem- High expectations

Anti-pattern

I want to do DDDI don’t know DDD well...

...so I apply DDD to a simple problem

I don’t see any advantage...DDD is useless.

We don’t learn in flatlandsgiovedì 23 maggio 13

That’s not our job

Call a Bomb Squadgiovedì 23 maggio 13

Our Safety Net

✓Environments

✓Build Scripts

✓Test suite

✓Private Database

✓Fixtures

✓Continuous Integration

✓...giovedì 23 maggio 13

Toolsgiovedì 23 maggio 13

Professionalsgiovedì 23 maggio 13

Proper Tools

Even in the worst situationsgiovedì 23 maggio 13

Could you please pass me

the ...thing?

The s5ngy one?

Yes, the one that looks

like ... that

Precision

Contraceptive

Aspirin

Language

avanscoperta

Checklist

Tools? --> Tool. (always the same)Precision? --> “When you are in state 12, the field MRKT_NFLD can be only B or K”Language? --> :-(

Application

ApplicationApplication

Application

Database

Application

Database

Application

Database

Application

Database

Application

Database

Application

Database

Data-based integrationgiovedì 23 maggio 13

avanscoperta

Data-‐based integra5on checklist

Can we tell...

Which application is responsible for the data structure?

Which requirement influenced data definition?

Is it still valid?

It it valid in my context?

Which applications use that data?

Which consequences if we alter the structure?

Goal #1

Arrive to DDD in a brownfield scenario

Solution #1

Put the mess aside and start form a greenfield scenario

Which problem do we want to

solve?

Onegiovedì 23 maggio 13

problemgiovedì 23 maggio 13

Our PROBLEM domain

past SOLUTIONS

Complexity

Our problem

Il nostro contesto

I nostri dati

I dati da condividere

Altro contesto

Il nostro database

Language!!

TRESPASSERS WILL BE SHOT

SURVIVORS WILL BE SHOT AGAIN

THIS DATABASE IS MY DATABASE

“Put in this way, it’s simple...”

DDD helps to solve complex problems,

DDD helps to solve complex problems, NOT to make simple problems complicated

Zombie management

strategies

A fence...giovedì 23 maggio 13

Learnt from the Romans

Romulus, let me run this query,

please...

Nope.Please,

Romulus ... it’s a read-‐only one

Bounded Context

Anti-Corruption Layer

getContattiUnici(…):List<Contatto>

<<Service>>ContactService

ContactService

context boundary

AttributoAttributo

<<Value Object>>Contatto

AttributoAttributo

<<Entity>>MyEntity

Our Context ACLcontext boundary

Componente

Other Context

ContactService

context boundary

AttributoAttributo

<<Entity>>MyEntity

Componente

Other Context

Model as it should be

ContactService

context boundary

AttributoAttributo

<<Entity>>MyEntity

Componente

Other Context

The legacy component with all its troubles

ContactService

context boundary

AttributoAttributo

<<Entity>>MyEntity

Componente

Other Context

The legacy component with all its troubles

Here we solve the mess, by any possible means.

...and within our Bounded Context...

The ideal modelgiovedì 23 maggio 13

It’s not that important...

Compliance

There’s no medal

But maybe...

http://www.youtube.com/watch?v=zDZFcDGpL4Ugiovedì 23 maggio 13

DDD as a learning process

DDD patterns support frequent

rewritingsgiovedì 23 maggio 13

DDD as an architecture that

supports evolution

...better provide us the right support

tool for design

Whiteboards

CRC Cards

“Can we really do this?”

“We need to put a valida9on layer to avoid incorrect data to enter into the system”

Really?

Complex

validation is a

(almost) same data

Different Behaviour

submitregisterPayment

amountcustomerstate

<<Entity>>Fattura

editvalidate

amountcustomer

<<Entity>>InvoicePreview

Multiple models

Frequent

Archetypes

3 archetypes?

Collaborative constructionTopic+Conversation

Facebook, Basecamp, Github

ExecutionState machines, Commands

TrackingLogging, Auditing, Datawarehouse, Events

Haven’t put “why do all my DDD

application looks the same” online, yet

What does the DBA say?

“I was expec9nd the DB structure to be defined once for all...”

My first idea...

She doesn’t exist in reality

Can a software component designed

before one application be adequate to N

following applications?giovedì 23 maggio 13

Obstaclesgiovedì 23 maggio 13

You have to watch your back

before interacting with system X

There are some f***ing stored

procedures that run every 10 minutes

Nobody knows exactly how do

they workgiovedì 23 maggio 13

Nobody knows exactly how do

they work

Nobody ever changed them and

came back alive

Risk...giovedì 23 maggio 13

Dress up properly before going

out! Are you wearing your T-‐

shirt?Lock the door when you get out!

Drive slowly!

Anxiety

Cognitive load

How many

things should

I know, before

touching the

can we be ignorant and

productive at the same time?

Transaction management?

Presentation Layer Application Layer Domain Layer Infrastructure Layer

99% of ex

sgiovedì 23 maggio 13

Repository & SRP

delivery()

pricecustomer

<<Entity>>Order

createOrder(…)delivery(order_ID, …)

<<Facade>>Application Facade

+saveChanges()

<<ORM>>Context

save(Order, Context)findById(id, Context)

<<Repository>>OrderRepository

createEmpty()

<<factory>>OrderFactory

opens / closes

creates

Infrastructure layer

Application LayerDomain Layer

Riceve il contesto transazionale dall'esternoIl Repository effettua le

operazioni di aggiunta e/o rimozione dal contesto, ma è l'application layer ad invocare saveChanges()

Crea il contesto e lo passa al repository

Do not

accept

candies

strangers

...why don’t we

set up a shared

database table?...

Ooops...

Do not

accept

candies

strangers

Do not accept candies

Motivationsgiovedì 23 maggio 13

Difficult childhood

namesurnamephoneNumber

Person

studentCardNumberStudent

subjectstatus

Professor

Show me you’re a

person...giovedì 23 maggio 13

...print yourself!

Difficult Childhood

namesurnamephoneNumber

Person

studentCardNumberStudent

subjectstatus

Professor

The two things do not match

...and it’s not an ORM problemgiovedì 23 maggio 13

Every architectural rule that starts with “every” is wrong

Consequencesgiovedì 23 maggio 13

You see, the worls is divided into two

categories: the one in a Bounded Context, and

the one who digs...

You ...dig!

Estimations

The tile layer

Accounting it right

Implementing amazing functionalities € 10.000

Accounting it right

Implementing amazing functionalities € 10.000Learning new techniques and tools € 4.000

Accounting it right

Establish Safety Conditions € 12.000

Accounting it right

Establish Safety Conditions € 12.000Cleaning up somebody else’s mess € 8.000

That will cost you an €xtra, sir...

Don’t forget to count the extra value also.

Estimations

Estimations“Explorative” evolutions

Legacy “Pandora’s box”giovedì 23 maggio 13

Ignorance based planning

100 1 2 3 4 5 6 7 8 9

Ignorance

Breakthrough

Ignorance

Gold plating?

Product Owner

A simple requirement

Product Owner

A simple requirement A simple requirement

Product Owner

Done as DDD prescribes

Product Owner

In a clean and elegant fashion

Product Owner

Soon ....ooops

Yes, but how can I understand if I am

doing DDD?

avanscoperta

Are we really doing DDD?

Result is better than expectationsNo fear in rewriting piecesWe’re having fun

Questions?

Really, you can...

Questions?

Really, you can...

Thank you

@ziobrandoalberto.brandolini@avanscoperta.it

DDD Dirty Harry style

Technology

DDD eXchange

The Need of Unmanned Systems DDD (Dull, Dirty, Dangerous ) Also –Distant Remote diagnoses, First Aid, Tele-Surgery, etc –Micro and nano devices Is well

Story of Lumbar Spine: page 1 of 13 2) When Things Fall Apart · Story of Lumbar Spine: 2) When Things Fall Apart DDD Post-Op DDD Post-Op DDD Post-Op DDD Post-Op DDD DDD

DDD is Superior to VVI? - circulationcirculation.or.kr/workshop/2007spring/file/DDD Pacemaker is... · What’s the Problem with DDD? DDD pacing forces the pacemaker to stimulate

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Dirty Harry — Main Title - PDXdrummer...Lalo Shifrin Dirty Harry OST Drums by John Guerin Transcription by Todd Bishop ã 45 x œœ x œœ xx œ > œ xx œ x œœ x œœ x œ x œ

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REVIEW Dirty Harry and the Real Constitution

DOWNTOWN DEVELOPMENT DISTRICT S (DDD)stateplanning.delaware.gov/ddd/documents/ddd-annual-report-2015.pdf · DDD Funds $164,068 $671,000 $4,806,137 $5,641,205 Private Investment Leverage

(Dirty Harry) Don Siegel (1971) - Inicio | Naullibres · 2021. 2. 8. · 10 2. Introducción Ningún film surge de la nada, y Harry el sucio (Dirty Harry, 1971), dirigido por Don

Dirty Harry Film Analysis

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DDD Dezinsekcija

Uwe Steinhoff Torture – The Case for Dirty Harry and

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Herausforderungen und Möglichkeiten mit psychisch ...€¦ · Mission Impossible; Armageddon; High Noon Dirty Harry; Der Pate; Ladykillers ... Befragung Psychiater Schweiz, 2016

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Joint Training for Open-domain Extraction on the Web · Gran Torino Walt Kowalski 2008 Dirty Harry Harry Callahan 1971 ... Agreement Term = Log Partition Log Partition of the Fused

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