This document summarizes a presentation by Dennis Traub on Domain-Driven Design (DDD). It discusses key DDD concepts like the ubiquitous language, bounded contexts, subdomains and core domains. It provides an example of applying these concepts to an ambulance flight management system. It also discusses architectural approaches to applying DDD like separating domains, applications services and interfaces. The presentation emphasizes that DDD is about modeling the business domain and separating concerns, not about diagrams or class modeling. It is about applying object-oriented principles at the architectural level.

1. Dennis Traub @dtraub
strategic application development with
Domain-Driven Design
dotnet Cologne 2013 – 03. Mai 2013 – #dnc13

2. Dennis Traub @dtraub
Now, who‘s that guy?
Dennis Traub
Founder, Owner, CEO, Single Employee of
D. Traub Software Development Consultancy
@dtraub
Consultant, developer, trainer, speaker
39 years old
Married, father of one

3. Dennis Traub @dtraub
51
Blue Book
Actually it should
be two books!
Terminology
The Ubiquitous Language
2
An Example
Bounded Contexts
and Subdomains
3
Lasagna
… the new Spaghetti?
4
End
Questions & Answers
AGENDA

4. Dennis Traub @dtraub
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The „Blue Book“ by Eric Evans

5. Dennis Traub @dtraub
• Entities
• Value Objects
• Aggregates
• Repositories
• Services
• Factories
• etc.
The „Blue Book“ by Eric Evans
Tactical
Class
Design
• Model Integrity
• Large-Scale Structure
• Bounded Contexts
• Core Domain
• Context Maps
• Ubiquitous Language
• etc.
Strategic
DDD
It should be two books!

6. Dennis Traub @dtraub
Domain

7. Dennis Traub @dtraub
a sphere of
knowledge, influence, or activity

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what an organization does
and the world it does it in

9. Dennis Traub @dtraub
Domain Model

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a system of abstractions that describes
selected aspects of a domain

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can be used to solve problems
related to that domain

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don‘t model reality

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we model useful abstractions of reality

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Ubiquitous Language

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a language structured around
the domain model

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used by all team members

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Bounded Context

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an explicit boundary within which
a domain model exists

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inside the boundary
all terms have specific meaning

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these terms are part of the context‘s
ubiquitous language

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Subdomains

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the whole domain of the organization
is comprised of subdomains

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they focus on only one
specific area of the whole business domain

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Core Domain

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the distinctive part of the model,
central to the users‘ goals

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differentiates the application and
makes it valuable

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the most important subdomain

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Example:

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Ambulance Flight Management
order flights from an operator
dispatch patients
assign medical staff

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Bounded Contexts
1 Patiententransport-Disposition
2 Flugplanung und -durchführung
3 Personaleinsatzplanung (Flugärzte, Rettungsassistenten)
4 Stammdaten, Rechnungswesen
5 Benutzerrechte, Web-Oberfläche

31. Dennis Traub @dtraub
Subdomains
6 Bodentransport
7 Abrechnung, Buchhaltung
8 Anwendungsoberfläche
9 REST-Schnittstelle
10 Benutzer- und Zugriffsrechte
1 Ambulanzflug-Disposition
2 Flottenmanagement
3 Flugplanung
4 Passagier-/Patientendaten
5 Medizinisches Personal

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remember, we don‘t build a model that
works for everyone

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to focus our effort and resources we ask
two questions for each subdomain

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how complex is it?
1

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what‘s the value to our specific problem?
(if we model it ourselves)
2

36. Dennis Traub @dtraub
Core Domain
6 Bodentransport
7 Abrechnung, Buchhaltung
8 Anwendungsoberfläche
9 REST-Schnittstelle
10 Benutzer- und Zugriffsrechte
1 Ambulanzflug-Disposition
2 Flottenmanagement
3 Flugplanung
4 Passagier-/Patientendaten
5 Medizinisches Personal
Ambulanzflug-Disposition

37. Dennis Traub @dtraub
we don‘t use DDD
when there is no value in
formalizing the problem
the tactical Building Blocks

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we only use DDD in parts
where we get a competitive
advantage

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Best Practice
Architecture

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DAL / O/R-Mapper
Domain / Business Model / BLL
Presentation Layer
Application Services
Infrastructure
CommonServices

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WCFData Access
UI
Business Logic
I/O

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Lasagna is the new Spaghetti

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UI Data Access
Domain Model
Application Services
I/OWCF Tests

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the D in SOLID
DependencyInversion Principle (just in case)

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UI Data Access
Domain Model
Application Services
I/OWCF Tests

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Source: Growing Object-OrientedSoftware, Guided by Tests -- Freeman & Pryce
Simple
Testable
Flexible

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Onion Architecture
Hexagonal Architecture
Ports & AdaptersArchitecture

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Summary

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DDD != Silver Bullet

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DDD != Diagrams

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DDD != Class Modeling

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DDD == how the business works

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DDD == Separation of Concerns

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DDD is basically the application of
the SOLID principles of object-orientation
on an architectural level

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The „Blue Book“ by Eric Evans

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Another essential Book

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And another one

58. Dennis Traub @dtraub
THANK YOU!
@dtraub – #dnc13