A talk I presented at vNext Orange County, 25th of February 2013 about the importance of delivering business value and how you as a developer can much easier meet the requirements of the end user by applying practices like DDD and utilizing things like CQRS and MVVM to help decouple your software and focus better.

2. Lets focus on business value
Power point template by
Colin Eberhardt

3. Agenda
How to focus on business value
Domain Driven Design
Concrete patterns; CQRS, MVVM
Bifrost – an open-source framework to cover it all

4. Who am I
Einar Ingebrigtsen
@einari einar@dolittle.com
http_//www.dolittle.com
http://blog.dolittle.com
http://www.ingebrigtsen.info

5. Statistics
Software projects
2009:
- 32% successful
- 24% failed
- 44% challenged
2004:
- Cancelled projects cost $55 Billion Annually
http://www.projectsmart.co.uk/docs/chaos-report.pdf

6. Statistics
http://www.typemock.com/blog/2012/07/18/the-severity-of-bugs-are-we-doomed/

7. What are we getting paid to do?
Use the most fancy technology out there
C# 5.0, Roslyn, F#, TPL, ASP.net MVC 3,
SignalR, RavenDB
Join the alpha geek crew and use all the
latest buzz words and create an architecture
around that showcase our technical skills?

8. What is business value?
The short answer
Helping the business achieve its
objectives
Faster Simpler Cheaper Better More

9. Why is this hard to do?
Developers don’t understand what the
business needs
The Business doesn’t understand what the
business needs

10. Why is this hard to do?
Even if we do understand what they want,
we can’t build it because of ...
Race Eager
conditions
Transactions Logging Serialization Performance
loading
Lazy
Caching Mapping Auditing Concurrency Staleness
loading

11. Why is this hard to do?
If somehow we’ve managed to get our
infrastructure in place and give the business
what it needs, it’s TOO LATE!
Legal New Market
Changes Priorities Changes
New New
Acquisitions
Requirements Competitor

12. Be agile!
Not just in terms of process
(Scrum, Kanban, XP)
We need to be able to change
decisions
priorities
CODE!!

13. Understand who your user is

14. Feedback loop
Talk to users regularly
Test
TDD / BDD
Executable Specifications
Testers

15. Please fail!
Fail regularly and fail fast
Be Agile and really iterate
Be honest!

16. Domain Driven Design
Focus on the core domain
Creative collaboration between domain
experts and software practitioners
Create a common language and common
understanding of the domain

17. Domain Driven Design
Building blocks
Aggregate Roots
Value Objects
Services
Repositories
Entities
… and more…

18. Bounded Contexts
Different representations in different
contexts

19. Bounded Contexts - Shopping

20. Bounded Contexts – Shift Management
Employee
Plays a central role – identified by Social Security
Number
Substitute
It refers to the Employee by concept, but we do
not need its address – only its availability and
possibly its name for display purposes

21. Decoupling
Application Level
Make many applications
Unit Level
Interchangeable components
New Code
Velocity

22. The opposite of decoupling
DRY – Don’t Repeat Yourself
Use of concrete implementations

23. Single Responsibility Principle
Types represent one thing
Methods do only one thing
Be fine grained and clear
Easier to name

24. CQRS
Client
Command
Queries
Domain Event Handlers
Publish
Persist Update
Domain Persistence Read Model

25. Command
Expresses what should happen
Should express intent
AddItem- / AddAccessory- ToCart - maps to
AddProduct() on the AggregateRoot

26. EventSource
The source of events
The place that events originate from

27. Aggregate Root
Holds only internal state, if needed - no
public state
Exposes behavior as methods

28. Event
Represents the truth in the system; “... this
is what happened...”
Simple DTO with primitive properties only!

29. MVVM
Model Get from server
View
Observes
Observable
ViewModel

30. bifrost

31. Bifrost
Full end to end framework for line-of-
business application development
Promotes good practices such as CQRS,
MVVM through high focus on DDD
You don’t need the entire thing, but will get
benefits for every component you add

32. Bifrost
Our motivation
A platform for us to build LOB applications on
Make us focus on delivering business value
Easy to use, hard to use wrong
“It just works!”

33. Bifrost
Client focus
JavaScript
ASP.net
Single Page Applications
Web in general
Silverlight
WinRT (Experimental)

34. Bifrost
Backend
CQRS
Cloud scale
Realtime applications
Clients persistently connected to the server

35. Bifrost - Architecture
Client
Result that affect
Queries and Invoke Behavior Results /
Read Models Meta Data
Server
Queries Domain
Read Models Meta Data

36. CQRS – Bifrost Style
Client
Command
Command
Coordinator
Command
Handler(s)
Aggregate Root
Read Model Event Subscriber(s) Events
EventStore

38. User story
Persona: Hannah
Works with human resources, she is responsible
for hiring of permanent employees but also for
finding substitutes when people are on sick
leaves
As Hannah I need to be able to quickly
register any employees coming in before we
got all the details about the person

39. User story
Requirements
First Name - Required
Last Name - Required
Social Security Number – Required
This is what identifies a person uniquely

40. Where are we??
Client
Model View ViewModel
Command
Command
Handler(s)
Aggregate Root
Read Model Event Subscriber(s) Events
EventStore

41. Bifrost – What did we solve?
Decoupling
Commands representing the behavior
Events are the contract
Read and behavior are two different things
Working in parallel
Making it easier to apply agile principles

42. Bifrost - Roadmap
Realtime applications
Clients persistently connected to the server
Refine client model
Formalizations
Bounded Context, Modules …
Simplifications
Scale out options
Redis, Azure ++

43. Getting started

45. Summary
Domain Driven Design
Will help you establish a language and understand what you’re creating
CQRS
Lets you establish a set of good patterns and practices, mind opener
Bifrost
One incarnation – but not look at it as a CQRS implementation, it is so much more
Please rate the talk at
http://tinyurl.com/BusinessValue2
http://blog.dolittle.com http://bifrost.dolittle.com

46. Thanks for your
attention