DCI @ XING

DCI @ XING

hardwiring brainsBoris Tveritnev

XING Architecture at a glance

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Index

The problem

Problem by example

DCI

DCI and DDD

DCI and TDD

Application techniques

Takeaway

The

problem(s)Object Oriented Programming

http://donkeykong.wikia.com/wiki/User:CoolHungryYoshi?file=Donkey-kong-clean.gif

“I thought of objects being like biological cells and/or individual computers on a network, only able to communicatewith messages”

Alan Kay

http://userpage.fu-berlin.de/~ram/pub/pub_jf47ht81Ht/doc_kay_oop_en

Something went really wrong

• Simula (1967)

• Smalltalk (1980)

• C++ (1983)

• Java (1995)

• C# (2000)

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OOP as it is

•There is little in object orientation, that helps

the developer capture doing in the code

•One can’t reason about system behavior in

runtime

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https://s-media-cache-ak0.pinimg.com/736x/c2/02/1c/c2021c66544d3b66495d7d489f527405.jpg

“I made up the term 'object-oriented', and I

can tell you I didn't have C++ in mind”

Alan Kay

OOPSLA '97

Payments

domain@XING

http://www.kimberlywoodstucson.com/uploads/5/5/0/9/55094411/3783591_orig.png

Payments domain model

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ONLINE OFFLINE IN-APP

BONUS

B2B

customers

B2C

customers

Pay UsePayUsePay Pay Pay PayPay

More

Pay

MoreUse Bonus

Runtime vs design-time

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Runtime vs design-time

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Runtime vs design-time

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Data-Context-

InteractionHardwiring brains

http://1.bp.blogspot.com/_MyFAOEj9GKk/S-QmbuYk56I/AAAAAAAAAEQ/sHc-mwJBacc/s1600/left-brain-right-

brain.jpg

Users’ mental models

•What the system is

•What the system does

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Data (Records)

•Data objects express what the system is

•Methods and attributes that describe the data

• In essence they are just dumb DTOs

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http://vignette1.wikia.nocookie.net/uncyclopedia/images/3/3a/Pac_man_pie_chart.jpg

Data example

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Interaction (Roles)

•Roles describe the algorithms defining what

the system does

•Traits of objects

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Roles and Biz Processes

•Customer - Sales

•Debtor - Accounting

•Employer - BizDev

•SupportClient - Support

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https://ruthcatchen.files.wordpress.com/2012/03/artclass.jpg

Role example

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Context

•Specifies a network of communicating Objects

as interconnected Roles

•Represents a single Use Case

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Hide Client Context example

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Client Role example

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Role example

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Renew Contract Context example

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Contract Role example

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Client Role example

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DCI and DDDSwore friends

http://data.whicdn.com/images/67570097/original.gif

Aggregates

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•DDD defines Aggregate Root as an invariant

enforcing entry point

•DCI aids in finding correct aggregate

boundaries

http://petroloco.com/wp-content/uploads/2014/01/Disintegrating-01.jpg

Aggregate example

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Aggregate example

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Perfect match

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•DCI context implements a complete Use Case

•Domain events are results of executing a Use

Case

https://s-media-cache-ak0.pinimg.com/736x/7f/f3/7c/7ff37ca2c4d90a56064d0fc3d42ef58a.jpg

Domain events example

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Domain events example

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Common restrictions

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You need neither of them to build this

DCI and TDDRemoving the friction

http://i.dailymail.co.uk/i/pix/2013/02/23/article-2283273-1835CCED000005DC-212_634x438.jpg

Promoting BDD

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•Feature-driven top-down approach

•Structures the code and thought

http://www.codelanders.com/wp-content/uploads/2015/04/DDD_TDD_BDD_intersection.png

Zero-friction TDD

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•Allows to refactor inner parts without

constantly breaking tests

•With enough attention one can get pretty

close to executable specifications

http://icons.wunderground.com/data/wximagenew/l/ljranch/6.jpg

BDD example

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BDD example

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BDD example

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Application

techniquesDifferent ways in different languages

http://images2.fanpop.com/image/photos/9700000/Penguin-of-Death-penguins-of-madagascar-9714329-800-

600.gif

Libraries/Languages

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•C#: with Extension methods or dynamic

•Marvin: .Net CLI compatible language,

designed for DCI

•Ruby: with Method injection or using Maroon

•Javascript: hasOwnProperty and apply

•Java: Apache Zest (former Qi4J)

•Scala: traits

•C++: with Templates

Takeaway

http://personal.lse.ac.uk/robert49/ebooks/PhilSciAdventures/img/memory-brain.jpg

Win!

Touches key areas of agile process

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•Analysis with User Stories and Use Cases

•Customer can be closely involved in

discussions

•Embracing change separating stable domain

model from changing User Stories

•Aids in DDD application

•Promotes BDD

www.xing.com

Thank you

for your

attention!

Boris Tveritnev

More info

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1. http://www.artima.com/articles/dci_vision.html

2. DCI Glossary: http://folk.uio.no/trygver/2011/DCI-Glossary.pdf

3. http://fulloo.info/

4. https://groups.google.com/forum/#!forum/object-composition

5. Lean Architecture: for Agile Software Development, J. Coplien,

G. Bjørnvig, ISBN-13: 978-0470684207, Wiley, 2010.

6. A Personal Computer for Children of All Ages:

http://www.mprove.de/diplom/gui/Kay72a.pdf

7. Dr. Alan Kay on the Meaning of “Object-Oriented Programming”:

http://userpage.fu-

berlin.de/~ram/pub/pub_jf47ht81Ht/doc_kay_oop_en