© trygve reenskaug 2011ark2011 slide 1 01.10.2015 07:52 trygve reenskaug institutt for informatikk...

© Trygve Reenskaug 2011Ark2011 Slide 119.04.23 18:19

Trygve ReenskaugTrygve ReenskaugInstitutt for informatikkInstitutt for informatikkUniversitetet i OsloUniversitetet i Oslo

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

heim.ifi.uio.no/~trygver/themes/babyideheim.ifi.uio.no/~trygver/themes/babyide

The DCI Architecture: A New The DCI Architecture: A New Vision of Object-Oriented Vision of Object-Oriented ProgrammingProgramming


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Webster: ArcitectureWebster: Arcitecture

The art or science of building; specifically: the art or practice of designing and building structures and especially habitable ones


Our Hero: (End) UserOur Hero: (End) Userprogram execution creates valueprogram execution creates value

© Trygve Reenskaug 2011

The Direct Manipulation MetaphorThe Direct Manipulation Metaphor

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MVC MVC – Model View Controller– Model View Controller

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Object-OrientationObject-Orientation

In computer terms, Smalltalk is a recursion on the notion of computer itself. Instead of dividing “computer stuff” into things each less strong than the whole—like data structures, procedures, and functions which are the usual paraphernalia of programming languages—each Smalltalk object is a recursion on the entire possibilities of the computer.

Thus its semantics are a bit like having thousands and thousands of computer all hooked together by a very fast network.

Questions of concrete representation can thus be postponed almost indefinitely because we are mainly concerned that the computers behave appropriately, and are interested in particular strategies only if the results are off or come back too slowly.


A Rapidly ChangingA Rapidly ChangingNetwork of Communicating ObjectsNetwork of Communicating Objects


The Distributed OrganizationThe Distributed OrganizationAn Object Oriented ModelAn Object Oriented Model

ICCAS 1973


RestrictedOO: Object does the right thingRestrictedOO: Object does the right thingFullOO: System does the right thingFullOO: System does the right thing

RestrictedOO

1

Full OO

3

2

4

5Restricted

OORestricted

OORestricted

OO

1

Full OOFull OO

3

2

4

5


Bank

ToAccount

transfer (amount, fromAccount, toAccount)

FromAccount

transfer (amount,toAccount)

deposit (amount)

Customer

End User’s Mental ModelEnd User’s Mental Model What the system DOESWhat the system DOES


Use CasesUse CasesSeparation of Concern: IS and DOESSeparation of Concern: IS and DOES


Use CaseUse CaseExecuted in a ContextExecuted in a Context

Context-1

UseCase-1

UseCase-2

Context-2

BankTransfer

BankTransferContext

Role binding


Coplien, Bjørnvig: Lean ArchitectureCoplien, Bjørnvig: Lean ArchitectureISBN: 978-0-470-68420-7ISBN: 978-0-470-68420-7

Lean Principle:”everybody, all together, from early on.”

System architecture shall reflect the end user's mental model.

Architecture has two parts:What the system IS: Its stateWhat the system DOES: Its behavior

No wasteGet it right the first time!Be prepared for changes!


ConclusionConclusionDCI = Mental Model + Readable CodeDCI = Mental Model + Readable Code

The DCI paradigm:Work with system in different perspectives

• D ata Objects for what the system ISRestricted OO for domain information

• C ontext for the network of communicating objectsmarshal participating role-playing objects .

• I nteraction for what the system DOESdescribes runtime behavior


Combining Structure and Algorithm in a ClassCombining Structure and Algorithm in a Class

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Combining Structure and Algorithm in an ObjectCombining Structure and Algorithm in an Object

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Mapping Roles to ObjectsMapping Roles to Objects

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TraitsTraits

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If a role is an analysis concept (from the mind of the end user), then a trait is a general design concept that represents the role, and its implementation varies from programming language to programming language.


http://www.ifi.uio.no/~trygver mailto:

Useful Web resources:http://fullOO.infohttp://www.leansoftwarearchitecture.com/home/more-online-resourceshttp://www.gertrudandcope.com/thedciarchitecture

DCI project mailinglist:

Coplien, J.O., Bjørnvig, G; Lean Architecture for Agile Software Development; Wiley, Chichester, UK, 2010; ISBN 978-0-470-68420-7

Kay, Alan; The Early History of Smalltalk; Proceeding HOPL-II The second ACM SIGPLAN conference on History of programming languages; ACM New York, NY, USA 1993; ISBN:0-89791-570-4; doi>10.1145/154766.155364; http://www.smalltalk.org/smalltalk/TheEarlyHistoryOfSmalltalk_Introduction.html

Reenskaug, T; Wold, P.;, Lehne, O. A.: Working With Objects; Manning, Greenwich, CT 06830;1996; ISBN 1-884777-10-4; (Prentice Hall ISBN 0-13-452930-8). This book is out of print. An early .pdf version kan be downloaded free from [web page] http://folk.uio.no/trygver/1996/book/book11d.pdf

Wirfs-Brock, R.; McKean, A.; Object Design. Roles, Responsibilities, and Collaborations. ISBN 0‑201‑37943‑0; Addison-Wesley; Boston, MA, 2003.

Gamma et.al. (GOF) Design Patterns; ISBN 0-201-63361-; Addison-Wesley, Reading, MA. 1995.

More readingMore reading


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