1. MVC and DCA: Two complimentary system architectures.
MVC and DCA: JavaZone 2006
Thursday, November 29, 2018
MVC and DCA: Two complimentary system architectures.
Trygve Reenskaug
Department of Informatics
University of Oslo
Java code at
MVC and DCA: JavaZone 2006
©2006 Trygve Reenskaug

2. The price of reliability is the pursuit of the utmost simplicity
The BabyUML Project
The essence of object orientation is that objects interact to accomplish some desired functionality.
The price of reliability is the pursuit of the utmost simplicity
(C.A.R. Hoare, 1980 Turing Award lecture)
BabyUML Goal:
Answer explicitly
What are the objects?
How are they interlinked?
How do they interact?
Do more – type less
MVC and DCA: JavaZone 2006

3. Model – View - Controller
MVC and DCA: JavaZone 2006
Thursday, November 29, 2018
Model – View - Controller
mental model
computer
data
Model
View bridges gap between
user Mental model and
Computer data
View
User
MVC and DCA: JavaZone 2006
©2006 Trygve Reenskaug

4. Model – View - Controller
MVC and DCA: JavaZone 2006
Thursday, November 29, 2018
Model – View - Controller
Controller creates and coordinates
multiple Views
View
Controller * 1
mental model
computer
data
Model
View bridges gap between
user Mental model and
Computer data
View
User
Run Demo
MVC and DCA: JavaZone 2006
©2006 Trygve Reenskaug

5. MVC and DCA: JavaZone 2006
Thursday, November 29, 2018
MVC Demo
MVC and DCA: JavaZone 2006
©2006 Trygve Reenskaug

6. The Anatomy of MVC Demo controller :Controller
MVC and DCA: JavaZone 2006
The Anatomy of MVC Demo
Thursday, November 29, 2018
controller
:Controller
panelView :DependencyPanel
:ActivityView
MVC and DCA: JavaZone 2006
©2006 Trygve Reenskaug

7. MVC example Synchronized Selection
MVC and DCA: JavaZone 2006
Thursday, November 29, 2018
MVC example Synchronized Selection
User
focusView
controller
activityView*
pointAndClickMouse
actionPerformed()
selectionChanged()
isSelected()
present
MVC and DCA: JavaZone 2006
©2006 Trygve Reenskaug

8. MVC example Synchronized Selection
MVC and DCA: JavaZone 2006
Thursday, November 29, 2018
MVC example Synchronized Selection
User
class Controller {
Activity selection;
inputView
controller
leafView*
public void actionPerformed (ActionEvent e) {
ActivityView source = (ActivityView) e.getSource();
selection = source.activity();
for (ActivityView view : activityViews) {
view.selectionChanged(); }
repaint();
pointAndClickMouse
actionPerformed()
selectionChanged()
isSelected()
public boolean isSelected (Activity act) {
return ( selection == act ); }
present
MVC and DCA: JavaZone 2006
©2006 Trygve Reenskaug

9. Model – View - Controller
MVC and DCA: JavaZone 2006

10. the Model as a single Object
illustration copied from The Java Tutorial Copyright Sun Microsystems, Inc.
methods (behavior)
derived attributes
owned attributes (state)
MVC and DCA: JavaZone 2006

11. the DCA Model Component Data + Collaboration + Algorithm
Algorithms
Collaborations
Data
activities
allocations
dependencies
resource
netBase
member Objects
(behavior)
(derived attributes) (external data view)
(owned attributes) (base data)
MVC and DCA: JavaZone 2006

12. DCA netBase – UML schema
predecessor
Activity
successor
Dependency
name
earlyStart
earlyFinish
duration
color *
Data
activities
allocations
dependencies
resource
netBase
DependencyPanel
DependencyPanel
GanttPanel
ResourcePanel
MVC and DCA: JavaZone 2006

13. Java as schema language
DCA netBase - Java
public class Activity { private Integer earlyStart, earlyFinish, duration; private String name; private Color color = Color.gray; ….
public class BabyBase extends Observable implements Observer {
private Set<Activity> activities;
private Set<MemberDependency> dependencies;
public class MemberDependency {
private Activity predecessor, successor; ...
Java as schema language
activities
allocations
dependencies
resource
netBase
Data (state)
MVC and DCA: JavaZone 2006

14. First DCA example DependencyPanel layout + collaboration
activities
allocations
dependencies
resource
Base
network Base
DependencyPanel
layout Algorithm (behavior)
GanttPanel
Collaboration (external data view)
Data (state)
ResourcePanel
MVC and DCA: JavaZone 2006

15. DCA ex.1: DependencyPanel responsible for layout Algorithm
layout Algorithm (behavior)
Model
private void addActivityViews() {
// Compute gridX, gridY, x0, y0, buttonExtent
for (int rank=0; rank <= rankedCollab.maxRank(); rank++) {
// compute xPos, yPos
for (Activity act : rankedCollab.activityListAtRank(rank)) {
ActivityView actView = new ActivityView(controller, act, 24) ;
add (actView);
yPos = yPos + gridY;
// misc. computations }
activities
allocations
dependencies
resource
Base
network Base
DependencyPanel
layout Algorithm (behavior)
GanttPanel
Collaboration (external data view)
Data (state)
ResourcePanel
MVC and DCA: JavaZone 2006

16. DCA ex.1: RankedCollab Query
Model
define activityListAtRank(Integer rank) as
select act
from activities act
where rank(act) = rank
activities
allocations
dependencies
resource
netBase
DependencyPanel
rankedCollab (external data view)
GanttPanel
Data (state)
ResourcePanel
MVC and DCA: JavaZone 2006

17. DCA ex.1: RankedCollab Java
Model
activities
allocations
dependencies
resource
netBase
public List<Activity> activityListAtRank (Integer rank) {
List<Activity> activityListAtRank
= new ArrayList<Activity>();
for (Activity act : bBase. allActivities()) {
if (rankOf(act) == rank) {
activityListAtRank.add(act); }
return activityListAtRank ;
DependencyPanel
layout Algorithm (behavior)
rankedCollab (external data view)
GanttPanel
Data (state)
ResourcePanel
MVC and DCA: JavaZone 2006

18. Second DCA example frontloading
Model
Compute earlyStart
activities
allocations
dependencies
resource
Base
network Base
Identify activity for frontloading
Compute earlyFinish
Algorithms (behavior)
Collaborations (external data views)
Data (state)
MVC and DCA: JavaZone 2006

19. DCA ex.2: frontloading query - frontloader
Model
activities
allocations
dependencies
resource
Base
network Base
define frontloader as
(select act
from Activities act
where act.earlyStart == null
and (for all pred in predecessors(act):
pred.earlyStart != null) ) someInstance
Algorithms (behavior)
DependencyPanell
GanttPanel
Collaborations (external data views)
BabyDataBase (state)
ResourcePanel
MVC and DCA: JavaZone 2006

20. DCA ex.2: frontloading Java - frontloader
Model
activities
allocations
dependencies
resource
Base
network Base
private boolean areAllDone(Set<Activity> actSet) {
boolean allPredsDone = true;
for ( Activity pred : actSet) {
if (pred.earlyStart() == null) {
allPredsDone = false;
break; }
return allPredsDone;
public Activity frontloader() {
for (Activity act : netBase.allActivities()) {
if (act.earlyStart() == null) {
Set<Activity> predSet = predecessorsOf(act);
if (areAllDone(predSet)) {
frontloader = act;
return (frontloader);
return null;
public Activity frontloader() {
for (Activity act : netBase.allActivities()) {
if (act.earlyStart() == null) {
Set<Activity> predSet = predecessorsOf(act);
if (areAllDone(predSet)) {
frontloader = act;
return (frontloader); }
return null;
private boolean areAllDone(Set<Activity> actSet) {
boolean allPredsDone = true;
for ( Activity pred : actSet) {
if (pred.earlyStart() == null) {
allPredsDone = false;
break;
return allPredsDone;
Algorithms (behavior)
DependencyPanell
GanttPanel
Collaborations (external data views)
BabyDataBase (state)
ResourcePanel
MVC and DCA: JavaZone 2006

21. DCA ex.2: frontloading frontload algorithm - Java
Model
public void frontload (Integer startWeek) {
Activity frontloader;
while ((frontloader = frontloadCollab.frontloader()) != null) {
Integer earlyStart = startWeek;
for (Activity pred : frontloadCollab.frontPredecessors()) {
earlyStart =
Math.max(earlyStart, pred.earlyFinish() + 1); }
frontloader.setEarlyStart(earlyStart);
activities
allocations
dependencies
resource
Base
network Base
Algorithms (behavior)
DependencyPanell
GanttPanel
Collaborations (external data views)
BabyDataBase (state)
ResourcePanel
MVC and DCA: JavaZone 2006

22. Second DCA example compute earlyFinish
Model
activities
allocations
dependencies
resource
Base
network Base
public Integer earlyFinish() {
if (earlyStart != null) {
return (earlyStart + duration – 1);
} else {
return null; }
Algorithms (behavior)
Collaborations (external data views)
Data (state)
MVC and DCA: JavaZone 2006

23. MVC – DCA Critique MVC separate Model and View DCA
when GUI and Model are deployed on different machine.
when the application code is complex.
write several View classes for the same Model class
when the user needs to see the Model from several perspectives.
write a Controller class to create and coordinate the Views
when the user needs to see them simultaneously.
DCA
simplify Data with a baby database
when the data structure is not obvious from the code.
separate out data queries in Collaboration classes
if Algorithms need to see data from different perspectives.
create a separate Algorithm class
if the Algorithm spans several member objects.
MVC and DCA: JavaZone 2006

24. The BabyUML Project Status
The essence of object orientation is that objects interact to accomplish some desired functionality.
The price of reliability is the pursuit of the utmost simplicity
(C.A.R. Hoare, 1980 Turing Award lecture)
BabyUML Goal:
Answer explicitly
What are the objects? Database schema
How are they interlinked? Collaboration
How do they interact? Algorithm
Do more – type less Remains to be done
MVC and DCA: JavaZone 2006

25. Java code and comments at
That’s all, thank you
Questions?
Java code and comments at
MVC and DCA: JavaZone 2006

26. More reading MVC and DCA: JavaZone 2006 Thursday, November 29, 2018
mailto: trygver ‘at’ ifi.uio.no
dca-demo example code:
Trygve Reenskaug: Original MVC notes from Xerox PARC
Charles Antony Richard Hoare: The Emperor's Old Clothes Turing Award lecture. Comm.ACM 24, 2 (Feb. 1981)
Trygve Reenskaug: The BabyUML discipline of programming (where A Program = Data + Communication + Algorithms). SoSym 5,1 (April 2006). DOI: /s x.
Unified Modeling Language: Superstructure. Version Object Management Group (OMG) document ptc/
Cattell, Barry: The Object Data Standard: ODMG Academic Press, London, ISBN
Erik Arisholm and Dag Sjøberg: A Controlled Experiment with Professionals to Evaluate the Effect of a Delegated versus Centralized Control …, Simula Research Laboratory Technical Report
Reenskaug, Wold, Lehne: Working With Objects. This book is out of print. A .pdf version kan be downloaded free from
Donald A. Norman: The Design of Everyday Things. Doubleday/Currency ISBN
MVC and DCA: JavaZone 2006
©2006 Trygve Reenskaug