Presentation by Sebastián González of the paper "Context Traits: Dynamic Behaviour Adaptation Through Run-Time Trait Recomposition" at the Modularity • AOSD 2013 conference.

1. Dynamic Behaviour Adaptation
Through Run-Time Trait Recomposition
Sebastián González
Kim Mens
Marius Colacioiu
Walter Cazzola
29 March 2013
Modularity AOSD 2013
UCLouvain . U. Milan
Context Traits

2. Towards a Mindset Shift 2
programming in isolation programming with context
forward!
?
?
?
?
?
?

3. Towards a Mindset Shift 2
Caution
Design patterns
Plugin architectures
Conditional statements
...
programming in isolation programming with context
forward!
?
?
?
?
?
?

4. m(a) {
if ( ) { IE logic }
!
else if ( ) { Opera logic }
else if ( ) { Chrome logic }
else if ( ) { Safari logic }
else if ( ) { Firefox logic }
else { default logic }
}
Conditional Statements 3
Some variant of ...

5. m(a) {
if ( ) { IE logic }
!
else if ( ) { Opera logic }
else if ( ) { Chrome logic }
else if ( ) { Safari logic }
else if ( ) { Firefox logic }
else { default logic }
}
Conditional Statements 3
Some variant of ...
Adaptable

6. m(a) {
if ( ) { IE logic }
!
else if ( ) { Opera logic }
else if ( ) { Chrome logic }
else if ( ) { Safari logic }
else if ( ) { Firefox logic }
else { default logic }
}
Conditional Statements 3
Some variant of ...
Adaptable
Tangled
Scattered
Fixed
No reuse
Complex logic

7. Design Patterns 4
m(a) { Firefox strategy }
m(a) { default strategy }
m(a) {
strategy.m(a)
}
m(a) { IE strategy }
m(a) { Opera strategy }
m(a) { Chrome strategy }
m(a) { Safari strategy }

8. Design Patterns 4
m(a) { Firefox strategy }
m(a) { default strategy }
m(a) {
strategy.m(a)
}
m(a) { IE strategy }
m(a) { Opera strategy }
m(a) { Chrome strategy }
m(a) { Safari strategy }
strategy

9. Design Patterns 4
m(a) { Firefox strategy }
m(a) { default strategy }
m(a) {
strategy.m(a)
}
m(a) { IE strategy }
m(a) { Opera strategy }
m(a) { Chrome strategy }
m(a) { Safari strategy }
strategy

10. Design Patterns 4
m(a) { Firefox strategy }
m(a) { default strategy }
m(a) {
strategy.m(a)
}
m(a) { IE strategy }
m(a) { Opera strategy }
m(a) { Chrome strategy }
m(a) { Safari strategy }
strategy

11. Design Patterns 4
m(a) { Firefox strategy }
m(a) { default strategy }
m(a) {
strategy.m(a)
}
m(a) { IE strategy }
m(a) { Opera strategy }
m(a) { Chrome strategy }
m(a) { Safari strategy }
strategy
Modular
Open

12. Design Patterns 4
m(a) { Firefox strategy }
m(a) { default strategy }
m(a) {
strategy.m(a)
}
m(a) { IE strategy }
m(a) { Opera strategy }
m(a) { Chrome strategy }
m(a) { Safari strategy }
strategy
Infrastructural burden
Anticipated adaptation points
Modular
Open

13. Layer-Based COP 5
Later on...

14. In The Paper
‣ Contexts
‣ Traits
‣ Context-Driven Trait Compositions
‣ Composition Policies
‣ Behaviour Extensibility
‣ Context Traits in JavaScript
‣ Implementation Notes
‣ Case Studies
‣ Related Work
‣ Future Work
6

15. ‣ Contexts
‣ Traits
‣ Context-Driven Trait Compositions
‣ Composition Policies
‣ Behaviour Extensibility
‣ Context Traits in JavaScript
In This Presentation 7

16. Contexts as Situation Reifiers 8
computationally
accessible data
Battery charge = 220 mAh
Idle cycles = 100 MHz
User agent = “Mozilla/5.0...”
Z axis = 0.03

17. Contexts as Situation Reifiers 8
computationally
accessible data
no semantics
Battery charge = 220 mAh
Idle cycles = 100 MHz
User agent = “Mozilla/5.0...”
Z axis = 0.03

18. Contexts as Situation Reifiers 8
computationally
accessible data
no semantics
Battery charge = 220 mAh
Idle cycles = 100 MHz
User agent = “Mozilla/5.0...”
Z axis = 0.03
action can be taken
well-defined
situations
Context
Discovery
Low battery charge
High CPU load
Firefox
Landscape orientation

19. Contexts as Situation Reifiers 8
computationally
accessible data
no semantics
Battery charge = 220 mAh
Idle cycles = 100 MHz
User agent = “Mozilla/5.0...”
Z axis = 0.03
action can be taken
well-defined
situations
Context
Discovery
contexts are reified situations
for which adapted application behaviour can be defined
Low battery charge
High CPU load
Firefox
Landscape orientation

20. Contexts as Situation Reifiers 8
computationally
accessible data
no semantics
Battery charge = 220 mAh
Idle cycles = 100 MHz
User agent = “Mozilla/5.0...”
Z axis = 0.03
action can be taken
well-defined
situations
Context
Discovery
contexts are reified situations
for which adapted application behaviour can be defined
Low battery charge
High CPU load
Firefox
Landscape orientation
LowBattery = new Context();
window.addEventListener(‘batterystatus’,
function (data) {
if (data.level < 30)
LowBattery.activate();
else
LowBattery.deactivate(); });
... in JavaScript

21. T.TagT.Tag
tagName
addAttribute
getAttribute
setAttribute
removeAttribute
forEachAttribute
T.NodeT.Node
content
parent
appendChild
replaceChild
removeChild
walkChildren
Traits as Basic Behavioural Units 9
tag a1=”v1” a2=”v2”
T.ElementT.Element
elementsByTagName
elementsByAttribute
getAttribute
setAttribute
walkChildren

22. T.TagT.Tag
tagName
addAttribute
getAttribute
setAttribute
removeAttribute
forEachAttribute
T.NodeT.Node
content
parent
appendChild
replaceChild
removeChild
walkChildren
Traits as Basic Behavioural Units 9
tag a1=”v1” a2=”v2”
T.ElementT.Element
elementsByTagName
elementsByAttribute
getAttribute
setAttribute
walkChildren
provided
methods

23. T.TagT.Tag
tagName
addAttribute
getAttribute
setAttribute
removeAttribute
forEachAttribute
T.NodeT.Node
content
parent
appendChild
replaceChild
removeChild
walkChildren
Traits as Basic Behavioural Units 9
tag a1=”v1” a2=”v2”
T.ElementT.Element
elementsByTagName
elementsByAttribute
getAttribute
setAttribute
walkChildren
required
methods

24. T.TagT.Tag
tagName
addAttribute
getAttribute
setAttribute
removeAttribute
forEachAttribute
T.NodeT.Node
content
parent
appendChild
replaceChild
removeChild
walkChildren
Traits as Basic Behavioural Units 9
+
+
tag a1=”v1” a2=”v2”
T.ElementT.Element
elementsByTagName
elementsByAttribute
getAttribute
setAttribute
walkChildren
sum
operator

25. T.TagT.Tag
tagName
addAttribute
getAttribute
setAttribute
removeAttribute
forEachAttribute
T.NodeT.Node
content
parent
appendChild
replaceChild
removeChild
walkChildren
XML.ElementXML.Element
tagName
addAttribute
getAttribute
setAttribute
removeAttribute
forEachAttribute
content
parent
appendChild
replaceChild
removeChild
walkChildren
id
elementsByTagName
elementsByAttribute
Traits as Basic Behavioural Units 9
+
+
tag a1=”v1” a2=”v2”
T.ElementT.Element
elementsByTagName
elementsByAttribute
getAttribute
setAttribute
walkChildren
=

26. T.TagT.Tag
tagName
addAttribute
getAttribute
setAttribute
removeAttribute
forEachAttribute
T.NodeT.Node
content
parent
appendChild
replaceChild
removeChild
walkChildren
XML.ElementXML.Element
tagName
addAttribute
getAttribute
setAttribute
removeAttribute
forEachAttribute
content
parent
appendChild
replaceChild
removeChild
walkChildren
id
elementsByTagName
elementsByAttribute
Traits as Basic Behavioural Units 9
+
+
tag a1=”v1” a2=”v2”
T.ElementT.Element
elementsByTagName
elementsByAttribute
getAttribute
setAttribute
walkChildren
=

27. T.TagT.Tag
tagName
addAttribute
getAttribute
setAttribute
removeAttribute
forEachAttribute
T.NodeT.Node
content
parent
appendChild
replaceChild
removeChild
walkChildren
XML.ElementXML.Element
tagName
addAttribute
getAttribute
setAttribute
removeAttribute
forEachAttribute
content
parent
appendChild
replaceChild
removeChild
walkChildren
id
elementsByTagName
elementsByAttribute
Traits as Basic Behavioural Units 9
+
+
tag a1=”v1” a2=”v2”
T.ElementT.Element
elementsByTagName
elementsByAttribute
getAttribute
setAttribute
walkChildren
T[“Element”] =
Trait({
elementsByTagName: function(name) { ... },
elementsByAttribute: function(attr) { ... },
getAttribute: Trait.required,
setAttribute: Trait.required,
walkChildren: Trait.required });
... in JavaScript
=

28. T.TagT.Tag
tagName
addAttribute
getAttribute
setAttribute
removeAttribute
forEachAttribute
T.NodeT.Node
content
parent
appendChild
replaceChild
removeChild
walkChildren
XML.ElementXML.Element
tagName
addAttribute
getAttribute
setAttribute
removeAttribute
forEachAttribute
content
parent
appendChild
replaceChild
removeChild
walkChildren
id
elementsByTagName
elementsByAttribute
Traits as Basic Behavioural Units 9
+
+
tag a1=”v1” a2=”v2”
T.ElementT.Element
elementsByTagName
elementsByAttribute
getAttribute
setAttribute
walkChildren
T[“Element”] =
Trait({
elementsByTagName: function(name) { ... },
elementsByAttribute: function(attr) { ... },
getAttribute: Trait.required,
setAttribute: Trait.required,
walkChildren: Trait.required });
... in JavaScript
=
traits.js [ Van Cutsem &
Miller 2011 ]

29. T.TagT.Tag
tagName
addAttribute
getAttribute
setAttribute
removeAttribute
forEachAttribute
T.NodeT.Node
content
parent
appendChild
replaceChild
removeChild
walkChildren
XML.ElementXML.Element
tagName
addAttribute
getAttribute
setAttribute
removeAttribute
forEachAttribute
content
parent
appendChild
replaceChild
removeChild
walkChildren
id
elementsByTagName
elementsByAttribute
Traits as Basic Behavioural Units 9
+
+
tag a1=”v1” a2=”v2”
T.ElementT.Element
elementsByTagName
elementsByAttribute
getAttribute
setAttribute
walkChildren
T[“Element”] =
Trait({
elementsByTagName: function(name) { ... },
elementsByAttribute: function(attr) { ... },
getAttribute: Trait.required,
setAttribute: Trait.required,
walkChildren: Trait.required });
... in JavaScript
=

30. T.TagT.Tag
tagName
addAttribute
getAttribute
setAttribute
removeAttribute
forEachAttribute
T.NodeT.Node
content
parent
appendChild
replaceChild
removeChild
walkChildren
XML.ElementXML.Element
tagName
addAttribute
getAttribute
setAttribute
removeAttribute
forEachAttribute
content
parent
appendChild
replaceChild
removeChild
walkChildren
id
elementsByTagName
elementsByAttribute
Traits as Basic Behavioural Units 9
+
+
tag a1=”v1” a2=”v2”
T.ElementT.Element
elementsByTagName
elementsByAttribute
getAttribute
setAttribute
walkChildren
T[“Element”] =
Trait({
elementsByTagName: function(name) { ... },
elementsByAttribute: function(attr) { ... },
getAttribute: Trait.required,
setAttribute: Trait.required,
walkChildren: Trait.required });
... in JavaScript
=

31. Traits as Basic Behavioural Units 9
+
+
tag a1=”v1” a2=”v2”
T.ElementT.Element
elementsByTagName
elementsByAttribute
getAttribute
setAttribute
walkChildren
T[“Element”] =
Trait({
elementsByTagName: function(name) { ... },
elementsByAttribute: function(attr) { ... },
getAttribute: Trait.required,
setAttribute: Trait.required,
walkChildren: Trait.required });
... in JavaScript
=
T.Tag
tagName
addAttribute
getAttribute
setAttribute
removeAttribute
forEachAttribute
T.Node
content
parent
appendChild
replaceChild
removeChild
walkChildren
XML.Element
tagName
addAttribute
getAttribute
setAttribute
removeAttribute
forEachAttribute
content
parent
appendChild
replaceChild
removeChild
walkChildren
id
elementsByTagName
elementsByAttribute

32. Default Behaviour & Context 10
HTML.Element
addAttribute
getAttribute
...
style
title
T.HTML.ElementT.HTML.Element
class
style
title
getAttribute
setAttribute
= XML.Element +

33. = HTML.Element +
HTML.Anchor
addAttribute
...
href
type
target
T.HTML.AnchorT.HTML.Anchor
href
type
target
getAttribute
setAttribute
Default Behaviour & Context 10
HTML.Element
addAttribute
getAttribute
...
style
title
T.HTML.ElementT.HTML.Element
class
style
title
getAttribute
setAttribute
= XML.Element +

34. = HTML.Element +
HTML.Anchor
addAttribute
...
href
type
target
T.HTML.AnchorT.HTML.Anchor
href
type
target
getAttribute
setAttribute
Default Behaviour & Context 10
HTML.Element
addAttribute
getAttribute
...
style
title
T.HTML.ElementT.HTML.Element
class
style
title
getAttribute
setAttribute
= XML.Element +
HTML[“Element”] =
Trait.compose(XML.Element, T.HTML.Element);
HTML[“Anchor”] =
Trait.compose(HTML.Element, T.HTML.Anchor);
... in JavaScript

35. = HTML.Element +
HTML.Anchor
addAttribute
...
href
type
target
T.HTML.AnchorT.HTML.Anchor
href
type
target
getAttribute
setAttribute
Default Behaviour & Context 10
Default
... for prototypical situations
Prototypical behaviour ...
HTML.Element
addAttribute
getAttribute
...
style
title
T.HTML.ElementT.HTML.Element
class
style
title
getAttribute
setAttribute
= XML.Element +
( unperturbed system )
HTML[“Element”] =
Trait.compose(XML.Element, T.HTML.Element);
HTML[“Anchor”] =
Trait.compose(HTML.Element, T.HTML.Anchor);
... in JavaScript

36. Context + Traits 11
... in JavaScriptContext Traits
let Default ∈ C Default = new Context();

37. Context + Traits 11
... in JavaScriptContext Traits
let Default ∈ C Default = new Context();
a = new HTML.Anchor();let ida ∈ L

38. Context + Traits 11
... in JavaScriptContext Traits
let Default ∈ C Default = new Context();
a = new HTML.Anchor();let ida ∈ L
constitution: L ⨉ C → T

39. W3Clet W3C ∈ C W3C = new Context();
Context + Traits 11
... in JavaScriptContext Traits
let Default ∈ C Default = new Context();
a = new HTML.Anchor();let ida ∈ L
constitution: L ⨉ C → T

40. W3Clet W3C ∈ C W3C = new Context();
Context + Traits 11
... in JavaScriptContext Traits
let Default ∈ C Default = new Context();
a = new HTML.Anchor();let ida ∈ L
constitution: L ⨉ C → T

41. W3Clet W3C ∈ C W3C = new Context();
Context + Traits 11
... in JavaScriptContext Traits
let Default ∈ C Default = new Context();
a = new HTML.Anchor();let ida ∈ L
constitution: L ⨉ C → T

42. W3Clet W3C ∈ C W3C = new Context();
Context + Traits 11
... in JavaScriptContext Traits
let Default ∈ C Default = new Context();
a = new HTML.Anchor();let ida ∈ L
constitution: L ⨉ C → T
constitution( ida, W3C ) = W3C.adapt(a, T.ValidAnchor);
T.ValidAnchorT.ValidAnchor
addAttribute
setAttribute
removeAttribute
parent
...

43. W3Clet W3C ∈ C W3C = new Context();
Context + Traits 11
... in JavaScriptContext Traits
Untrusted
let Default ∈ C Default = new Context();
a = new HTML.Anchor();let ida ∈ L
constitution: L ⨉ C → T
constitution( ida, W3C ) = W3C.adapt(a, T.ValidAnchor);
let Untrusted ∈ C Untrusted = new Context();
T.ValidAnchorT.ValidAnchor
addAttribute
setAttribute
removeAttribute
parent
...

44. W3C
constitution
( ida, Untrusted ) =
Untrusted.adapt
(a, T.SecureAnchor);
let W3C ∈ C W3C = new Context();
Context + Traits 11
... in JavaScriptContext Traits
T.SecureAnchorT.SecureAnchor
href
parent
visible
manager
...
Untrusted
let Default ∈ C Default = new Context();
a = new HTML.Anchor();let ida ∈ L
constitution: L ⨉ C → T
constitution( ida, W3C ) = W3C.adapt(a, T.ValidAnchor);
let Untrusted ∈ C Untrusted = new Context();
T.ValidAnchorT.ValidAnchor
addAttribute
setAttribute
removeAttribute
parent
...

45. Run-Time Trait Recomposition 12
overloading of constitution: L ⨉ C → Tconstitution: L ⨉ 2C
→ 2T
constitution ( ida, { Default, Untrusted, W3C } )
= { HTML.Anchor, T.SecureAnchor, T.ValidAnchor }

46. Run-Time Trait Recomposition 12
overloading of constitution: L ⨉ C → Tconstitution: L ⨉ 2C
→ 2T
defined through composition policiescomposition: 2T
→ O
constitution ( ida, { Default, Untrusted, W3C } )
= { HTML.Anchor, T.SecureAnchor, T.ValidAnchor }

47. o
addAttribute
setAttribute
removeAttribute
href
parent
visible
type
target
HTML.Anchor
addAttribute
setAttribute
removeAttribute
href
parent
visible
type
target
T.ValidAnchorT.ValidAnchor
addAttribute
setAttribute
removeAttribute
parent
...
T.SecureAnchorT.SecureAnchor
href
parent
visible
manager
...
Run-Time Trait Recomposition 12
overloading of constitution: L ⨉ C → Tconstitution: L ⨉ 2C
→ 2T
defined through composition policiescomposition: 2T
→ O
constitution ( ida, { Default, Untrusted, W3C } )
= { HTML.Anchor, T.SecureAnchor, T.ValidAnchor }
composition ( { HTML.Anchor, T.SecureAnchor, T.ValidAnchor } ) =
▹ ▹
overriding operator

48. o
addAttribute
setAttribute
removeAttribute
href
parent
visible
type
target
HTML.Anchor
addAttribute
setAttribute
removeAttribute
href
parent
visible
type
target
T.ValidAnchorT.ValidAnchor
addAttribute
setAttribute
removeAttribute
parent
...
T.SecureAnchorT.SecureAnchor
href
parent
visible
manager
...
Run-Time Trait Recomposition 12
overloading of constitution: L ⨉ C → Tconstitution: L ⨉ 2C
→ 2T
defined through composition policiescomposition: 2T
→ O
constitution ( ida, { Default, Untrusted, W3C } )
= { HTML.Anchor, T.SecureAnchor, T.ValidAnchor }
composition ( { HTML.Anchor, T.SecureAnchor, T.ValidAnchor } ) =
▹ ▹
addAttribute
setAttribute
removeAttribute
href
parent
visible
type
target
href
parent
visible
addAttribute
setAttribute
removeAttribute
parent

49. o
addAttribute
setAttribute
removeAttribute
href
parent
visible
type
target
Run-Time Trait Recomposition 12
overloading of constitution: L ⨉ C → Tconstitution: L ⨉ 2C
→ 2T
defined through composition policiescomposition: 2T
→ O
constitution ( ida, { Default, Untrusted, W3C } )
= { HTML.Anchor, T.SecureAnchor, T.ValidAnchor }
composition ( { HTML.Anchor, T.SecureAnchor, T.ValidAnchor } ) =
addAttribute
setAttribute
removeAttribute
href
parent
visible
type
target
href
parent
visible
addAttribute
setAttribute
removeAttribute
parent

50. o
addAttribute
setAttribute
removeAttribute
href
parent
visible
type
target
Run-Time Trait Recomposition 12
overloading of constitution: L ⨉ C → Tconstitution: L ⨉ 2C
→ 2T
defined through composition policiescomposition: 2T
→ O
constitution ( ida, { Default, Untrusted, W3C } )
= { HTML.Anchor, T.SecureAnchor, T.ValidAnchor }
composition ( { HTML.Anchor, T.SecureAnchor, T.ValidAnchor } ) =
object = composition · constitution
addAttribute
setAttribute
removeAttribute
href
parent
visible
type
target
href
parent
visible
addAttribute
setAttribute
removeAttribute
parent

51. o
addAttribute
setAttribute
removeAttribute
href
parent
visible
type
target
Run-Time Trait Recomposition 12
overloading of constitution: L ⨉ C → Tconstitution: L ⨉ 2C
→ 2T
defined through composition policiescomposition: 2T
→ O
constitution ( ida, { Default, Untrusted, W3C } )
= { HTML.Anchor, T.SecureAnchor, T.ValidAnchor }
composition ( { HTML.Anchor, T.SecureAnchor, T.ValidAnchor } ) =
puts object composition in direct
relationship to the context of execution
object: L ⨉ 2C
→ O
object = composition · constitution
addAttribute
setAttribute
removeAttribute
href
parent
visible
type
target
href
parent
visible
addAttribute
setAttribute
removeAttribute
parent

52. o
addAttribute
setAttribute
removeAttribute
href
parent
visible
type
target
Run-Time Trait Recomposition 12
overloading of constitution: L ⨉ C → Tconstitution: L ⨉ 2C
→ 2T
defined through composition policiescomposition: 2T
→ O
constitution ( ida, { Default, Untrusted, W3C } )
= { HTML.Anchor, T.SecureAnchor, T.ValidAnchor }
composition ( { HTML.Anchor, T.SecureAnchor, T.ValidAnchor } ) =
o = TC1 · TC2 · ... · TCn
puts object composition in direct
relationship to the context of execution
object: L ⨉ 2C
→ O
object = composition · constitution
addAttribute
setAttribute
removeAttribute
href
parent
visible
type
target
href
parent
visible
addAttribute
setAttribute
removeAttribute
parent

53. TD
Context-Driven Trait Composition
T1
T2
T3
T4
T5
13

54. TD
Context-Driven Trait Composition
T1
T2
T3
T4
T5
13

55. TD
Context-Driven Trait Composition
T1
T2
T3
T4
T5
13

56. TD
Context-Driven Trait Composition
T1
T2
T3
T4
T5
13

57. TD
Context-Driven Trait Composition
T1
T2
T3
T4
T5
13

58. addAttribute
setAttribute
removeAttribute
href
parent
visible
type
target
href
parent
visible
addAttribute
setAttribute
removeAttribute
parent
o
addAttribute
setAttribute
removeAttribute
href
parent
visible
type
target
addAttribute
setAttribute
removeAttribute
href
parent
visible
type
target
href
parent
visible
addAttribute
setAttribute
removeAttribute
parent
=
Composition Policies 14
HTML.Anchor T.SecureAnchor T.ValidAnchor▹ ▹

59. addAttribute
setAttribute
removeAttribute
href
parent
visible
type
target
href
parent
visible
addAttribute
setAttribute
removeAttribute
parent
o
addAttribute
setAttribute
removeAttribute
href
parent
visible
type
target
addAttribute
setAttribute
removeAttribute
href
parent
visible
type
target
href
parent
visible
addAttribute
setAttribute
removeAttribute
parent
=
Composition Policies 14
HTML.Anchor T.SecureAnchor T.ValidAnchor▹ ▹
o
addAttribute
setAttribute
removeAttribute
href
parent
visible
type
target
addAttribute
setAttribute
removeAttribute
href
parent
visible
type
target
href
parentparent
addAttribute
setAttribute
removeAttribute
What if we want to
bypass security of
visible?

60. addAttribute
setAttribute
removeAttribute
href
parent
visible
type
target
href
parent
visible
addAttribute
setAttribute
removeAttribute
parent
o
addAttribute
setAttribute
removeAttribute
href
parent
visible
type
target
addAttribute
setAttribute
removeAttribute
href
parent
visible
type
target
href
parent
visible
addAttribute
setAttribute
removeAttribute
parent
=
Composition Policies 14
HTML.Anchor T.SecureAnchor T.ValidAnchor▹ ▹
o
addAttribute
setAttribute
removeAttribute
href
parent
visible
type
target
addAttribute
setAttribute
removeAttribute
href
parent
visible
type
target
href
parentparent
addAttribute
setAttribute
removeAttribute
What if we want to
bypass security of
visible?
✗ Impossible with strict overriding semantics
(e.g. inheritance, mixins, COP layers)

61. addAttribute
setAttribute
removeAttribute
href
parent
visible
type
target
href
parent
visible
addAttribute
setAttribute
removeAttribute
parent
o
addAttribute
setAttribute
removeAttribute
href
parent
visible
type
target
addAttribute
setAttribute
removeAttribute
href
parent
visible
type
target
href
parent
visible
addAttribute
setAttribute
removeAttribute
parent
=
Composition Policies 14
HTML.Anchor T.SecureAnchor T.ValidAnchor▹ ▹
o
addAttribute
setAttribute
removeAttribute
href
parent
visible
type
target
addAttribute
setAttribute
removeAttribute
href
parent
visible
type
target
href
parentparent
addAttribute
setAttribute
removeAttribute
What if we want to
bypass security of
visible?
✗ Impossible with strict overriding semantics
(e.g. inheritance, mixins, COP layers)
Povr ( { HTML.Anchor, T.SecureAnchor, T.ValidAnchor } ) =
{ }

62. Pbysec ( { HTML.Anchor, T.SecureAnchor, T.ValidAnchor } ) =
{ HTML.Anchor, T.SecureAnchor – visible, T.ValidAnchor }
addAttribute
setAttribute
removeAttribute
href
parent
visible
type
target
href
parent
visible
addAttribute
setAttribute
removeAttribute
parent
o
addAttribute
setAttribute
removeAttribute
href
parent
visible
type
target
addAttribute
setAttribute
removeAttribute
href
parent
visible
type
target
href
parent
visible
addAttribute
setAttribute
removeAttribute
parent
=
Composition Policies 14
HTML.Anchor T.SecureAnchor T.ValidAnchor▹ ▹
o
addAttribute
setAttribute
removeAttribute
href
parent
visible
type
target
addAttribute
setAttribute
removeAttribute
href
parent
visible
type
target
href
parentparent
addAttribute
setAttribute
removeAttribute
What if we want to
bypass security of
visible?
✗ Impossible with strict overriding semantics
(e.g. inheritance, mixins, COP layers)
Povr ( { HTML.Anchor, T.SecureAnchor, T.ValidAnchor } ) =
{ }

63. Pbysec ( { HTML.Anchor, T.SecureAnchor, T.ValidAnchor } ) =
{ HTML.Anchor, T.SecureAnchor – visible, T.ValidAnchor }
addAttribute
setAttribute
removeAttribute
href
parent
visible
type
target
href
parent
visible
addAttribute
setAttribute
removeAttribute
parent
o
addAttribute
setAttribute
removeAttribute
href
parent
visible
type
target
addAttribute
setAttribute
removeAttribute
href
parent
visible
type
target
href
parent
visible
addAttribute
setAttribute
removeAttribute
parent
=
Composition Policies 14
HTML.Anchor T.SecureAnchor T.ValidAnchor▹ ▹
o
addAttribute
setAttribute
removeAttribute
href
parent
visible
type
target
addAttribute
setAttribute
removeAttribute
href
parent
visible
type
target
href
parentparent
addAttribute
setAttribute
removeAttribute
What if we want to
bypass security of
visible?
✗ Impossible with strict overriding semantics
(e.g. inheritance, mixins, COP layers)
exclusion operator
Povr ( { HTML.Anchor, T.SecureAnchor, T.ValidAnchor } ) =
{ }

64. Pbysec ( { HTML.Anchor, T.SecureAnchor, T.ValidAnchor } ) =
{ HTML.Anchor, T.SecureAnchor – visible, T.ValidAnchor }
addAttribute
setAttribute
removeAttribute
href
parent
visible
type
target
href
parent
visible
addAttribute
setAttribute
removeAttribute
parent
o
addAttribute
setAttribute
removeAttribute
href
parent
visible
type
target
addAttribute
setAttribute
removeAttribute
href
parent
visible
type
target
href
parent
visible
addAttribute
setAttribute
removeAttribute
parent
=
Composition Policies 14
HTML.Anchor T.SecureAnchor T.ValidAnchor▹ ▹
o
addAttribute
setAttribute
removeAttribute
href
parent
visible
type
target
addAttribute
setAttribute
removeAttribute
href
parent
visible
type
target
href
parentparent
addAttribute
setAttribute
removeAttribute
What if we want to
bypass security of
visible?
✗ Impossible with strict overriding semantics
(e.g. inheritance, mixins, COP layers)
Povr ( { HTML.Anchor, T.SecureAnchor, T.ValidAnchor } ) =
{ }
P : 2T
→ 2T
P = Povr · Pbysec

65. Pbysec ( { HTML.Anchor, T.SecureAnchor, T.ValidAnchor } ) =
{ HTML.Anchor, T.SecureAnchor – visible, T.ValidAnchor }
addAttribute
setAttribute
removeAttribute
href
parent
visible
type
target
href
parent
visible
addAttribute
setAttribute
removeAttribute
parent
o
addAttribute
setAttribute
removeAttribute
href
parent
visible
type
target
addAttribute
setAttribute
removeAttribute
href
parent
visible
type
target
href
parent
visible
addAttribute
setAttribute
removeAttribute
parent
=
✓Arbitrary combinations
Composition Policies 14
HTML.Anchor T.SecureAnchor T.ValidAnchor▹ ▹
o
addAttribute
setAttribute
removeAttribute
href
parent
visible
type
target
addAttribute
setAttribute
removeAttribute
href
parent
visible
type
target
href
parentparent
addAttribute
setAttribute
removeAttribute
What if we want to
bypass security of
visible?
✗ Impossible with strict overriding semantics
(e.g. inheritance, mixins, COP layers)
Povr ( { HTML.Anchor, T.SecureAnchor, T.ValidAnchor } ) =
{ }
P : 2T
→ 2T
P = Povr · Pbysec

66. T.ValidAnchorT.ValidAnchor
addAttribute
setAttribute
removeAttribute
parent
...
Behaviour Extensibility Challenge 15
HTML.Anchor
...
setAttribute
...

67. T.ValidAnchorT.ValidAnchor
addAttribute
setAttribute
removeAttribute
parent
...
Behaviour Extensibility Challenge 15
HTML.Anchor
...
setAttribute
...

68. T.ValidAnchorT.ValidAnchor
addAttribute
setAttribute
removeAttribute
parent
...
how to invoke overridden behaviour?
Behaviour Extensibility Challenge 15
HTML.Anchor
...
setAttribute
...

69. T.ValidAnchorT.ValidAnchor
addAttribute
setAttribute
removeAttribute
parent
...
how to invoke overridden behaviour?
Behaviour Extensibility Challenge 15
HTML.Anchor
...
setAttribute
...
[ htmlSetAttribute ↦ setAttribute ] =
HTML.Anchor’
...
setAttribute
htmlSetAttribute
...

70. T.ValidAnchorT.ValidAnchor
addAttribute
setAttribute
removeAttribute
parent
...
how to invoke overridden behaviour?
Behaviour Extensibility Challenge 15
HTML.Anchor
...
setAttribute
...
[ htmlSetAttribute ↦ setAttribute ] =
HTML.Anchor’
...
setAttribute
htmlSetAttribute
...
aliasing operator

71. T.ValidAnchorT.ValidAnchor
addAttribute
setAttribute
removeAttribute
parent
...
how to invoke overridden behaviour?
Behaviour Extensibility Challenge 15
HTML.Anchor
...
setAttribute
...
[ htmlSetAttribute ↦ setAttribute ] =
HTML.Anchor’
...
setAttribute
htmlSetAttribute
...

72. T.ValidAnchorT.ValidAnchor
addAttribute
setAttribute
removeAttribute
parent
...
how to invoke overridden behaviour?
T.ValidAnchor.setAttribute = function(name, value) {
...
return self.htmlSetAttribute(name, value);
}
Behaviour Extensibility Challenge 15
T.ValidAnchor’T.ValidAnchor’
addAttribute
setAttribute
removeAttribute
parent
htmlSetAttribute
...
HTML.Anchor
...
setAttribute
...
[ htmlSetAttribute ↦ setAttribute ] =
HTML.Anchor’
...
setAttribute
htmlSetAttribute
...
→ manual edition →

73. T.ValidAnchorT.ValidAnchor
addAttribute
setAttribute
removeAttribute
parent
...
how to invoke overridden behaviour?
T.ValidAnchor.setAttribute = function(name, value) {
...
return self.htmlSetAttribute(name, value);
}
Behaviour Extensibility Challenge 15
T.ValidAnchor’T.ValidAnchor’
addAttribute
setAttribute
removeAttribute
parent
htmlSetAttribute
...
HTML.Anchor
...
setAttribute
...
[ htmlSetAttribute ↦ setAttribute ] =
HTML.Anchor’
...
setAttribute
htmlSetAttribute
...
→ manual edition →
...becomes requirement

74. T.ValidAnchorT.ValidAnchor
addAttribute
setAttribute
removeAttribute
parent
...
how to invoke overridden behaviour?
T.ValidAnchor.setAttribute = function(name, value) {
...
return self.htmlSetAttribute(name, value);
}
Behaviour Extensibility Challenge 15
T.ValidAnchor’T.ValidAnchor’
addAttribute
setAttribute
removeAttribute
parent
htmlSetAttribute
...
HTML.Anchor
...
setAttribute
...
[ htmlSetAttribute ↦ setAttribute ] =
HTML.Anchor’
...
setAttribute
htmlSetAttribute
...
→ manual edition →

75. T.ValidAnchorT.ValidAnchor
addAttribute
setAttribute
removeAttribute
parent
...
T.ValidAnchor.setAttribute = function(name, value) {
...
return self.htmlSetAttribute(name, value);
}
Behaviour Extensibility Challenge 15
T.ValidAnchor’T.ValidAnchor’
addAttribute
setAttribute
removeAttribute
parent
htmlSetAttribute
...
HTML.Anchor
...
setAttribute
...
[ htmlSetAttribute ↦ setAttribute ] =
HTML.Anchor’
...
setAttribute
htmlSetAttribute
...
→ manual edition →
▹

76. T.ValidAnchorT.ValidAnchor
addAttribute
setAttribute
removeAttribute
parent
...
T.ValidAnchor.setAttribute = function(name, value) {
...
return self.htmlSetAttribute(name, value);
}
Behaviour Extensibility Challenge 15
T.ValidAnchor’T.ValidAnchor’
addAttribute
setAttribute
removeAttribute
parent
htmlSetAttribute
...
HTML.Anchor
...
setAttribute
...
[ htmlSetAttribute ↦ setAttribute ] =
HTML.Anchor’
...
setAttribute
htmlSetAttribute
...
→ manual edition →
▹
✗ bypassed T.SecureAnchor
▹▹

77. T.ValidAnchorT.ValidAnchor
addAttribute
setAttribute
removeAttribute
parent
...
T.ValidAnchor.setAttribute = function(name, value) {
...
return self.htmlSetAttribute(name, value);
}
Behaviour Extensibility Challenge 15
T.ValidAnchor’T.ValidAnchor’
addAttribute
setAttribute
removeAttribute
parent
htmlSetAttribute
...
HTML.Anchor
...
setAttribute
...
[ htmlSetAttribute ↦ setAttribute ] =
HTML.Anchor’
...
setAttribute
htmlSetAttribute
...
→ manual edition →
▹
✗ bypassed T.SecureAnchor
▹▹
✗ hard-coded choice of
overridden behaviour

78. Extensibility Through proceed 16
HTML.Anchor
...
setAttribute
...
T.ValidAnchorT.ValidAnchor
addAttribute
setAttribute
removeAttribute
parent
how to invoke overridden behaviour?

79. T.ValidAnchor = Trait({
setAttribute: function(name, value) {
... // validity check
return self.proceed();
},
...
});
Extensibility Through proceed 16
HTML.Anchor
...
setAttribute
...
T.ValidAnchorT.ValidAnchor
addAttribute
setAttribute
removeAttribute
parent
how to invoke overridden behaviour?
proceed

80. T.ValidAnchor = Trait({
setAttribute: function(name, value) {
... // validity check
return self.proceed();
},
...
});
Extensibility Through proceed 16
HTML.Anchor
...
setAttribute
...
T.ValidAnchorT.ValidAnchor
addAttribute
setAttribute
removeAttribute
parent
becomes requirement
how to invoke overridden behaviour?
proceed

81. T.ValidAnchor = Trait({
setAttribute: function(name, value) {
... // validity check
return self.proceed();
},
...
});
Extensibility Through proceed 16
HTML.Anchor
...
setAttribute
...
T.ValidAnchorT.ValidAnchor
addAttribute
setAttribute
removeAttribute
parent
how to invoke overridden behaviour?
proceed

82. T.ValidAnchor = Trait({
setAttribute: function(name, value) {
... // validity check
return self.proceed();
},
...
});
Extensibility Through proceed 16
HTML.Anchor
...
setAttribute
...
T.ValidAnchorT.ValidAnchor
addAttribute
setAttribute
removeAttribute
parent
✓ open choice of
overridden behaviour
how to invoke overridden behaviour?
proceed

83. T.ValidAnchor = Trait({
setAttribute: function(name, value) {
... // validity check
return self.proceed();
},
...
});
Extensibility Through proceed 16
HTML.Anchor
...
setAttribute
...
T.ValidAnchorT.ValidAnchor
addAttribute
setAttribute
removeAttribute
parent
how to invoke overridden behaviour?
proceed
▹
T.SecureAnchorT.SecureAnchor
...
setAttribute
...
parent
visible
manager
...
▹

84. T.ValidAnchor = Trait({
setAttribute: function(name, value) {
... // validity check
return self.proceed();
},
...
});
Extensibility Through proceed 16
HTML.Anchor
...
setAttribute
...
T.ValidAnchorT.ValidAnchor
addAttribute
setAttribute
removeAttribute
parent
how to invoke overridden behaviour?
proceed
▹
T.SecureAnchorT.SecureAnchor
...
setAttribute
...
parent
visible
manager
...
▹

85. T.Extensible
proceed
Dynamic
T.ValidAnchor = Trait({
setAttribute: function(name, value) {
... // validity check
return self.proceed();
},
...
});
Extensibility Through proceed 16
HTML.Anchor
...
setAttribute
...
T.ValidAnchorT.ValidAnchor
addAttribute
setAttribute
removeAttribute
parent
how to invoke overridden behaviour?
proceed
▹
T.SecureAnchorT.SecureAnchor
...
setAttribute
...
parent
visible
manager
...
▹

86. ‣ Contexts: frame of reference to define adaptations
‣ Traits: convenient units of adaptation
‣ Policies: flexible compositions (e.g. non-linear)
‣ Extensibility: independent behaviour extensions
‣ JavaScript: easy definition of contexts, traits, and
composition
Summary 17

87. ‣ Contexts: frame of reference to define adaptations
‣ Traits: convenient units of adaptation
‣ Policies: flexible compositions (e.g. non-linear)
‣ Extensibility: independent behaviour extensions
‣ JavaScript: easy definition of contexts, traits, and
composition
Summary 17
direct causal connection
composition of the computational system
situation in which the system executes
⇋

88. In The Paper
‣ Default composition policy
‣ Resolution of proceed chains through policies
‣ Implementation technique for proceed
‣ Case Studies
18

89. Questions?
Context Traits
19

90. Additional Slides

91. Resolution of proceed Through Policies 21
a b
c d
T1
c g
q
T2c() { ... self.proceed() ... }
c d
e f
c h
T3
· · ·

92. Resolution of proceed Through Policies 21
a b
c d
T1
c g
q
T2c() { ... self.proceed() ... }
c d
e f
c h
T3
· · ·

93. Resolution of proceed Through Policies 21
pairwise resolution: Pg ( { T2, T3 } ) = { TR }
a b
c d
T1
c g
q
T2c() { ... self.proceed() ... }
c d
e f
c h
T3
· · ·

94. Resolution of proceed Through Policies 21
pairwise resolution: Pg ( { T2, T3 } ) = { TR }
a b
c d
T1
c g
q
T2
either TR ( c ) = or TR ( c ) =c c
( since policies resolve through +, ▹, ↦, – exclusively )
c() { ... self.proceed() ... }
c d
e f
c h
T3
· · ·

95. Resolution of proceed Through Policies 21
pairwise resolution: Pg ( { T2, T3 } ) = { TR }
a b
c d
T1
c g
q
T2
either TR ( c ) = or TR ( c ) =c c
( since policies resolve through +, ▹, ↦, – exclusively )
c() { ... self.proceed() ... }
c d
e f
suppose TR ( c ) = ; then <c cc
c h
T3
· · ·

96. Resolution of proceed Through Policies 22
Pg induces an order < < <c ccc
c() { ... self.proceed() ... }
current next

97. Resolution of proceed Through Policies 22
Pg induces an order < < <c ccc
c() { ... self.proceed() ... }
current next
c<

98. Resolution By Activation Age
Default policy Pa
23

99. Resolution By Activation Age
C1 < C2 < ... < Cnyounger older
Default policy Pa
23

100. Resolution By Activation Age
Pa ( { TC1, TC2, ... , TCn } ) = { TC1 ▹ TC2 ▹ ... ▹ TCn }
C1 < C2 < ... < Cnyounger older
Default policy Pa
23

101. Resolution By Activation Age
Pa ( { TC1, TC2, ... , TCn } ) = { TC1 ▹ TC2 ▹ ... ▹ TCn }
C1 < C2 < ... < Cnyounger older
produces a sort of
layering according to
contexts
a b
c dc d
e f
TC1
TC2
e f
g h
TC3
Default policy Pa
23

102. m n
c d
TD
Resolution By Activation Age
Pa ( { TC1, TC2, ... , TCn } ) = { TC1 ▹ TC2 ▹ ... ▹ TCn }
C1 < C2 < ... < Cnyounger older
produces a sort of
layering according to
contexts
a b
c dc d
e f
TC1
TC2
e f
g h
TC3
Default policy Pa
23

103. Licence 24
creativecommons.org/licenses/by-nc-sa/3.0