Kiczales and Mezini - FOAL 2005 1

AOP and Modular Reasoning [ICSE05]• Start with first-principles definition of modularity

and modular reasoning– localization, interfaces, enforcement, composition

• Provide example and analysis showing that:– in the presence of ccc, OOP is not modular– in the presence of ccc, AOP is modular

• But…– interfaces depend on system configuration– AOP makes that explicit– explains more about what crosscutting means

______[ICSE05] Kiczales and Mezini.

Kiczales and Mezini - FOAL 2005 2

• Aspect cuts interface– through Point and Line

• What crosscutting means

• The gestalt of AOP

aspect UpdateSignaling {

private Display Shape.display;

public void Shape.setDisplay(Display d) { this.display = d; }

pointcut change(Shape shape): this(shape) && (execution(void Shape.moveBy(int, int) || execution(void Shape+.set*(*)));

after(Shape s) returning: change(s) { Display.update(s); }}

Crosscutting Structure and Interfaces

class Line { private Point p1, p2;

Point getP1() { return p1; } Point getP2() { return p2; }

void setP1(Point p1) { this.p1 = p1; } void setP2(Point p2) { this.p2 = p2; }}

class Point {

private int x = 0, y = 0;

int getX() { return x; } int getY() { return y; }

void setX(int x) { this.x = x; } void setY(int y) { this.y = y; }}

Kiczales and Mezini - FOAL 2005 3

Parts

Kiczales and Mezini - FOAL 2005 4

Composed parts

• composition determines– both interfaces and component structure

m

Kiczales and Mezini - FOAL 2005 5

• Parts stay the same• Interfaces are extended• Declarative• What “details” means can change

aspect UpdateSignaling {

private Display Shape.display;

public void Shape.setDisplay(Display d) { this.display = d; }

pointcut change(Shape shape): this(shape) && (execution(void Shape.moveBy(int, int) || execution(void Shape+.set*(*)));

after(Shape s) returning: change(s) { Display.update(s); }}

Crosscutting Structure and Interfaces

class Line { private Point p1, p2;

Point getP1() { return p1; } Point getP2() { return p2; }

void setP1(Point p1) { this.p1 = p1; } void setP2(Point p2) { this.p2 = p2; }}

class Point {

private int x = 0, y = 0;

int getX() { return x; } int getY() { return y; }

void setX(int x) { this.x = x; } void setY(int y) { this.y = y; }}

Kiczales and Mezini - FOAL 2005 6

Why paper matters to us• What theory of AOP should say

– interface depends on configuration– “aspect control” systems can account for that– expand “modular” to encompass AOP

• that has been the idea for 10 years

• Stop focusing on advice and simple pointcuts!– inter-type declarations– more interesting pointcuts (i.e. dflow, pcflow…)– the fun is in saying

“there is a well-definable crosscutting interface there,I’m going to define it and program against it”

– a chance to play with all that fancy semantics (AOP as a strategic technology)