jgs SER 516 Software Agility Lecture 21: Dependency Principles III Dr. Javier Gonzalez-Sanchez [email protected] javiergs.engineering.asu.edu | javiergs.com PERALTA 230U Office Hours: By appointment

jgs Previously… Structural Quality

jgs 516 00010000 • Instability = Cout (Cin + Cout) Stable Abstraction Principle IC = 1.0, A= ? IX= 0.5, A= ? IA = 0.0, A= ?

jgs 516 00010000 Stable Abstraction Principle More stable a package is, the more abstract it should be.

jgs 516 00010000 Stable Abstraction Principle Abstract concrete Stable Hard to Change Only incoming dependencies Unstable Changeable Only outgoing dependencies

jgs 516 00010000 Question

jgs 516 00010000 Question A) B)

jgs Stable Dependency Principle

jgs 516 00010000 Stable Dependency Principle § Every dependency between modules should terminate on a module whose Instability metric is less than or equal to the depending module's Instability metric. § Every dependency between modules should terminate on a module whose Abstractness metric is greater than or equal to the depending module's Abstractness metric.

jgs 516 00010000 Question 3 (again) A) B)

jgs 516 00010000 SAP + SDP § Distance: how far a package is away from the Main Sequence § D = A + I – 1 § Values -1 to 1 § Absolute Distance |D|

jgs 516 00010000 Question project3.common.model project3.client.UI project3.server.controller

jgs 516 00010000 Question

jgs 516 00010000 Question public class Foo { Bar b= new Bar(new Car()); public Foo (Car c) { c.doIt(b); } public void m (Delta d) { d.action(b); } } public class System { public ... main ( ...) { Foo f = new Foo(); //... } }

jgs 516 00010000 Question public class Foo { Bar b= new Bar(new Car()); public Foo (Car c) { c.doIt(b); } public void m (Delta d) { d.action(b); } } public class System { public ... main ( ...) { Foo f = new Foo(); //... } } • Tangled: • ISystem = • IFoo = • IBar • Afoo • Any candidate for “painful” zone:

jgs 516 00010000 Question A:0 Ca:1 Ce:4 I:4/5=0.8 D:-0.2 A:0 Ca:2 Ce:3 I:3/5=0.6 D:-0.4 A:0 Ca:1 Ce:3 I:3/4=0.75 D:-0.25

jgs 516 00010000 Example

jgs 516 00010000 Reference § Agile Software Development: Principles, Patterns, and Practices. Robert C. Martin. Prentice Hall. 2006. Chapter 30.

jgs SER 516 Software Agility Javier Gonzalez-Sanchez [email protected] Spring 2021 Disclaimer. These slides can only be used as study material for the class SER516 at ASU. They cannot be distributed or used for another purpose.