jgs SER 516 Software Agility Lecture 19: Dependency Principles Dr. Javier Gonzalez-Sanchez [email protected] javiergs.engineering.asu.edu | javiergs.com PERALTA 230U Office Hours: By appointment 

jgs 516 00010000 Assignment 05 § Third Sprint Sprint Backlog Burndown Chart Retrospective Review Product – Source Code – Clean Source Code Product – Class Diagram– Clean Design Due date Assignment 5.3 – March 30 

jgs Previously 

jgs 516 00010000 Clean? 

jgs 516 00010000 Class Diagram? 

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jgs 516 00010000 Team 7 

jgs 516 00010000 Team 7 

jgs 516 00010000 Team 7 

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jgs Dependency Metrics Structural Quality 

jgs 516 00010000 Question 1 A) B) 

jgs 516 00010000 Question 2 Problem? Solution? 

jgs 516 00010000 Question 3 A) B) 

jgs 516 00010000 What could be measured or analyzed? A bad design smells. Robert C. Martin describes the following odors (among others): 1. Rigidity – The system is hard to change because every change forces many other changes. 2. Fragility – Changes cause the system to break in conceptually unrelated places. 3. Immobility – It’s hard to disentangle the system into reusable components. 4. Viscosity – Doing things right is harder than doing things wrong. 5. Opacity – It is hard to read and understand. It does not express its intent well. 

jgs 516 00010000 Goal § Measuring Quality § Dependency Analysis § Detect “potential” design flaws 

jgs 516 00010000 Principles 1. Acyclic Dependency Principle (ADP) 2. Stable Dependency Principle (SDP) 3. Stable Abstraction Principle (SAP) 

jgs Acyclic Dependency Principle 

jgs 516 00010000 Problem Definition § Cycled components can only be used together: they can only be tested, reused, deployed and understood together. § Every node on a cycle depends on any other. 

jgs 516 00010000 Acyclic Dependencies Principle § Avoid dependency cycles § Tangle. A subgraph with at least two nodes, where each node is reachable from each other. § Tangled metric. values greater zero indicate cyclic dependencies. 

jgs Stable Abstraction Principle 

jgs 516 00010000 Abstractness of a Package § Express the portion of contained abstract types. § It is a value 0 to 1: 0 (only concrete classes) to 1 (only interfaces and abstract classes) 

jgs 516 00010000 Instability of a Package § Indicates whether the package is mainly used by other artifacts (stable – hard to change) or if it mainly depends on other artifacts (instable – changeable). § It is a value 0 to 1: 0 only incoming dependencies to 1 (only outgoing dependencies) 

jgs 516 00010000 Instability of a Package § Indicates whether the package is mainly used by other artifacts (stable – hard to change) or if it mainly depends on other artifacts (instable – changeable). § It is a value 0 to 1: 0 only incoming dependencies to 1 (only outgoing dependencies) 

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

jgs To be continued… 

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.