Product Line Engineering and Feature Models

1. Product Line Engineering andFeature Models CPSC 410

2. Reading for Monday • REST Topics • http://www.infoq.com/articles/rest-introduction • Arch book p. 414–422 • Roy Fielding’s thesis perhaps most cited CS thesis, worth a scan if you want to see what one looks like.

3. Product Lines • Want to make several related products • Products share many common features • But features vary between products • Want a formal description of all possible product instances in a product line • Use Feature Models! • Model formalizes feature requirements • Does not address implementation

4. Software Product Line Example • Windows 7 Product Line • Starter • Home Premium • Professional • Ultimate

5. Informal Feature Matrix

6. Formal Feature Models

7. Cross-Tree Constraints X X X X Conflict Requires

8. Realistic Feature Model • For illustration purposes only • Uses extra syntax we don’t learn in this course

9. Mandatory Feature Product Line also referred to as Product Concept (denoted as C)

10. Optional Feature

11. eXclusive-Or (Alternative)

12. Inclusive-Or (Or)

13. Conflicting Features • Two features that cannot • exist in the same product • Used when features are not • siblings • {C}, {C, f1}, {C, f1, f2} • {C, f2}, {C, f1, f3} X X

14. Dependent Features • When one feature requires • another • Used when features are • not parent/child • {C}, {C, f1}, {C, f1, f2} • {C, f2}, {C, f1, f2, f3}

15. Feature Implementation • Often, a feature is not a class • Hence, feature models are not class diagrams • A feature can be implemented many ways • Class • Set of classes • A scattered set of methods • A scattered set of statements • etc… • The Feature Modeler does not concern themselves with such details

16. Example: Logging Feature class Account { private double total; public void deposit(double amount) { System.out.println(“User is depositing: “ + amount); … } public void withdraw(double amount) { System.out.println(“User is withdrawing: “ + amount); … } public double balance() { System.out.println(“User is checking balance”); … } } Where is the logging feature?

17. Example: Logging Feature class Account { private double total; public void deposit(double amount) { System.out.println (“User is depositing: “ + amount); … } public void withdraw(double amount) { System.out.println(“User is withdrawing: “ + amount); … } public double balance() { System.out.println(“User is checking balance”); … } } Where is the logging feature?

18. Where is Logging in Apache Tomcat? Picture from: Waterhouse and Kersten, kerstens.org/mik/publications/aspectj-tutorial-oopsla2004.ppt

19. Consider Your Project • At the end of the term … If I asked you where each User Story was in your code … • Most likely each User Story could not be isolated to a single • Class • Method • Statement • A good bonus mark candidate would be to describe your product using a feature model as described here.

20. Variability Implementation • How do we create variation in product lines? • Subclassing • Conditionals and IFDEF statements • Decorators/Connectors • Separate code bases • Likely to be different branches of a repository

21. Linux variability Linux has ~ 5400 features