Product Line Engineering and Feature Models CPSC 410

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.

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

Software Product Line Example Windows 7 Product Line Starter Home Premium Professional Ultimate

Informal Feature Matrix

Formal Feature Models

Cross-Tree Constraints X X X Conflict Requires

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

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

Optional Feature

eXclusive-Or (Alternative)

Inclusive-Or (Or)

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

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}

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

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?

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?

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

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.

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

Linux variability Linux has ~ 5400 features

Exercise Make a Feature Model for your favorite Automobile Product Line Use the “Build a Car” Wizard on their website to reverse-engineer the Feature Model You can use Chevrolet Don’t worry about being complete BUT … Try to find one example of each model element: Mandatory, Optional, Alternative, Or, Conflict, Requires Use paper/pencil(pen) and submit on Wed.