1. Product Line Engineering and Feature Models
CPSC 410

2. Reading for Monday REST Topics
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 ConstraintsX 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

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

22. 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.