1. Maintainability of FLOSS Projects
Researching the evolution of GNU Emacs text editor
Ari Roponen

2. Contents About Myself Maintainability Software Evolution
FLOSS (Free/Libre/Open Source Software)
GNU Emacs
Aim of My Research
Current Status

3. About Myself Ari Roponen B.Eng. 2003, Jyväskylä Polytechnic
Bachelor’s thesis: ”Design and Implementation of a Route-Information System”
M.Sc. 2007, University of Jyväskylä
Master’s thesis: ”Open Source Version Control Systems”
GNU Emacs user since 2001

4. Maintainability
Maintenance means modifying software after it is published
Fix bugs
Improve performance
Adapt to environment changes
Maintainability = how well software can be maintained
Understandability
Modularity …

5. Software Evolution Software Evolution Laws (M. Lehman)
Continuing Change
Increasing Complexity
Self Regulation
Conservation of Organizational Stability
Conservation of Familiarity
Continuous Growth
Declining Quality
Feedback System
Conclusion: Continuous maintenance is needed to keep software functional in the changing environment

6. FLOSS (Free/Libre/Open Source Software)
Free Software
Richard Stallman
”Free as in freedom”
GNU, GPL, GCC, Emacs, ...
Open Source Software
Eric S. Raymond, Linus Torvalds
”OSS is a marketing name for FS”
Linux-kernel, Firefox
Is it important to separate FS from OSS?
Free/Libre/Open Source Software

7. GNU Emacs
“Emacs is the extensible, customizable, self-documenting real-time display editor.”
Richard Stallman wrote the first EMACS in 1976
GNU Emacs in 1984

9. Wow! How do you do that?
”First, write a Tetris-clone, then a shell, then a web browser, then ...”
Start the project, let others use it, integrate their changes, repeat at step 2, ...
There must be some kind of a development process...
... a good one

10. Aim of My Research (1/4)
Find out how FLOSS projects can get so old and still be up-to-date
Does FLOSS development differ from other software development?
GNU Emacs is 25 years old
Linux-kernel is 19 years old

11. Aim of My Research (2/4)
Detect common properties of FLOSS projects’ development models
Goal definition
Code writing
Documentation
Testing
Maintenance
Release cycle

12. Aim of My Research (3/4)
Maybe invent a model for characterising used development processes
Software changes by patching
Testing by developers/users/pretesters
Releasing early/late/”never”
Attracting new users/developers

13. Aim of My Research (4/4) Find new software evolution laws
Linux-kernel seems to grow faster than expected – why?
Do Lehman’s laws apply to FLOSS projects?

14. Current Status (1/4) How to keep software lifetime long
Personal characteristics
Be interested in what you do
Make your work useful for others
Be friendly to new users
Don’t neglect old users
Process characteristics
Use suitable (public) development model
Aim for good, not best
Design with extensibility in mind

15. Current Status (2/4) Common properties of old FLOSS projects
Changes reviewed by community
Existing coding standards
Many old users (including original authors)
Good documentation
No specific goals

16. Current Status (3/4) A model for FLOSS development
Software changes by patching
What is a patch
How changes get accepted
Properties of a good patch

17. Current Status (4/4) New evolution laws None (yet)
Existing laws seem to apply quite well

18. Questions?

19. Answers
GNU Emacs is available at
Yes No 42
Well, let me put it this way...
Thank You!