1. Why Open Source Works Jim Herbsleb School of Computer Science
Carnegie Mellon University

2. Key Differences Open source Commercial Development work done by users
User-developers determine functionality
Developers choose work assignments
Emergent coordination spacer
Potentially redundant effort
Open technical discussions
Commercial
Developers seldom users
Product managers determine functionality
Management assigns work
Bureaucratic coordination
Redundant effort avoided
Closed technical discussions

3. Development Work Done by Users
Much more likely to get the functionality right
Major class of errors is eliminated
Unspoken, implicit, hidden requirements are not a problem
Extreme form of “participatory design”
Prototyping happens naturally

4. User-Developers Determine Functionality
Marketing and product management functions in commercial software
Very familiar with how purchasing decisions made
Often know very little about actual use, users
Often a huge gap between attributes that drive purchases and attributes that drive usefulness and usability
Decisions in open source based on user concerns, not purchaser concerns
Caveat -- non-developer users don’t count!

5. Developers Choose Work Assignments
Presumably many factors involved:
What is interesting and challenging
What functionality does that user/developer need
What is most likely to be included in the product
What will enhance reputation and standing
Developer choices range across projects
Larger pools of potential work assignments and developers permits better match
Requires efficient brokering

6. Emergent Coordination
Minimal management structure
Core group with commit privileges
Management by those with demonstrated technical merit
Participation mirrors dependencies
Very few developing new functionality
Many more fixing bugs
Very large numbers reporting bugs

7. Potentially Redundant Effort
Generates alternative solutions
Alternatives generated exactly where people are able to identify interesting technical alternatives
Sample many places on the risk/reward continuum
Alternatives have high option value

8. Open Technical Discussions
Draws on very large pool of potential experts
Newbies can catch up with minimal distractions to existing staff
Preserves design rationale

9. Productivity Core Developers Only5 10 15 20 25 30 35 40 45
MRs (X10)
KLOCA
Apache A B C D E
layout js
rdf
netwerk
editor
intl
xpinstall
Commercial
Mozilla
Mockus, A., Fielding, R., & Herbsleb, J.D.  Two Case Studies of Open Source Software Development: Apache and Mozilla (2002).  ACM Transactions on Software Engineering and Methodology, 11, 3, pp

10. “Post Feature Test” Defect Density

11. “Post Release” Defect Density14 28 10
0.1
0.7

12. Open Source Open Questions
Resource allocation process
Modeling, understanding
Brokerage tools
Effects of patronage, hybrid models
Security
Race from discovery to exploit to deployment
Race from discovery to patch to distribution and installation
Limitations of open source
Only maintenance and evolution?
How about highly collaborative stages like high-level design, architecture?
Collaboration technology