The Cathedral and the Bazaar: A Look at Open-Source

1
The Cathedral and the Bazaar A Look at
Open-Source
ECE 417/617Elements of Software Engineering
Stan Birchfield Clemson University
2
Two ways to develop Software

• Cathedral
• Well-organized, full-time development team
• Followed by corporate teams

• Bazaar
• Loosely-organized, volunteer hackers

Can it work?
Eric Raymond, The cathedral and the bazaar,
1999
3
Fetchmail story

• Need access mail from stand-alone computer
  thats not always on-line
• Cant simply forward
• POP3 server available, need POP3 client
• Obvious feature missing from existing clients
  replying to email from stand-alone computer (need
  to tack on end of email address)

4
Initial motivation

• Every good work of software starts by scratching
  a developers personal itch
• Necessity is the mother of invention

5
Dont reinvent the wheel

• Good programmers know what to write. Great ones
  know what to rewrite (and reuse).
• 9 existing programs were close
• Selected fetchpop first
• Linus Torvalds started, not from scratch, but
  with Minix

6
Never fear refactoring

• Plan to throw one away you will, anyhow.
  Brooks
• popclient by Carl Harris was more cleanly
  written, but lacked some key, difficult-to-impleme
  nt features
• Stay or switch?

7
Be kind and share

• When you lose interest in a program, your last
  duty is to hand it off to a competent successor.
• Carl Harris handed popclient code to Eric
  Raymond

8
Users as developers

• Treating your users as co-developers is your
  least-hassle route to rapid code improvement and
  effective debugging
• Power was underestimated until Linux
• Im basically a very lazy person who likes to
  get credit for things other people actually do
  Linus Torvalds

9
Release early, release often

• Cathedral
• Release often ? buggy code ? alienate users
• Bazaar
• Release often ? motivate developers ? maximize
  development time

10
Linus Law

• Linus Law Given enough eyeballs, all bugs are
  shallow.
• Given a large enough beta-tester and
  co-developer base, almost every problem will be
  characterized quickly and the fix obvious to
  someone.
• Debugging is parallelizable.
• Cathedral bugs are tricky, insidious, deep
  takes months of scrutiny by dedicated few to
  develop confidence that theyre all found
  inevitable disappointment when bugs appear in
  final release
• Bazaar bugs appear quickly with thousands of
  co-developers less to lose when bugs appear
• Delphi effect averaged opinion of a mass of
  observers (equally expert or ignorant) is more
  reliable than opinion of random observer
  sociologists
• Release early and often minimizes theoretical
  loss of efficiency due to duplication of effort
  by debuggers

11
Importance of data structures

• Which is more important, clean code or clean data
  structures?
• Smart data structures and dumb code works a lot
  better than the other way around.
• Show me your code and conceal your data
  structures, and I shall continue to be
  mystified. Show me your data structures, and I
  wont usually need your code itll be
  obvious. Brooks

12
Imitating Linux

• How did Raymonds imitate Linux?
• Releasing early and often
• Grew beta list by adding everyone who contacted
  him
• Emailed beta list, encouraging people to
  participate
• Listened to beta testers, polling them about
  design decisions and encouraging them when they
  sent patches and feedback
• Received bug reports, fixes, thoughtful
  criticism, feature suggestions, ...
• If you treat your beta-testers as if theyre
  your most valuable resource, they will respond by
  becoming your most valuable resource.

13
Strive for simplicity

• fetchmail was more complicated than it needed
  to be
• Late in the project, Raymond threw away a bulk of
  the code
• Result? Simpler manual, simpler setup, simpler
  configuration
• No lost functionality
• Perfection (in design) is achieved not when
  there is nothing more to add, but rather when
  there is nothing more to take away. Antoine de
  Saint-Exupery
• When code is getting better and simpler, you know
  youre right