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

The Cathedral and the Bazaar: A Look at Open-Source. ECE 417/617: Elements of Software Engineering. Stan Birchfield Clemson University. Cathedral Well-organized, full-time development team Followed by corporate teams. Bazaar Loosely-organized, volunteer “hackers”.

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

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  1. The Cathedral and the Bazaar: A Look at Open-Source ECE 417/617:Elements of Software Engineering Stan Birchfield Clemson University

  2. Cathedral Well-organized, full-time development team Followed by corporate teams Bazaar Loosely-organized, volunteer “hackers” Two ways to develop Software Can it work? [Eric Raymond, “The cathedral and the bazaar”, 1999]

  3. Fetchmail story • Need: access mail from stand-alone computer that’s not always on-line • Can’t 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 developer’s personal itch” • “Necessity is the mother of invention”

  5. Don’t 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-implement 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 • “I’m 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 they’re 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 won’t usually need your [code]; it’ll 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 they’re 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 you’re right

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