In Programing Pearls, the noted computer-science aphorist Jon Bentley comments on Brooks's observation with “If you plan to throw one away, you will throw away two.” He is almost certainly right. The point of Brooks's observation, and Bentley's, isn't merely that you should expect first attempt to be wrong, it's that starting over with the right idea is usually more effective than trying to salvage a mess.
Examples of successful open-source, bazaar development predating the Internet explosion and unrelated to the Unix and Internet traditions have existed. The development of the info-Zip (http://www.cdrom.com/pub/infozip/) compression utility during 1990-x1992, primarily for DOS machines, was one such example. Another was the RBBS bulletin board system (again for DOS), which began in 1983 and developed a sufficiently strong community that there have been fairly regular releases up to the present (mid-1999) despite the huge technical advantages of Internet mail and file-sharing over local BBSs. While the info-Zip community relied to some extent on Internet mail, the RBBS developer culture was actually able to base a substantial on-line community on RBBS that was completely independent of the TCP/IP infrastructure.
That transparency and peer review are valuable for taming the complexity of OS development turns out, after all, not to be a new concept. In 1965, very early in the history of time-sharing operating systems, Corbató and Vyssotsky, co-designers of the Multics operating system, http://www.multicians.org/fjcc1.html wrote:
It is expected that the Multics system will be published when it is operating substantially... Such publication is desirable for two reasons: First, the system should withstand public scrutiny and criticism volunteered by interested readers; second, in an age of increasing complexity, it is an obligation to present and future system designers to make the inner operating system as lucid as possible so as to reveal the basic system issues.
John Hasler has suggested an interesting explanation for the fact that duplication of effort doesn't seem to be a net drag on open-source development. He proposes what I'll dub “Hasler's Law”: the costs of duplicated work tend to scale sub-qadratically with team size—that is, more slowly than the planning and management overhead that would be needed to eliminate them.
This claim actually does not contradict Brooks's Law. It may be the case that total complexity overhead and vulnerability to bugs scales with the square of team size, but that the costs from duplicated work are nevertheless a special case that scales more slowly. It's not hard to develop plausible reasons for this, starting with the undoubted fact that it is much easier to agree on functional boundaries between different developers' code that will prevent duplication of effort than it is to prevent the kinds of unplanned bad interactions across the whole system that underly most bugs.
The combination of Linus's Law and Hasler's Law suggests that there are actually three critical size regimes in software projects. On small projects (I would say one to at most three developers) no management structure more elaborate than picking a lead programmer is needed. And there is some intermediate range above that in which the cost of traditional management is relatively low, so its benefits from avoiding duplication of effort, bug-tracking, and pushing to see that details are not overlooked actually net out positive.
Above that, however, the combination of Linus's Law and Hasler's Law suggests there is a large-project range in which the costs and problems of traditional management rise much faster than the expected cost from duplication of effort. Not the least of these costs is a structural inability to harness the many-eyeballs effect, which (as we've seen) seems to do a much better job than traditional management at making sure bugs and details are not overlooked. Thus, in the large-project case, the combination of these laws effectively drives the net payoff of traditional management to zero.
The split between Linux's experimental and stable versions has another function related to, but distinct from, hedging risk. The split attacks another problem: the deadliness of deadlines. When programmers are held both to an immutable feature list and a fixed drop-dead date, quality goes out the window and there is likely a colossal mess in the making. I am indebted to Marco Iansiti and Alan MacCormack of the Harvard Business School for showing me me evidence that relaxing either one of these constraints can make scheduling workable.
One way to do this is to fix the deadline but leave the feature list flexible, allowing features to drop off if not completed by deadline. This is essentially the strategy of the "stable" kernel branch; Alan Cox (the stable-kernel maintainer) puts out releases at fairly regular intervals, but makes no guarantees about when particular bugs will be fixed or what features will beback-ported from the experimental branch.
The other way to do this is to set a desired feature list and deliver only when it is done. This is essentially the strategy of the “experimental” kernel branch. De Marco and Lister cited research showing that this scheduling policy ("wake me up when it's done") produces not only the highest quality but, on average, shorter delivery times than either "realistic" or "aggressive" scheduling.
I have come to suspect (as of early 2000) that in earlier versions of this essay I severely underestimated the importance of the “wake me up when it's done” anti-deadline policy to the open-source community's productivity and quality. General experience with the rushed GNOME 1.0 release in 1999 suggests that pressure for a premature release can neutralize many of the quality benefits open source normally confers.
It may well turn out to be that the process transparency of open source is one of three co-equal drivers of its quality, along with “wake me up when it's done” scheduling and developer self-selection.
It's tempting, and not entirely inaccurate, to see the core-plus-halo organization characteristic of open-source projects as an Internet-enabled spin on Brooks's own recommendation for solving the N-squared complexity problem, the "surgical-team" organization—but the differences are significant. The constellation of specialist roles such as "code librarian" that Brooks envisioned around the team leader doesn't really exist; those roles are executed instead by generalists aided by toolsets quite a bit more powerful than those of Brooks's day. Also, the open-source culture leans heavily on strong Unix traditions of modularity, APIs, and information hiding—none of which were elements of Brooks's prescription.
The respondent who pointed out to me the effect of widely varying trace path lengths on the difficulty of characterizing a bug speculated that trace-path difficulty for multiple symptoms of the same bug varies "exponentially" (which I take to mean on a Gaussian or Poisson distribution, and agree seems very plausible). If it is experimentally possible to get a handle on the shape of this distribution, that would be extremely valuable data. Large departures from a flat equal-probability distribution of trace difficulty would suggest that even solo developers should emulate the bazaar strategy by bounding the time they spend on tracing a given symptom before they switch to another. Persistence may not always be a virtue...
An issue related to whether one can start projects from zero in the bazaar style is whether the bazaar style is capable of supporting truly innovative work. Some claim that, lacking strong leadership, the bazaar can only handle the cloning and improvement of ideas already present at the engineering state of the art, but is unable to push the state of the art. This argument was perhaps most infamously made by the Halloween Documents, http://www.opensource.org/halloween/, two embarrassing internal Microsoft memoranda written about the open-source phenomenon. The authors compared Linux's development of a Unix-like operating system to “chasing taillights”, and opined “(once a project has achieved "parity" with the state-of-the-art), the level of management necessary to push towards new frontiers becomes massive.”
There are serious errors of fact implied in this argument. One is exposed when the Halloween authors themseselves later observe that “often [...] new research ideas are first implemented and available on Linux before they are available / incorporated into other platforms.”
If we read “open source” for “Linux”, we see that this is far from a new phenomenon. Historically, the open-source community did not invent Emacs or the World Wide Web or the Internet itself by chasing taillights or being massively managed—and in the present, there is so much innovative work going on in open source that one is spoiled for choice. The GNOME project (to pick one of many) is pushing the state of the art in GUIs and object technology hard enough to have attracted considerable notice in the computer trade press well outside the Linux community. Other examples are legion, as a visit to Freshmeat, http://freshmeat.net/, on any given day will quickly prove.
But there is a more fundamental error in the implicit assumption that the cathedral model (or the bazaar model, or any other kind of management structure) can somehow make innovation happen reliably. This is nonsense. Gangs don't have breakthrough insights—even volunteer groups of bazaar anarchists are usually incapable of genuine originality, let alone corporate committees of people with a survival stake in some status quo ante. Insight comes from individuals. The most their surrounding social machinery can ever hope to do is to be responsive to breakthrough insights—to nourish and reward and rigorously test them instead of squashing them.
Some will characterize this as a romantic view, a reversion to outmoded lone-inventor stereotypes. Not so; I am not asserting that groups are incapable of developing breakthrough insights once they have been hatched; indeed, we learn from the peer-review process that such development groups are essential to producing a high-quality result. Rather I am pointing out that every such group development starts from—is necessarily sparked by—one good idea in one person's head. Cathedrals and bazaars and other social structures can catch that lightning and refine it, but they cannot make it on demand.
Therefore the root problem of innovation (in software, or anywhere else) is indeed how not to squash it—but, even more fundamentally, it is how to grow lots of people who can have insights in the first place.
To suppose that cathedral-style development could manage this trick but the low entry barriers and process fluidity of the bazaar cannot would be absurd. If what it takes is one person with one good idea, then a social milieu in which one person can rapidly attract the cooperation of hundreds or thousands of others with that good idea is going inevitably to out-innovate any in which the person has to do a political sales job to a hierarchy before he can work on his idea without risk of getting fired.
And, indeed, if we look at the history of software innovation by organizations using the cathedral model, we quickly find it is rather rare. Large corporations rely on university research for new ideas (thus the Halloween Documents authors' unease about Linux's facility at coopting that research more rapidly). Or they buy out small companies built around some innovator's brain. In neither case is the innovation native to the cathedral culture; indeed, many innovations so imported end up being quietly suffocated under the "massive level of management" the Halloween Documents' authors so extol.
That, however, is a negative point. The reader would be better served by a positive one. I suggest, as an experiment, the following:
Pick a criterion for originality that you believe you can apply consistently. If your definition is “I know it when I see it”, that's not a problem for purposes of this test.
Pick any closed-source operating system competing with Linux, and a best source for accounts of current development work on it.
Watch that source and Freshmeat for one month. Every day, count the number of release announcements on Freshmeat that you consider “original” work. Apply the same definition of “original” to announcements for that other OS and count them.
Thirty days later, total up both figures.
The day I wrote this, Freshmeat carried twenty-two release announcements, of which three appear they might push state of the art in some respect, This was a slow day for Freshmeat, but I will be astonished if any reader reports as many as three likely innovations a month in any closed-source channel.
We now have history on a project that, in several ways, may provide a more indicative test of the bazaar premise than fetchmail; EGCS, http://egcs.cygnus.com/, the Experimental GNU Compiler System.
This project was announced in mid-August of 1997 as a conscious attempt to apply the ideas in the early public versions of Chapter 2. The project founders felt that the development of GCC, the Gnu C Compiler, had been stagnating. For about twenty months afterwards, GCC and EGCS continued as parallel products—both drawing from the same Internet developer population, both starting from the same GCC source base, both using pretty much the same Unix toolsets and development environment. The projects differed only in that EGCS consciously tried to apply the bazaar tactics I have previously described, while GCC retained a more cathedral-like organization with a closed developer group and infrequent releases.
This was about as close to a controlled experiment as one could ask for, and the results were dramatic. Within months, the EGCS versions had pulled substantially ahead in features; better optimization, better support for FORTRAN and C++. Many people found the EGCS development snapshots to be more reliable than the most recent stable version of GCC, and major Linux distributions began to switch to EGCS.
In April of 1999, the Free Software Foundation (the official sponsors of GCC) dissolved the original GCC development group and officially handed control of the project to the the EGCS steering team.
Of course, Kropotkin's critique and Linus's Law raise some wider issues about the cybernetics of social organizations. Another folk theorem of software engineering suggests one of them; Conway's Law—commonly stated as “If you have four groups working on a compiler, you'll get a 4-pass compiler”. The original statement was more general: “Organizations which design systems are constrained to produce designs which are copies of the communication structures of these organizations.” We might put it more succinctly as “The means determine the ends”, or even “Process becomes product”.
It is accordingly worth noting that in the open-source community organizational form and function match on many levels. The network is everything and everywhere: not just the Internet, but the people doing the work form a distributed, loosely coupled, peer-to-peer network that provides multiple redundancy and degrades very gracefully. In both networks, each node is important only to the extent that other nodes want to cooperate with it.
The peer-to-peer part is essential to the community's astonishing productivity. The point Kropotkin was trying to make about power relationships is developed further by the “SNAFU Principle”: “True communication is possible only between equals, because inferiors are more consistently rewarded for telling their superiors pleasant lies than for telling the truth.” Creative teamwork utterly depends on true communication and is thus very seriously hindered by the presence of power relationships. The open-source community, effectively free of such power relationships, is teaching us by contrast how dreadfully much they cost in bugs, in lowered productivity, and in lost opportunities.
Further, the SNAFU principle predicts in authoritarian organizations a progressive disconnect between decision-makers and reality, as more and more of the input to those who decide tends to become pleasant lies. The way this plays out in conventional software development is easy to see; there are strong incentives for the inferiors to hide, ignore, and minimize problems. When this process becomes product, software is a disaster.
I quoted several bits from Frederick P. Brooks's classic The Mythical Man-Month because, in many respects, his insights have yet to be improved upon. I heartily recommend the 25th Anniversary edition from Addison-Wesley (ISBN 0-201-83595-9), which adds his 1986 “No Silver Bullet” paper.
The new edition is wrapped up by an invaluable 20-years-later retrospective in which Brooks forthrightly admits to the few judgements in the original text which have not stood the test of time. I first read the retrospective after the first public version of this essay was substantially complete, and was surprised to discover that Brooks attributed bazaar-like practices to Microsoft! (In fact, however, this attribution turned out to be mistaken. In 1998 we learned from the Halloween Documents (http://www.opensource.org/halloween/) that Microsoft's internal developer community is heavily balkanized, with the kind of general source access needed to support a bazaar not even truly possible.)
Gerald M. Weinberg's The Psychology Of Computer Programming (New York, Van Nostrand Reinhold 1971) introduced the rather unfortunately-labeled concept of “egoless programming”. While he was nowhere near the first person to realize the futility of the “principle of command”, he was probably the first to recognize and argue the point in particular connection with software development.
Richard P. Gabriel, contemplating the Unix culture of the pre-Linux era, reluctantly argued for the superiority of a primitive bazaar-like model in his 1989 paper “LISP: Good News, Bad News, and How To Win Big”. Though dated in some respects, this essay is still rightly celebrated among LISP fans (including me). A correspondent reminded me that the section titled “Worse Is Better” reads almost as an anticipation of Linux. The paper is accessible on the World Wide Web at http://www.naggum.no/worse-is-better.html">http://www.naggum.no/worse-is-better.html.
De Marco and Lister's Peopleware: Productive Projects and Teams (New York; Dorset House, 1987; ISBN 0-932633-05-6) is an underappreciated gem which I was delighted to see Fred Brooks cite in his retrospective. While little of what the authors have to say is directly applicable to the Linux or open-source communities, the authors' insight into the conditions necessary for creative work is acute and worthwhile for anyone attempting to import some of the bazaar model's virtues into a commercial context.
Finally, I must admit that I very nearly called this essay “The Cathedral and the Agora”, the latter term being the Greek for an open market or public meeting place. The seminal “agoric systems” papers by Mark Miller and Eric Drexler, by describing the emergent properties of market-like computational ecologies, helped prepare me to think clearly about analogous phenomena in the open-source culture when Linux rubbed my nose in them five years later. These papers are available on the Web at http://www.agorics.com/agorpapers.html.
This essay was improved by conversations with a large number of people who helped debug it. Particular thanks to Jeff Dutky email@example.com, who suggested the “debugging is parallelizable” formulation, and helped develop the analysis that proceeds from it. Also to Nancy Lebovitz firstname.lastname@example.org for her suggestion that I emulate Weinberg by quoting Kropotkin. Perceptive criticisms also came from Joan Eslinger email@example.com and Marty Franz firstname.lastname@example.org of the General Technics list. Glen Vandenburg email@example.com pointeed out the importance of self-selection in contributor populations and suggested the fruitful idea that much development rectifies “bugs of omission”; Daniel Upper firstname.lastname@example.org suggested the natural analogies for this. I'm grateful to the members of PLUG, the Philadelphia Linux User's group, for providing the first test audience for the first public version of this essay. Paula Matuszek email@example.com enlightened me about the practice of software management. Phil Hudson firstname.lastname@example.org reminded me that the social organization of the hacker culture mirrors the organization of its software, and vice-versa. John Buck email@example.com pointed out that MATLAB makes an instructive parallel to Emacs. Russell Johnston firstname.lastname@example.org brought me to consciousness about some of the mechanisms discussed in “How Many Eyeballs Tame Complexity.” Finally, Linus Torvalds's comments were helpful and his early endorsement very encouraging.