November 18, 2008

Thoughts on Stack Overflow

This is a short article detailing my thoughts on the recently released programming Q&A site, Stack Overflow.


Historically, I've had three resources for programming questions:

Over the course of 80 days, I've found Stack Overflow to be a better resource than all three of the above, even when combined.

The way I see it, Stack Overflow (hereby referred to as SO) is going strong for two fundamental reasons:

  1. SO baited the right community with the appropriate timing

  2. SO uses tags


If you think about it, there's nothing about SO that ties it to programming questions, aside from the constitution. (On SO, the constitution is the site FAQ). All in all, SO is a Q&A framework. If it's just a Q&A framework, how did SO manage to stay on topic and under control from its inception? They took the right members in with the right timing.

The beta test population was roughly given by the following:

Podcast listeners

(Jeff's readers UNION Joel's readers) - the relatively uninterested - attrition

Beta testers

(Podcast listeners INTERSECT people that cared enough about the programming Q&A site to find an obscure signup form) - more attrition

Joel Spolsky and Jeff Atwood are both well-known in the blogosphere among readers interested in improving their programming skills and doing software the Right Way. Beginning with their reader base (already amenable to their cause) there were two significant levels of filtration, as reflected in the above pseudo-formulae, that ensured that SO started off with a group of people who a) cared and b) had a significant body of knowledge with respect to programming and good software practices. This is just the kind of constituency that you want to impart some positive momentum on a fledgling Q&A site.

The private beta provided an adequate growth period so that, at release, there were enough core members with a solid conception of the constitution that they helped to create. Additionally, the core was able to uphold the tenets of the constitution with power from the reputation that they built. (If there were a third reason for the site's success, it would be how empowered the high-rep members are to uphold the constitution.)

If SO had been released to the public in a Hollywood Launch, without the beta momentum they had, I believe it would have failed. The framework is not programming-specific — the community is.


The site happens to be particularly well designed for programming questions in its tag-centric model. SO is a big pipe for programming questions with an unlimited number of virtual channels, each of which is denoted by a tag. With recently added capabilities to ignore or flag particular virtual channels, you (subtractively) take only the content that you want from the big pipe and prioritize the results. Exactly how nice this capability is will come to light when comparing SO to the other programming question outlets.

The tag model is also particularly well suited to the structure of knowledge in the programming domain, where the interests of individual constituents have a strong tendency to straddle several subdomains. Anecdotally, this is especially true for those who really care about their craft: the best programmers tend to have a great deal of depth to their knowledge, which inevitably ends up overlapping with other areas of interest. For example, most of today's great programmers use version control systems, convey information effectively through documentation, and recognize/employ design patterns. Many great programmers also understand than one programming paradigm and program in more than one language. When you mix a number of these programmers together, you get some really strong sauce. The tag system allows these members to cut out the noise and exchange information in their subdomains of expertise.

Community again: noobs

Don't take my subliminal messaging the wrong way: the noobs help. As they say, everybody starts out as a noob. It's clear that noobs pave the way for many others to follow by asking their noobish questions — that's rarely disputed. The really interesting thing is that noobs can provide a more brute force approach to answering questions correctly.

So long as the noobs are semi-informed, they're probably on SO because they're trying to learn about a topic of interest. Active learning processes are accompanied by reading and revisiting things that the more seasoned veterans haven't cared to think about in a long time. Noobs, with references fresh in their mind, can offer up suggestions or quotations (which they may or may not fully understand) while the rest of the members determine whether or not their information is helpful via votes and comments. Even if the noob's proposed answer is somehow incorrect, other members will learn exactly why. If other members thought the noob's answer was feasible as well, they'll be informed and corrected by seeing the dialog. This isn't something you get on an experts-only-answer site: interpolation of the truth through the correction of proposed answers.

There is, of course, the potential for Noobs of Mass Destruction (NMDs?) a la the Eternal September. If noobs outweigh the properly knowledgeable constituency so heavily that misconceptions are voted up far more rapidly than proper solutions, the site will suffer from a misinformation-shock. This misinformation may be corrected over time, but aside from Accepted Answers it's difficult to jump a correct answer to the top over highly up-voted incorrect answers. You need a critical mass of users that know what they're talking about to tip the scales with their votes and their arguments.

Lucky for us members, this didn't happen at public release. Even more lucky for the world of programmers, the success of the site and lack of an Eternal September-like phenomenon on SO will lead to more informed programmers from here forward, further reducing the chance for SO's quality to deteriorate. Really, it was just the initial gamble of going public and, as I mentioned before, SO got the timing right.

Community scaling through tagging

One of my favorite parts of all this is that tags allow the community scale beautifully. If SO gains a thousand new C# programmers as members, does that hurt, say, the Python programmers? No: because of tags, more members can only mean a better site. "Stack Overflow is biased towards C#" is not a self fulfilling prophesy. I'll explain why:

For argument's sake, let's say these are C# robots who only understand ways to use C# syntax to do what you want (i.e. "You can use regions to ease generated code injection. Beep."). If I'm a Python programmer who doesn't care about C#, I'm ignoring the tag anyway and don't get inundated with noise from the robots.

Inevitably, our hypothetical is incorrect and the C# programmers will all have knowledge which crosses into other subdomains. In the (slightly more realistic) case that the members are human beings who know C# along with some generic principles of programming and software design, they can only assist me in my cross-domain problems.

More C# programmers can only help the Python programmers. For all X and Y, more people interested in X can only help people interested in Y, so long as everybody tags everything appropriately. Except Lisp.

Comparison to other outlets

How does SO stack up against the alternatives? The primary differentiation comes in a few identifiable areas:


Folks on IRC, Usenet, or your buddy list have no real incentive to help you beyond the goodness of their hearts. I'm a starry-eyed idealist and I'm happy that this has worked historically, but it's readily apparent that people love playing for points. SO is one of those purely healthy forms of competition where everybody seems to win; from what I've seen, RTFM and "Google is Your Friend" trolls are consistently down-voted! The reputation system also appears to increase the responsiveness of the site — everybody is looking for the quick "Accepted Answer" grab if they can get it. I had figured that people would try to game the system, but it seems like most people with reputation have been sane, and the people with little reputation have their teeth pulled appropriately. Kudos to the karma system.

What differentiates SO from a big bulletin board is the three-tier threads. You have question (Original Poster), answer (many answers to one question), and comments (many comments to one answer). @replies allow for infinite "virtual" threading, but there's a clear indication of how the conversation is supposed to take place through the structure of the site. My experience with this format has led me to believe that it's ideal for removing noise from the answer tier (via short comments), without letting the meta-conversation get too crazy.

Threading on Usenet allows you to explore related topics of conversation with less friction, but it can be a big problem when you just want to know the answer that the Original Poster (OP) finally accepted. You often see such sub-conversations on Usenet get turned into new threads, while SO asks that you form the new thread pre-emptively as a new question. I have no problem with SO's approach, given the benefits of the three tiered conversation and the more precise indexing capabilities that result from structured threads.

Visibility of questions and answers is a big problem on IRC: there's a distinct fire-and-be-forgotten phenomenon in most channels, proportional to their noise level. Additionally, there's usually a few super gurus in each channel that can only handle one or two problems at a time, leading to,

[impatient-43/4] Can anybody answer my question^^!?!?

messages ad nauseum.


Usenet does better than IRC in terms of question visibility because it's an asynchronous medium. IRC's synchronous format makes help a lot more interactive, but at great cost. In addition to the fire-and-be-forgotten phenomenon, you inevitably juggle O(n) synchronous channels simultaneously, where n is the number of topics you're interested in.

Also, remember that chat is exactly that: you're going to get unwanted noise. Other people's Q&As, off topic conversation, and sometimes spammers all interfere with your ability to communicate a problem and get an answer in real time. If you've ever tried reading an IRC log to determine the answer to your question, you probably understand this principle — once you mix anonymized handles in with a many-to-many conversation, you give up quickly.

The asynchronous model fits into everybody's day more nicely and scales much better. I haven't yet seen a question on SO where I said to myself, "This Q&A could have benefited greatly from an increased level of synchronous interaction." (Yeah, that's really how I talk to myself. Wanna fight about it?)


As I mentioned, the big pipe is a beautiful thing. Some nice corollaries are:

One could argue that IRC's Freenode is similar in the virtual channel respect, but logging is certainly not centralized, and listening to many virtual channels simultaneously quickly converges to impossible. Unlike SO's multi-tag view, asking a question in one IRC channel is unlikely to get the attention of people who reside in other channels.

Newsgroups are all-over-the-place decentralized. It's definitely a web 1.0 technology. There's a bunch of services that consolidate information for newsgroups of interest (Google Groups, gmane), but due to the information being replicated all over the web, the page rank for a given Q&A will tend to be weaker as it's divided across the resources and components of the thread. Newsgroups don't tend to play together as nicely as SO tags — it's easy to see how a question like, "What's monkeypatching?" could be asked on comp.lang.python, comp.lang.ruby, and so on, without ever being referred to each other.

On SO, if you tag things properly, information naturally crosses virtual channels and is well indexed for search.


IRC channels tend to get inundated with the same questions over and over, so they make an FAQ to persist a subset of the information that's routinely provided in the channel. Taken to its rational extreme, you could persist all the Q&A information in such a manner, in which case you'd have SO.

Some IRC channels get logged, but I rarely care where the logs are — there's little hope of you finding the answer from the log (as previously discussed). It's also unlikely that the page rank of any given log will be significant. In my IRC experience, you keep your own chat logs if you really care to find the conversations later on. In any case, this is much less elegant than SO's centralized and indexed persistence capabilities.

As I mentioned before, newsgroups have persistence, but it's not well centralized or indexed. Persistence is a moot point if you can't find what you're looking for.

Critical Thinking

Since I'm out of a job as a karma system and NMD doomsayer, I've got to talk about the potential for secondary Armageddon-like effects.

SO doesn't have a significant enough differentiation from refactormycode. Its mission is well differentiated, but it seems like the permitted content on SO is a superset of what can be found on refactormycode. I would consider this kind of Q&A noisy, but it certainly follows the same general format. It's possible the authors are cool with SO engulfing a lot of refactormycode material, but in that case I hope we get some better large code block support. If SO doesn't want it, it should be in the constitution.

I'm concerned about question staleness. Over time we'll see how venerable the Q&As are, but my immediate concern is the plot of views over time: is the drop off in number of views over time for a given question so significant that the return rate cannot overcome initial misconceptions? If misconceptions are introduced later, will users still be watching the thread? There's no "watch this thread" capability in SO for push notification, so to some extent the system expects you to check back at regular intervals to monitor activity on threads. This may be an unrealistic assumption. To be fair, the constitution explicitly states you may re-ask a question if you acknowledge that the other exists, which may prevent this from being such a big deal.

I'm curious as to how the number of non-programming, technical questions has trended over time. Potential problems in this area are alleviated by the constitution and the fact that sufficiently reputable members can close threads, but it's easy to see how there will be an inevitable flow of system administrative questions due to how knowledgeable the constituency is. If the site didn't have such good safeguards, it would easily swallow a whole lot of other Q&A domains that are indirectly programming related.