The next YC application deadline approaches, and I thought it would be fun to look at the successful application Muzzammil and I wrote in the summer of 2010. At the time, we were both undergraduates, and we hadn’t yet built our product. I’ll go through our responses one by one.

What is your company going to make?

We described exactly what our product would do.

Taazr detects bugs in live web applications through statistical inference.

Think of a web application as a black box, with its inputs as HTTP requests and its outputs as HTTP response data. After a client instruments her web app with our javascript, Taazr will collect request/response data to build a model of expected behavior. When an “anomalous” response is detected, we notify our client, sending along details about the potentially faulty request/response pair.

Don’t be vague. Going into detail may seem to leave out the “bigger picture,” but I suspect this matters little to the readers at YC. You have the rest of your application to impart a broader vision; for this question talk specifically about what you are going to build.

Please tell us in one or two sentences about the most impressive thing other than this startup that each founder has built or achieved.

It’s often said that YC is all about the founders. Our answer:

Ethan was admitted to CS PhD programs at Stanford, Berkeley, and MIT for research on automatic software development (e.g. automatically finding bugs, fixing bugs, generating test suites).

Muzzammil is a member of the core development team for GuardRails, a secure web application framework, which will be published at USENIX 2011 and presented at RubyNation. He is also the founder of Wahoobooks, a site where U.Va. students can list used textbooks.

We mentioned specific and verifiable achievements, the substance of which implied that we are determined people. You should try to avoid generalities.

Please tell us about the time you most successfully hacked some (non-computer) system to your advantage.

A great answer here can really help you, but it was perhaps our weakest response. Judge for yourself:

A Computer Science degree from U.Va. typically requires that you complete many courses within a variety of unrelated disciplines. Most of our peers must take classes in Physics, Chemistry, and a “fake” humanities listing called Science, Technology and Society. We escaped such requirements through a little-known option to pursue a BA in Computer Science, in place of the Engineering School’s BS. With this degree, we completed the core CS curriculum and any other classes that caught our interest, but we avoided the rigidly defined ABET requirements of the Engineering school. This left us more time to pursue research and hack on web applications.

While Muzzammil and I aren’t totally straight-laced, we couldn’t think of much to say. And that was a strategic error, for a sufficiently devious answer has a great opportunity to stand out. While I like to think that the most clever subversives are the overtly boring ones, that’s not correct so far as this question is concerned. Give a better answer than we did!

Please tell us about an interesting project, preferably outside of class or work, that two or more of you created together. Include urls if possible.

I’d rate our answer here as about average. We’d worked together before, but not on anything terribly impressive.

For a mobile development class, we created a Barefoot Running application1 for the iPhone. The app allows users to report and view the location of glass shards — centralized in an off-site database — and keeps track of speed and distance data throughout a run.

We also jointly created BijectKarma, a community connecting designers and developers2. We had trouble attracting initial users, however, and the site was taken offline.

Perhaps I should give a plug to barefoot running, as clearly that’s the reason we were accepted. Go work on cool things.

How long have the founders known one another and how did you meet? Have any of the founders not met in person?

This one is easy to interpret. Come application time, there’s nothing much you can do to improve your answer.

1.5 years. Ethan was Muzzammil’s TA.

While working on a problem set, Muzzammil mentioned his interest in startups. Ethan asked if he had heard of Y Combinator, which of course Muzzammil had. As it turned out, we were both fishing for potential co-founders.

So yes, you should meet people earlier rather than later. It’s better if you can convey that your founders know each other well.

Why did you pick this idea to work on? Do you have domain expertise in this area? How do you know people need what you’re making?

I like our answer to this one, but with a few caveats.

Finding and fixing software bugs is expensive. Taazr will save companies time and money by identifying bugs and potential fixes in web applications. We chose to work on Taazr primarily due to our familiarly with related research fields, but also because it represents a challenging problem.

Ethan has two years of experience hacking with the Automatic Program Repair (APR) research group at U.Va, where he’s worked with state-of-the-art techniques in program analysis, testing, and statistical debugging. He has published work increasing the efficiency and scalability of APR.

Muzzammil has a year of experience with the GuardRails research group at UVA, where he helped create a secure web framework for Ruby on Rails. His work is published in USENIX 2011 and will also be presented at RubyNation.

More generally, Taazr was inspired by the Cooperative Bug Isolation Project2, in combination with ideas gleaned from our respective research groups at U.Va.

We describe our domain expertise, and slip in evidence that we can get things done. However, we do come off as a bit researchy, which I think is a bit of a risk. Convey expertise through specific accomplishments. You should be perceived as people who know what they are getting into.

What’s new about what you’re making? What substitutes do people resort to because it doesn’t exist yet (or they don’t know about it)?

For us, this was almost a continuation of the previous question.

Uncaught program bugs are expensive, and for this reason, good developers take care in testing their code. However, even the best test suites will not catch all program bugs. Taazr will identify such bugs earlier in the development cycle, and companies will save money that otherwise might have been spent on code maintenance and customer support.

We believe that statistical debugging is uniquely suited to web applications, due to the relative ease with which web apps can be instrumented through lightweight and unobtrusive javascript. While statistical debugging has succeeded in a research context on desktop software, automatically finding bugs in live web applications remains an open industrial problem.

However, our ultimate aim is not just to find bugs in web applications, but also to fix them. This will likely require tighter integration — server-side — between our tools and a developer’s code.

I’d once more levy the “researchy” criticism against our response. An answer to this question will depend upon your product, and I doubt it matters whether your idea is truly novel. As always, clarity is important.

Who are your competitors, and who might become competitors? Who do you fear most?

Another straightforward one.

Coverity and Klocwork also find program bugs, but they don’t target web applications. Moreover, engineers use their products throughout the development process, whereas Taazr operates, automatically, on live production code.

It’s worth noting that we didn’t fully answer this question. I suppose that’s because we are fearless, but I’d recommend a different approach.

What do you understand about your business that other companies in it just don’t get?

Our answer here was weird.

Writing code is much like putting words to paper, an act of creation. When you write, it is important to spell things correctly, but few writers spend much time on this task, for they have spellcheckers. We think that testing should be just as straightforward. It is quite important, but should not monopolize your attention.

Our response is both wrong — I now disagree with it — and confusing. Testing is a bit of a non-sequitur. You should give a real reason why you have insight over your competitors.

How do or will you make money? How much could you make? (We realize you can’t know precisely, but give your best estimate.)

We had no idea how much we could make.

Taazr will charge clients monthly. We see a market opportunity in the tens of millions.

I’m not sure this question matters much, as it’s pretty easy to see how most products might become profitable. If your idea is particularly eccentric, then perhaps a good answer matters more.

Please tell us something surprising or amusing that one of you has discovered. (The answer need not be related to your project.)

This is a fun question to answer, but I don’t think it heavily impacts your application.

You can start small word-memes among family and friends. Choose a word that is fairly obscure (but not obviously so), something like pedantic, sycophant or obsequious. Over a few days, casually inject it into conversation.

Listen throughout the next week. The word will come up with surprising frequency. You can also do this with unique inflections, and distinct rhythms of speech.

You should try to be interesting and clever, I suppose.

The rest of the questions?

Our responses were one-liners which suggested that we had begun market research, but didn’t have any customers. Nothing insightful. But we did receive a follow up question from Robert Morris…

Robert Morris: Why should I believe that this will work?

We gave him a well-grounded but complicated answer, as suits an MIT Professor.

The best evidence probably comes from recent web security research. For instance, Vigna et al. has successfully used anomaly detection to identify security vulnerabilities in web applications. While we are attacking a different goal (identifying bugs, not vulnerabilities), our current work borrows heavily from techniques used successfully in anomaly detection systems.

Since our models will be trained on more detailed user metrics than has traditionally been attempted (e.g. user mouse movements and clicks, as opposed to just HTTP request strings), we see the real question as whether we can distinguish between anomalous user activity (which may signify a bug, or some other issue) and the noise which you would expect in user-based data.

We didn’t receive a follow up question, although it’s unclear whether that’s a good thing.

Concluding thoughts

I hope you found this useful. It was fun to dig through our old application, particularly as we have since gone through a full pivot: Taazr became Proxino. Things change; such is the nature of time, and confidant YC applications.

As final advice, I would focus on brevity and concision in your answers. The people at YC read through quite a lot of these, after all. I’d also keep in mind that ideas are fungible, and people are not. YC cares about the founders. And if you take away anything from this post, it should be that groups with imperfect applications can get into Y Combinator. So be inspired. Best of luck to applicants for the winter batch.