Are applied questions off-topic?

Question

I wanted to raise this question based on the discussion here. An example would be "What are some real world applications for genetic algorithms?"

The decision here should be added into our FAQ.

Answer 1

There seems to be quite a bit of interest in answering some applied questions. (I've answered some myself.) After I commented that http://cstheory.stackexchange.com/questions/2050/approximation-algorithms-for-maxsat was off topic, Peter Shor replied:

In the '80s and '90s, at many universities, theoretical computer science was very unpopular and looked down upon by the rest of computer science because it was viewed as unconnected to practice. Eventually, Google and other successes convinced them that we were worth talking to. Let's please not close off the lines of communication from the other side now, after having worked so long to open them. That would be very bad for the field, not to mention the TCS job market.

Is there a consensus that heuristic algorithms for rigorously defined problems are on-topic, even if we can't prove anything about them? Should we distinguish methods with theoretical partial results (such as branch and bound, which is easily proven correct albeit potentially exponential) from methods with very little theory (such as genetic algorithms)?

Answer 2

Here's an example of an applied question that's not off topic:

I work in area X and we are trying to model the behaviour of geegaws under severe heat stress. We've formulated it as the following problem and were wondering if there was anything known about this problem.

Here's an example that is on the border:

I work in area X and want to model geegaws under heat stress. How can I do it ?

Here's an example that is off topic:

I work in area X and we have this red and green geegaw that's behaving strangely when we heat it up to 150 F in 50% humidity. How do I explain this ?