Categorizing Words and Category Values

Question

We were set an algorithm problem in class today, as a \"if you figure out a solution you don\'t have to do this subject\". SO of course, we all thought we will give it a go.

Answer 1

You could implement a learning algorithm to do this using a monte carlo method and human feedback. Have the system randomly categorize words, then ask you to vote them as "match" or "not match." If it matches, the word is categorized and can be eliminated. If not, the system excludes it from that category in future iterations since it knows it doesn't belong there. This will get very accurate results.

This will work for the 100 word problem fairly easily. For the larger problem, you could combine this with educated guessing to make the process work faster. Here, as many people above have mentioned, you will need external sources. The google method would probably work the best, since google's already done a ton of work on it, but barring that you could, for example, pull data from your facebook account using the facebook apis and try to figure out which words are statistically more likely to appear with previously categorized words.

Either way, though, this cannot be done without some kind of external input that at some point came from a human. Unless you want to be cheeky and, for example, define the categories by some serialized value contained in the ascii text for the name :P

Answer 2

This sounds like you could use some sort of Bayesian classification as it is used in spam filtering. But this would still require "external data" in the form of some sort of text base that provides context.

Without that, the problem is impossible to solve. It's not an algorithm problem, it's an AI problem. But even AI (and natural intelligence as well, for that matter) needs some sort of input to learn from.

I suspect that the professor is giving you an impossible problem to make you understand at what different levels you can think about a problem.

The key question here is: who decides what a "correct" classification is? What is this decision based on? How could this decision be reproduced programmatically, and what input data would it need?

Answer 3

Fire this teacher.

The only solution to this problem is to already have the solution to the problem. Ie. you need a table of keywords and categories to build your code that puts keywords into categories.

Unless, as you suggest, you add a system which "understands" english. This is the person sitting in front of the computer, or an expert system.

If you're building an expert system and doesn't even know it, the teacher is not good at giving problems.