Question

i am thinking of making a website..
bt how can i make sure that when a user who is asking some question is nt using any abusive language or the message is totally subject oriented..
i m nt talking about spams..i know about captcha and all..
what i am asking is how can i keep an eye on human activity[in this case the messages sent] and at the same time providing the user his complete privacy!

Answer 1

There are curse-word filtering libraries available in most languages, usually complete with the ability to customize the words that are filtered out.

In order to filter spam, there are things like bayesian spam filters which attempt to determine whether a message is spam based on keywords in the response. This really isn’t something you would want to attempt to do yourself.

Another thing to look at is Markov Chains. They are designed to generate strings of seemingly valid text based on the probability that any given word is followed by any other particular word. Using a reverse process you can attempt to determine if a string of text is valid by checking whether the words used are following by other “on-topic” words.
This would be very difficult as well.

In order to keep the privacy of the users, you could use combinations of these three tests to create a threshold. That is, you will examine no messages unless they reach a high curse/spam/off-topic score. At that point, those messages will be manually checked to see if they are appropriate.

There currently is no way to have a 100% automated process that won’t block valid messages and let invalid ones through.