did you mean ... ?

me and my colleagues are discussing google's correction system. i guess you know it?

(you enter a word and make a (spelling) mistake (aple). google offers you a search of the word without the mistake [did you mean: apple]).

does anyone of you have experience in such algorithms? how do you think does it work (in general)?

we guess it must be something like:
1. search for the entered word and getting the results
2. searching for other words, that 'look' like the entered one (comparing the letters and their place in the word) and getting the results
3. realizing, that another, very similar word, gets much more results
4. offering this word as [did you mean: ...]

what do you think of this? if you do agree, do you know more about step 2 (the comparing of the words)?

their algorithm must be quite strong (did you expect anything else of google?): http://www.google.com/jobs/britney.html

thank you,
m