In the early days, one could follow Recent changes on a daily basis, to see if anything had changed. Nowadays watchlists reduce the amount of information to those pages one is interested in.
Many articles are soo long, and have been edited so many times, that the history view is almost useless. If I want to find out when and how the sentence "Overall, the city is relatively flat"in the article [[en:Paris]] has changed over time, I can sit all day and analyze individual diffs.
I think it would be very useful if I could highlight a sentence, paragraph or section of an article and get a reduced history view with only those edits that changed that part of the page. What sorts of indexes would be needed to facilitate such a search? Has anybody already implemented this as a separate tool?