Muddiest Point Week 10

I have a question about controlled vocabulary, I realize this might be a little off topic. When a term in a controlled vocabulary is changed, do the indexers use a find and replace to update the term in the indexed documents? If a new term is added, is it possible to go back through a database and add the new term to other documents it might describe without rereading every document?

Not a muddy point, but a comment on Yahoo's old style of categories that was mentioned in class. . . I can remember in late 90's I had submitted a website to Yahoo's search engine. If I remember correctly, I had to select the subjects it fell under.