By Michael Marshall
LSI is a methodology for automatic document classification. It examines all the words in all the documents of a corpus and calculates similarity measurements for each document or for individual terms. It can gauge very accurately which documents in a corpus are really relevant to a search phrase even if that search phrase does not appear in a document. Measuring relevancy is a key component of a search engineâ€™s ranking algorithm. When search engines use it, LSI can have a significant impact on the ranking of your web pages.