Simple because it uses a left shift and or. Only have to store 1 character of test at one moment. Karp Rabin String matching take the search string and encode it to a number. Summary see web page Ranking and Relevance Ranking search results to clarify what's relevant and important. Query expansion uses additional information asked or received that allows the computer more information about the potential answer.
More important terms have heavier weights.
Usage is similarly to spell checkers Factor from SVD related to factor analysis. Singular Value Decomposition. Attribute value pair publish dates added to a list of documents that provides a decreasing weight or relevance. The vector space model has been around since the 60s and 70s. Mentioned in the SALT75 article.