A more-like-this query occurs when the user can click on a particular document in the result list and tell the search engine to find documents that are similar to this one. Describe which low-level components are used to answer this type of query and the sequence in which they are used.

Document filtering is an application that stores a large number of queries or user profiles and compares these profiles to every incoming document on a feed. Documents that are sufficiently similar to the profile are forwarded to that person via email or some other mechanism. Describe the architecture of a filtering engine and how it may differ from a search engine.