ABSTRACT
Users intuitively know which documents are relevant when they see them. Formal relevance assessment, however, is a complex issue. In this entry relevance assessment are described both from a human perspective and a systems perspective. Humans judge relevance in terms of the relation between the documents retrieved and the way in which these documents are understood and used. This is a subjective and personal judgment and is called user relevance. Systems compute a function between the query and the document features that the systems builders believe will cause documents to be ranked by the likelihood that a user will find the documents relevant. This is an objective measurement of relevance in terms of relations between the query and the documents retrieved—this is called system relevance (or sometimes similarity).
