(Oracle, WAIS, Fulcrum, Architext)
A set of related informations stored in tables. Relational databases are often used to store numerical and factual data. More recently, they have been used to organized text, such a email and notes (e.g. Lotus Notes). Documents that contain fields such as email (subject field, date field, from field) are amenable to be treated by/as a relational database. Indexes by fields can be built. Example of natural language field search query: all emails of isabelle from May 1995 until now