Approximate Retrieval from Databases

Three types of imprecision and/or vagueness:
o User does not have precise notion of database contents
o Data stored in the database is imprecise
o Retrieval request is imprecise

Sources of imprecision in the user's model:
o incomplete knowledge of the data model
o imprecise info on database schema and/or instance
o vagueness of user goals
o incomplete knowledge about the interaction tools

How to deal with imprecision in the user's model:
o Browsing
o Heuristic interpretation of user' query
o Example-based techniques

Imprecision in stored data can be dealt with by applying fuzzy sets theory to provide a linguistic description of the stored imprecise data. Fuzzy queries and content-based retrieval allow the user to give imprecise retrieval requests.