Qualifying Objects in Classical Relational Database Querying

Database querying by various selection criteria can often confront a major limitation: the difficulty to realize and express precise criteria for locating the information. This happens because people do not always think and speak in precise terms, or they do not have details on the data range. The research community recently proposed a new way to query databases, more expressive and flexible than the classical one. It is about vague queries, for example: “retrieve the persons well paid which live not too far from the office”, of course, formulated in an adequate query language. The main reason to use the vague predicates well paid and not too far is to express more flexibly the user’s preferences and at the same time to rank the selected tuples by a degree of criteria satisfaction. When a precise criterion, like “salary > 500 and distance home-office < 200” is required, it may return an empty list, even if there are a lot of persons having attribute values very close to the specified ones. As well, the same precise criterion may return a complete list of all persons, without any helpful ordering. So, it would be useful to provide intelligent interfaces to databases, able to interpret and evaluate imprecise criteria in queries. AbstrAct