Fuzzy queries in relational medical databases

The importance of information systems in the field of health care has grown considerably within the last decade. Databases containing administrative and medical data are frequently used in health-care environments. Especially relational database systems play an important role in theory and practice. In order to formulate ad-hoc queries to information systems which provide complex information, such as medical data like vitality functions or lab-data, one has to use adequate and powerful query languages, such as SQL. In this paper we present an add-on system for Set, called MetaSQL, which is able to cope with imprecise and complex queries by using a fuzzy knowledge base. In particular, it will be shown how imprecise selection criteria can improve the quality of query results, especially in the medical domain.