ZURÜCK Queries

Queries are constructed using attribute - value pairs like q=(t,t1) . For this simple query the result set is Dq:=Dt,ti

Complex queries are constructed by combining queries with the operators AND and OR as well as the use of the operator NOT:

(t,t1) AND (s,s1) denotes the intersection Dt,t1Ds,s1 of result sets, (t,t1) OR (s,s1) denotes the disjunction Dt,t1Ds,s1 of result sets and the unary Operator NOT (t,t1) denotes the complement D\Dt,t1 of a result set. In general NOT is used only together with AND: it excludes documents with a specific attribute value.

These operations can be applied as well to result sets of complex queries, leading to rather complex descriptions of sets of documents.


© 1998 / HTML-Version 17. 11. 1998: R. Ferber