### 3.2.1.2: Queries

Queries are constructed using
*
attribute
- value pairs* like *q=(t,t*_{1}) . For this
*
simple
query* the result set is *D*_{q}:=D_{t,ti}

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

*(t,t*_{1}) AND *(s,s*_{1}) denotes
the intersection *D*_{t,t1}D_{s,s1} of result sets, *(t,t*_{1}) OR *(s,s*_{1}) denotes
the disjunction *D*_{t,t1}D_{s,s1} of result sets and the unary Operator
NOT *(t,t*_{1}) denotes the
complement *D\D*_{t,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