Evaluation query answer over inconsistent database with annotations

Abstract

In this paper, we introduce an annotation based data model of relational database that may violate a set of functional dependency. In the data model, every piece of data in a relation can have zero or more annotations with it and annotations are propagated along with queries from the source to the output. With annotations, data in both input data and query answer can be divided into certain and uncertain part down to cell level. It can avoid information loss. To query an annotated database, we propose an extension of SPJ-UNION SQL, CASQL, and algorithms for evaluating CASQL so that annotations can be correctly propagated as the valid set of functional dependency changes during query processing. Last, we present a set of performance experiments which show that time performance of our approach is acceptable, but performance in information preserving is excellent. © 2010 Springer-Verlag Berlin Heidelberg.