9th International Conference on Flexible Query Answering Systems (FQAS 2011), Ghent, Belgium, 26 - 28 October 2011, vol.7022, pp.25-36
Uncertainty is modeled by a multibase (db, mu) where db is a database with zero or more primary key violations, and mu associates a multiplicity (a positive integer) to each fact of db. In data integration, the multiplicity of a fact g can indicate the number of data sources in which g was found. In planning databases, facts with the same primary key value are alternatives for each other, and the multiplicity of a fact g can denote the number of people in favor of g.