Vivification Explained

Vivification is an operation on a description logic knowledge base to improve performance of a semantic reasoner. Vivification replaces a disjunction of concepts

C₁\sqcupC₂\ldots\sqcupC_n

by the least common subsumer of the concepts

C_1,C_2,\ldotsC_n

The goal of this operation is to improve the performance of the reasoner by replacing a complex set of concepts with a single concept which subsumes the original concepts.

For example, consider the example given in (Cohen 92): Suppose we have the concept

rm{PIANIST(Jill)}\veerm{ORGANIST(Jill)}

. This concept can be vivified into a simpler concept

rm{KEYBOARD-PLAYER(Jill)}

. This summarization leads to an approximation that may not be exactly equivalent to the original.

An approximation

Knowledge base vivification is not necessarily exact. If the reasoner is operating under the open world assumption we may get surprising results. In the previous example, if we replace the disjunction with the vivified concept, we will arrive at a surprising results.

First, we find that the reasoner will no longer classify Jill as either a pianist or an organist. Even though

rm{ORGANIST}

and

rm{PIANIST}

are the only two sub-classes, under the OWA we can no longer classify Jill as playing one or the other. The reason is that there may be another keyboard instrument (e.g. a harpsichord) that Jill plays but which does not have a specific subclass.

References

Cohen, W.W., Borgida, A., Hirsh, H., Computing Least Common Subsumers in Description Logics, In: Proc. AAAI-92, AAAI Press/The MIT Press, 1992, pages 754—760. Web site: citeseer . 26 January 2008 . 19 February 2008 . https://web.archive.org/web/20080219014942/http://citeseer.ist.psu.edu/cohen92computing.html . live .
Baader, F., Kusters, R., Wolter F., Extensions to Description Logics. In F. Baader, D. Calvanese, D. McGuinness, D. Nardi, and P.F. Patel-Schneider, editors, The Description Logic Handbook: Theory, Implementation, and Applications. Cambridge University Press, 2003. Web site: citeseer . 26 January 2008 . 12 June 2008 . https://web.archive.org/web/20080612162236/http://citeseer.ist.psu.edu/baader03basic.html . live .