Abstract:
A knowledge base is maintained by modifying its conceptual model and
by using those modifications to specify changes to its implementation. The
maintenance problem is to determine which parts of that model should be checked
for correctness in response a change in the application. The maintenance problem is
not computable for first-order knowledge bases. Two things in the conceptual model
are joined by a maintenance link if a modification to one of them means that the
other must be checked for correctness, and so possibly modified, if consistency of the
model is to be preserved. In a unified conceptual model for first-order knowledge
bases the data and knowledge are modelled formally in a uniform way. A
characterisation is given of four different kinds of maintenance links in a unified
conceptual model. Two of these four kinds of maintenance links can be removed by
transforming the conceptual model. In this way the maintenance problem is
simplified.
