Gruber writes: “An ontology…should offer a conceptual foundation for a range of anticipated tasks, and the representation should be crafted so that one can extend and specialize the ontology monotonically”, i.e. without revision of the existing definitions. Only if this holds, one can propagate an extensible ontology as an ISO standard. To our opinion this is both, an ontological and an epistemological principle:

From the epistemological side, monotonicity under the addition of knowledge which is not in contradiction to previous one, is needed on both, the categorical and the factual level; else the integration of facts as they come in over time becomes a non-scalable task. On the other side, it is an ontological question, because the notion of what is in contradiction and what is not, is grounded in the domain conceptualisation

Monotonicity can be regarded at least on three levels, classification, attribution (properties), and modelling constructs.