Currently the approach is to use an ontology. There are free onto-editors such as Protege. "Onto" refers to everything. A common practice is to classify additio

Currently the approach is to use an ontology. There are free onto-editors such as Protege. "Onto" refers to everything. A common practice is to classify additions to knowledge either with a classifier or manually. The potentially lost knowledge is the unclassied remains. So we include a bag called "undecided". It can be just one per system or it can be many scattered throughout the ontology.