The Mapping System MSv7 works with information stored on internal layers. Layers are kept separately by damage types, but grouped and related to a specific event. Think of a standard loan process where an art work is checked before lending, after arrival, before re-shipping and after arrival back home. If a new damage (or treatment of a damage) needs to be registered, you have the possibility to relate the newly registered damage to an event: you "historize" that particular data entry. Thus you will always know when which alteration to the art work was noticed or treated.
"Complete electronic processing, documentation and historization means that the data can be called up quickly by other users, and all steps can be tracked individually after the event and made available to [...]" (source: http://www.linguee.com/english-german/search?source=auto&query=historization)