• previously, the complete thing (with all of its features) were validated against all submodels
• this could be potentially very CPU intensive
• even if not much was changed within a PATCH or MergeThing command, this wasted a lot of resources
• the new approach only validates parts which were changed in the "Merge" command

E.g.:

• if an attribute was modified, all of the attributes are validated
• if part of a feature was modified, all properties of that feature are validated
• if all features were modified, all properties of all features are validated (but then PATCH is not really an optimisation compared to using PUT)
• special case: if the thing's definition was updated, the complete thing is validated as all parts have to be valid according to the updated definition