On Ancestral Taxonomy Assignment…

Here’s an esoteric question for all IAs or content strategists –

Assume we have a hierarchical set of categories, naturally progressing from from broader to narrower. For example, one branch goes:

• Vehicles
  • Wheeled Vehicles
    • Motorcycles

Should software provide “assumed ancestral assignment”? Meaning, if you assign a category lower/narrower in the hierarchy, should the assignee (the content object) have an “assumed assignment” to all the ancestor categories as well?

If I assign a content object to “Motorcycles,” should it automatically also be assigned to “Wheeled Vehicles” and “Vehicles”? Or is it just assigned to “Motorcycles” alone, even though basic logic dictates that it’s also a “Wheeled Vehicle” and a “Vehicle”?

If we didn’t do this “assumed ancestral assignment,” we could just depend on forming the proper query – for instance, if we wanted “Wheeled Vehicles,” we could just be sure to search for anything assigned to that category OR BELOW (effectively doing “ad hoc assignment” in our search), which would capture our object assign to “Motorcycles.”

Or should software force an actual category assignment at the UI level or the persistence level? So if someone checks the box for “Motorcycles,” we automatically check the boxes for the two ancestors (again, either in the UI, or behind-the-scenes when persisting the assignment(s) to storage).

Either way, how do we train our editors on the appropriate “level” of assignment? Do we just tell them to assign to the most specific level possible? How do we get them to assign at the right level of specificity and avoid too many questions or quandaries?

This seems like a general problem that has no-doubt been solved, but is there a standard or common practice?