Currently, facetable model items are defined by a method which is different on writing indexation of the model item and on reading the model item.

It should be the same method which defined if the model item is facetable or not, and it should not be so arbitrary: currently it corresponds to: type is content or user or boolean or has an enumerator, and that's it!

For writing, search for _dv, for reading, take a look to isFacetable() method.