True when the catalogue knows the filter's attribute and value
(SEARCH_FILTER_ATTRIBUTES, SEARCH_FILTER_VALUES), compared in normalised form.
One it doesn't know can only have been sent with allowUnknownFilters; a reply
of 0 entries may then mean that the register doesn't know the value either.
True when the catalogue knows the filter's attribute and value (
SEARCH_FILTER_ATTRIBUTES,SEARCH_FILTER_VALUES), compared in normalised form. One it doesn't know can only have been sent withallowUnknownFilters; a reply of 0 entries may then mean that the register doesn't know the value either.