Each set could be assigned its own category and by combining them into a single database,
one lookup returns a result for each of the four sets.
-* **userdata**: A user-defined field that could be any value except zero.
+* **userdata**: A user-defined value.
For each category, a successful match returns the userdata field of the highest priority matched rule.
+ When no rules match, returned value is zero.
.. note::