This is what I'm trying to do: HasPersistence - an Interface class which implements things like WriteToDisk(), ReadFromDisk() B isA A C isA A, but also implements HasPersistence My solution in R.oo is to have a root class called A which implements IsPersistent() by returning FALSE, but is overrideable by C to return TRUE. C will also implement WriteToDisk() and ReadFromDisk(). This solution will work, but is kludgy, because it is not directly obvious that IsPersistent(), WriteToDisk(), and ReadFromDisk() go together in a conceptual HasPersistence. Is there a more R.oo-clean-way of multiply inheriting like this, so if someone else reads my code, the concept of HasPersistence is more obvious? In other words, could I actually have a HasPersistence class and have C inherit from A and implement HasPersistence also? - Ken -- View this message in context: http://www.nabble.com/Need-Help-with-R.oo-and-%22multiple-inheritance%22-tp23109913p23109913.html Sent from the R help mailing list archive at Nabble.com.