‐domains
 ‐essentially abstract datatypes
 ‐in the rdbm context, we aim at decomposing these too into atomic types
 ‐relations can form a domain, with domain specific operations reaching within the objects
 ‐domains have structure which cannot be neglected!
  ‐even general theta‐joins take advantage of the order relation!
  ‐why not take advantage of other operations/structure, or take the existing
   structure more seriously?
   ‐"group by is okay", because it is a device for defining equivalence
    relations and performing set divisions modulo them
   ‐e.g. oracle’s analytic functions are basically lattice iterators for the
    order relation