  The definition of stable models for propositional formulas with infinite
conjunctions and disjunctions can be used to describe the semantics of answer
set programming languages. In this note, we enhance that definition by
introducing a distinction between intensional and extensional atoms. The
symmetric splitting theorem for first-order formulas is then extended to
infinitary formulas and used to reason about infinitary definitions. This note
is under consideration for publication in Theory and Practice of Logic
Programming.
