  We discuss regular and weak solutions to rough partial differential equations
(RPDEs), thereby providing a (rough path-)wise view on important classes of
SPDEs. In contrast to many previous works on RPDEs, our definition gives honest
meaning to RPDEs as integral equation, based on which we are able to obtain
existence, uniqueness and stability results. The case of weak "rough" forward
equations, may be seen as robustification of the (measure-valued) Zakai
equation in the rough path sense. Feynman-Kac representation for RPDEs, in
formal analogy to similar classical results in SPDE theory, play an important
role.
