  We undertake a study of markets from the perspective of a financial agent
with limited access to information. The set of wealth processes available to
the agent is structured with reasonable economic properties, instead of the
usual practice of taking it to consist of stochastic integrals against a
semimartingale integrator. We obtain the equivalence of the boundedness in
probability of the set of terminal wealth outcomes (which in turn is equivalent
to the weak market viability condition of absence of arbitrage of the first
kind) with the existence of at least one strictly positive deflator that makes
the deflated wealth processes have a generalized supermartingale property.
