Agents use processes of decision and prioritisation to schedule a sequential stream of financial commitments. In order to enable them to do this, the simulation models their ability to remember and foresee income and outgoings. This information then forms the basis for decision. The simplest possible model of budgeting is one in which the flows of income and outgoings are totally uncontrolled by the agent. This basic model is equivalent to a tank of water with uncontrolled inflows and outflows.
Saving is just the amount of water in the tank at any time.
This randomness models unpredictability both within and without the agent, for example, cheques may be cleared in a different order from that in which they were written and unanticipated desires may arise from within. The only measure of wellbeing we shall consider for the moment is survival. The basic model involves three modules, an environment, which generates a series of commitments, for example bills for rent and sensations of hunger, a list of priorities which, in the absence of any decision process is simply sequential, and an account which consists of the current savings. The list of priorities is sequential in the sense that the newest commitments are added to the bottom of the list and commitments are met in order from the top of the list, that is to say, first in, first out. In addition, the simulation involves two processes, that by which newly generated commitments are added to the list of priorities, and that by which commitments are removed from the list of priorities as they are met.