 There are also less general models that offer templates for understanding the reasons underlying preferences. For instance, the multiple criteria decision framework (see, for instance, Keeney and Raiffa 1993) takes an agent’s overall preference ordering over options to be an aggregate of the set of preference orderings corresponding to all the pertinent dimensions of value. Under certain assumptions, the overall or aggregate preference ordering is compatible with EU theory. One might otherwise seek to understand the role of time, or the temporal position of goods, on preferences. To this end, outcomes are described in terms of temporally-indexed bundles of goods, or consumption streams (for an early model of this kind see Ramsey 1928; a later influential treatment is Koopmans 1960). There may be systematic structure to an agent's preferences over these consumption streams, over and above the structure imposed by the EU axioms of preference. For instance, the aforementioned authors considered and characterised preferences that exhibit exponential time discounting.