The simplest way to use decision procedures is to evaluate propositional expressions and return Boolean values. However they could also be used in other modes. Probably the most useful of these is to return a list of entities for which a certain property holds.
This is more problematic than propositional evaluation since there may be a large (or even infinite) number of entities for which the property holds. The problem can be overcome in a number of ways each of which produces a different functionality, so it may be useful to define a variety of decision procedure operations on predicate expressions. For instance one may want to refer to a unique entity satisfying a condition and so return either a single object or values none and many if the property does not identify a single entity. Alternatively one may wish to obtain a list of all entities for which the property holds.