The FOL-ModelChecker returns a model if there is any.
In the case of infinite models, a finite series of finite "transcendent" models is returned that converges to an infinite model as its limit by increasing the upper bound of the domain just as a series of decimal or rational numbers converges to a number as its limit.
I call a finite model "transcendent" if its interpretations of predicates refer to some object that is not part of the finite domain of that model. In fact, this "transcendent object" will be a natural number i+1 and the finite domain of the model the series of natural numbers 1 to i.
Since the FOL-ModelChecker is based on the FOL-Decider, it may happen that a an infinite model is indicated although the formula is not satisfiable. Therefore, this tool is not quite correct. Yet, this won't happen with time limit <100 seconds.
© Timm Lampert / 201-01-08