 Still, the technical reductions do not resolve the semantic question whether sentences are to be evaluated with respect to instants or with respect to intervals, and one may argue that both instants and intervals are needed as mutually complementary. Two-sorted point-interval models were studied in e.g. Balbiani et al. (2011), and more complex models of time have been investigated as well, including models of time granularity (Euzenat and Montanari 2005), which allow for different resolution levels of temporal intervals (e.g. minutes, hours, days, years, etc.), metric and layered temporal models (Montanari 1996), etc.