We do this by starting with a very basic system, and we build on it either by adding axioms or by enriching the underlying structures. Metric temporal logics are then extended with the notion of time granularity to deal with granular real-time systems. We briefly analyze syntax, semantics, and axiomatization of the resulting metric and layered temporal logics. We mainly concentrate on decidability issues for metric and layered temporal logics. In order to prove the decidability of different classes of layered structures, we exploit tools and techniques borrowed from formal languages and automata theory.
Conclusions provide an assessment of the work and outline current and future research directions.