It is known that Metric Temporal Logic (MTL) is strictly less expressive than the Monadic First-Order Logic of Order and Metric (FO[<, +1]) when interpreted over timed words; this remains true even when the time domain is bounded a priori. In this work, we present an extension of MTL with the same expressive power as FO[<, +1] over bounded timed words (and also, trivially, over time-bounded signals). We then show that expressive completeness also holds in the general (time-unbounded) case if we allow the use of rational constants $q \in \mathbb{Q}$ in formulas. This extended version of MTL therefore yields a definitive real-time analogue of Kamp's theorem. As an application, we propose a trace-length independent monitoring procedure for our extension of MTL, the first such procedure in a dense real-time setting.

@article{paperbot793,
  title = {On the Expressiveness and Monitoring of Metric Temporal Logic},
  author = {Hsi-Ming Ho and Joël Ouaknine and James Worrell},
  journal = {Logical Methods in Computer Science},
  volume = {Volume 15, Issue 2},
  year = {2019},
  doi = {10.23638/lmcs-15(2:13)2019}
}