  We propose a way of reasoning about minimal and maximal values of the weights
of transitions in a weighted transition system (WTS). This perspective induces
a notion of bisimulation that is coarser than the classic bisimulation: it
relates states that exhibit transitions to bisimulation classes with the
weights within the same boundaries. We propose a customized modal logic that
expresses these numeric boundaries for transition weights by means of
particular modalities. We prove that our logic is invariant under the proposed
notion of bisimulation. We show that the logic enjoys the finite model property
and we identify a complete axiomatization for the logic. Last but not least, we
use a tableau method to show that the satisfiability problem for the logic is
decidable.
