  Several notions of conformance have been proposed for checking the behavior
of cyber-physical systems against their hybrid systems models. In this paper,
we explore the initial idea of a notion of approximate conformance that allows
for comparison of both observable discrete actions and (sampled) continuous
trajectories. As such, this notion will consolidate two earlier notions, namely
the notion of Hybrid Input-Output Conformance (HIOCO) by M. van Osch and the
notion of Hybrid Conformance by H. Abbas and G.E. Fainekos. We prove that our
proposed notion of conformance satisfies a semi-transitivity property, which
makes it suitable for a step-wise proof of conformance or refinement.
