  This short paper gives a model for and a proof of completeness of the NRB
verification logic for deterministic imperative programs, the logic having been
used in the past as the basis for automated semantic checks of large,
fast-changing, open source C code archives, such as that of the Linux kernel
source. The model is a colored state transitions model that approximates from
above the set of transitions possible for a program. Correspondingly, the logic
catches all traces that may trigger a particular defect at a given point in the
program, but may also flag false positives.
