The second author has put forward a theory of incomplete interval probabilities meant to give a common framework to both interval probabilities and openframe bodies of evidence, as obtained by application of the non-normalized open-frame Dempster rule. Below we re-describe this proposal and then compare two possible ways of conditioning" based on the open-frame Dempster rule: namely, we condition the original possibly incomplete knowledge by pooling it with new evidence which assigns certainty to the conditioning event. The idea is trying to build a probabilistic theory which would be able to cope not only with uncertainty and ignorance, but also with forms of contradictoriness, to be included into the description of a possible state of knowledge. Keywords. Open-frame beliefs, Dempster conditioning, incomplete probabilities, interval probabilities.