System of Spheres-based Two Level Credibility-limited Revisions

Two level credibility-limited revision is a non-prioritized operation. When revising by two revision, levels of credibility and one incredibility are considered. sentence at the highest credibility, operator behaves as standard if second then outcome process coincides with contraction negation that sentence. If not credible, original belief set remains unchanged. In this paper, we propose construction for operators based on Grove's systems spheres present an axiomatic characterization these operators.