We present two models of hierarchical structured multi-agents, and we describe how to obtain a modal knowledge base from distributed sources. We then propose a computationally oriented revision procedure for modal knowledge bases. This procedure is based on a labelled tableaux calculi supplemented with a formalismto record the dependencies of the formulae. The dependencies are then used to reconstruct the minimal inconsistent sets, and the sub-formulae responsible for the inconsistencies are revised according to well-defined chains of modal functions.