On Similarity Between Preferential Structures

M-bisimilarity of the preferential structure and the equivalence of preferential models have been studied in this thesis. The expression ability of Boolean combinations of conditional assertions also has been discussed. The main achievement of this thesis includes: (1) This thesis has introduced a notion of M-bisimilarity, and established the relation between M-bisimilarity and the equivalence of preferential models applying the technology of standard translation, and has provided the characterization for the equivalence of preferential models in terms of M-bisimilarity. (2) We have studied the expression ability of Boolean combinations of conditional assertions, and provided the characterization for the fragment of first-order sentence, which are equalient to some Boolean combinations of conditional assertions . (3) We have established the characterization for the classes of preferential structure can be expressed or limited expressed based on Boolean combinations of conditional assertions.