The paradigm of disjunctive logic programming (DLP) enhances greatly the ex- pressive power of normal logic programming (NLP) and many (declarative) semantics have been defined for DLP to cope with various problems of knowledge representa- tion in artificial intelligence. However, the expressive ability of the semantics and the soundness of program transformation for DLP have been rarely explored. This paper defines an immediate consequence operator T~G_P for each disjunctive program and shows that T~G_P has the least and computable fixpoint Lft(P). Lft is, in fact, a program transformation for DLP, which transforms all disjunctive programs into negative pro- grams. It is shown that Lft preserves many key semantics. Including the disjunctive stable models , well-founded model, disjunctive argument semantics DAS, three-valued models, etc.
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