The raise of extension set provides reasonable logical foundation for the automatic solving of contradiction problem. This paper views contradiction as an unsatiable concept, an unrealizable action or an item that can't meet the satisfaction of a certain concept, analyzes a representation language in face of contradiction problem, which is, a new extension description logic--ALC D-ES . Syntax definition, semantic explanation and reasoning algorithm Tableau D-ES are given in details, which lay

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... e theoretical foundation for the automatic solving method of contradiction problem based on extension description logic reasoning.