A design tool of database conceptual schema is proposed in this thesis. This tool uses E-R model to describe the conceptual schema. The user describes his requirements with natural language. The proposed tool extracts the user's requirement from the natural language descriptions, and constructs the E-R schema incrementally by appending new shema object to existing schema or changing the existing schema. In order to extract the user's requirement from the natural language descriptions, the requirement extracting rules which can resolve the conflict of new user's requirement and existing schema are proposed. The tool uses a set of E-R schema-changing operations for constructing the E-R schema. By using this tool, a user can design a database conceptual schema even though he has no or very little experience on database design and on the knowledge of E-R model.
