Household electrical appliances should be designed to satisfy safety standards. An expert system is implemented to support the design of household electrical appliances. The general-purpose expert system shell, ART-IM which is running under MS-DOS environment, is used to construct the knowledge-base. The source of knowledge is the EN 60 335-1 that is British standard specification for safety of household and similar electrical appliances. This thesis is focused on the methodology of knowledge acquisition from existing documents such as regulatory texts or codes that have systematic and normative structure.