Principle of Unity of Idea in a Catalogue Code

The helpfulness of distinguishing between work in the idea plane and in the verbal plane is stated. After listing the structural elements in a catalogue code, the rule-level, the chapter-level, and the part-level of the Principle of Unity of Idea are examined and the qualities necessary in the idea plane and in the verbal plane are listed. In the light of these principles, a comparative study of Rule 58 of ALA 1908 and the corresponding rules of the other codes is made, indicating the impact, if any, received by any code from earlier codes.