This study addresses the limitations of the rigid and simplistic relational structure of the KDC 6th edition’s relative index by systematically analyzing the relationships between index terms. Based on this analysis, a flexible and detailed model for structuring the relationships within the relative index is proposed. The study categorizes these relationships into hierarchical, associative, and equivalence relationships, further subdividing them to capture the complexity of the interactions. The proposed model is implemented using RDF syntax, suggesting the potential for extending the relative index into linked data. This model not only clarifies the complex relationships between KDC index terms but also contributes to the development of a dynamic and adaptable classification system capable of effectively incorporating new information.