The product information can be practically stored and managed, and also queried when we use a relational database. We need to develop a special indexing scheme in order to process the queries to ask for the semantic relationships of the product information. Such semantic relationships include ISA or taxonomy relationships that have the transitive properties. In this paper, we propose an index scheme to effectively process those queries with the transitive property. The proposed index scheme is based on a numbering scheme that has relatively low update cost.