I study php, set the task to expand the hierarchical system consisting of 2 tables "category" ( id , parent_id , name ) and "goods" ( code , name ), Relations in the table "products 2 category" ( id , code ).
It is necessary to expand the system with faceted classification. Each product group (from a hierarchical classifier) is characterized by a set of facets and units of measure for these facets. Can anyone sketch out how these facets will be created or explained?