In a hierarchical model, data is organized into a tree-like structure, implying a single parent for each record. Think of a relational database as a collection of tables, each with a schema that represents the fixed attributes and data types that the items in the table will have. And even if the name is the … A sort field keeps sibling records in a particular order. This is also the logical structure of contemporary database indexes, which might only use the contents from a particular columns in the lookup table. Hierarchical structures were widely used in the early mainframe database management systems, such as the Information Management System (IMS) by IBM, and now describe the structure of XML documents. Different entities are related using relationships. The named columns of the relation are called attributes, and the domain is the set of values the attributes are allowed to take. ,