A structural model defines the data that can be stored and retrieved for a database. It provides the following:
Structure. A model specifies the structure of a database. The structure lists the data elements and the relationships among groups of them.
Constraints (business rules). A model constrains the data that can be stored. For example, a frequent flyer account normally pertains to one customer; a model can note this, and a database can enforce it. The constraints in a model become constraints in a database. Constraints enforce many of the rules of a business, thereby reducing errors and simplifying implementation. Modeling provides a way to understand critical business rules, capture them, and drive them into the finished application.
Potential for computation. A model is a blueprint for the questions that can be asked and how they can be formulated. Much application logic consists of traversals of a model and the corresponding database structure to read or modify the data elements.