What is Data Dependence in Database Systems?

Data dependence is the way in which the data is organized in secondary storage, and the technique for accessing it, are both dictated by the requirements of the application under consideration, and moreover that knowledge of that data organization and that access technique is built into the application logic and code.

Let’s have a file EMPLOYEE, indexed on field "Emp-No". In an older system, the application will know the fact that the index exists, and also knows the file sequence as defined by that index, and the internal structure of the application will be built around that knowledge. So, clearly such an application is data-dependent because it is impossible to change the storage structure (i.e., how the data is physically stored) or access technique (i.e., how it is accessed) without affecting the application, probably drastically.