DBMS > Inroduction > What do you mean by Data Model?

Data Model:

Data models define how the logical structure of a database is modeled by the database architect. It is a description of the objects/entities represented by a computer system together with their properties, relationships and certain constraints that the database should obey. Output of data modeling is diagram that represents the data structure to support a new software application. 

In the context of programming languages, data model sometimes refers as a data structure and in the context of enterprise models it is function models.

Data Modeling Process

Data modeling process involves three MAIN PHASES with different levels of detail: the conceptual data model, the logical data model, and the physical data model.

Conceptual (high-level, semantic) data models: The conceptual level is a way of describing what data is stored within the whole database and how the data is inter-related. The conceptual level does not specify how the data is physically stored. Some important facts about this level are ...

• DBA works at this level.
  
• Describes the structure of all users.
  
• Only DBA can define this level.
  
• Global view of database.
  
• Independent of hardware and software.
  

it is also called entity-based or Object-based data models.

Physical (low-level, internal) data models: Provide concepts that describe details of how the data is actually stored in the database and on the computer hardware.

Implementation (representational) data models(External Level, User Views): Provide concepts that fall between the above two, balancing user views with some computer storage details. A user's view of the database describes a part of the database that is relevant to a particular user. It excludes irrelevant data as well as data which the user is not authorized to access.

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