A database model is an amalgamation of concepts to describe the structure of a database. It captures the information structure of an application - not the information (the data) itself. The structure of a database integrates the data types, conditions and relationships to describe as well as store the data. Database models also formulate the generic services of databases. Basic requirements for a database model are the support of persistence, quantity, reactivity and integrity.
Database systems based on data models and database models
Database systems can be based on various data models or database models. A data model is a collection of concepts and rules describing the structure of a database, thus realizing a framework according to which information is stored. Database models belong to the category of computer science models and are also called concrete models or implementation models. Database models can be used in a very general way and are therefore not limited to spatial tasks.
Database models depend on the database management system, through which the generic services are also provided: The creation of databases, the storage, modification and deletion of data, the querying of the database and a management of users, accesses and access rights.
The semantics of database models
Thus, a database model also describes the semantics of declarations and expressions of the database language and thus corresponds to an abstract model of the static and dynamic semantics of a programming language.
Essential characteristic features of a database model are:
Quantity A large stock of information is managed by the database, but it can only be fixed at the time the database is designed. Over the lifetime of a database, the stock of information varies dynamically.
Reactivity Due to the integration of an application into an information-processing process, e.g. business process, a database is equally integrated into an environment. The database updates its information stock immediately after the arrival of information, responds to explicit queries and autonomously triggers necessary activities.
Integrity Integrity conditions are maintained in all cases. They can refer to the persistent information stock of the database as well as to incoming and outgoing information.
Database models with characteristically common properties of related database models are grouped into database model families - relational database models are an example.
A basic model is the entity-relationship model (also: ER model or ERM). From this most well-known graphical tool for the design of databases, other well-known models such as the relational, the hierarchical and the network model can be derived. However, the ER model is also used in other areas of computer science for modeling real sections. It is not subject to dependence on a data model, nor to the limitations of a particular data model imposed by their implementation.
Major database models are: Hierarchical database model, Network database model, Relational database model, Object-oriented database model and Object-relational database model.