A data model is "a model of the data to be described and processed in an application area (e.g. data from the production area , accounting or the entirety of company data ) and their relationships to one another."
In computer science , especially in the development of information systems , data models and the activities carried out to create them ( data modeling ) are used to find and define the structure for the data to be processed in the systems (in particular for the data to be stored).
Types of data models
Data models are created in successive stages, the results of which are generally differentiated as follows:
- Conceptual data model : Implementation-independent model, e.g. B. an ER diagram (most commonly used) or a UML diagram ; The objects of the real world (in the relevant context) that are to be mapped in the database and the relationships between these objects are modeled.
- Logical data model : mapping of the conceptual database schema to the rules of the database management system to be used , e.g. B. acc. the relational data model in which all data is stored in tables.
- Physical data model : Contains further specifications required or appropriate for technical operation, e.g. B. Index structures for access optimization. These remain hidden from the database user.
The model graduation shown above, which is based on the development process, and especially the names of the models are not used and named uniformly in practice. For example, other terms are often used in the literature, in publications and in common parlance; In particular, only the term “data model” is often used.
The following terms are used to describe certain types of “data model types” and the like. a. differently designated.
(in brackets: synonyms for the levels 1–3 described above)
- For (1,2,3): data model, object model
- For (1,2): logical data model
- For (1): Semantic data model ; conceptual (conceptual), technical data model or database schema; Information structure; Information model; informal description
- For (2): database model
- For (3): data schema, database schema
The terms semantic data model, data model, database model denote in the DB literature, z. B. if not the above. Model gradations (as a result of the modeling), but rather the language or the theoretical basis according to which the models are created.
Method-specific terms are also used in language (such as ER model , class model, class diagram ), which, however, do not result from the process-oriented gradation made here, but from the modeling methodology used.
- ^ Gabler Wirtschaftslexikon
- ↑ Pernul, Unland databases in the company 
- ↑ Saake / Sattler / Heuer: Database Concepts and Languages. 3rd edition: p. 122 ff.
- ^ Kemper / Eickler: Database systems. 6th edition. P. 32 ff.
- ↑ Elmasri / Navathe: Fundamentals of Database Systems. 5th edition. P. 59 ff.
- ↑ Kifer / amber / Lewis: Database system. 2nd Edition. P. 31 ff.