zmień kontrast font size: A A A
rss polski
you are at >> basics >>database models

Models of databases

Conceptual model

look at the data as whole, the most stable model, it should be the basis on which to build processing of data

Internal model, low-level

- it describes way to store data in computer memory and presents formats of records or paths, such models are the addressing methods , chain and ring structures

Hierarchical model

The model includes two data structures - types of records - relations parent - child Every element known as a record can participate as a child at only one combination of records and in the role of parent in any number of links Child record can not exist without the parent record The market operation is a record

Network model

The model includes two data structures - Types of records - Types of collections Each record can simultaneously takes part in many combinations of records relationship results in many. Such record may simultaneously and repeatedly experiences as a parent and as a child. Combinations are made by special records named as clamp The market operation is a record

Object model

There is no specified definition of object-oriented databases The model is based on concepts such as: - Class - Object - Generalization - Abstraction - Inheritance Objects have methods

Semantic model

Similar to the object model focuses on the abstraction of structure, rather than on abstraction of action

Deductive model

Based on formal logic Elements which are used : - predicates - Arguments Predicates and arguments make up asertion (sentence), which can take the value of the "true" or "false" It is often based on Datalog language.

Post-relational model

Relational model extended to object-orientated elements. There are no strict definition - for databases performing post-relational model there are implementations which "are no longer relational, but yet they are not object-oriented "

Relational model

The basis of this model has become a work published by E.F. Codd in 1970. In this paper, "Relational logical model for large data banks" Codd presented the assumptions of relational database model. In 1990 Codd published the article "Relational model of database management: version 2 ", extending previous work RMD is based on the algebra of relations The basic elements of the model are: - Relations - Ties [ wróć na górę strony ]