Data model

A model given is a model which describes in an abstract way how the Donnée S in an organization trade are represented, a Information system or a basic Management system of data.

This data model term can have two significances:

  1. a theoretical data model , i.e a formal description or a mathematical model. See also basic Model of data
  2. a data model authority , i.e which applies a theoretical data model (Modélisation of the data) to create a data model authority . See will infra .

Theoretical data model

Components

In general, a theoretical data model described what follows:

  1. Structure of data : it defines how the Donnée S are organized (hierarchical, network, relational, Orienté object).
  2. Integrity of the data : it provides an implicit language or rules for the maintenance of the integrity of the data in the data model authority .
  3. Handling of the data : it provides a language to create, update and remove the data.
  4. Data retrieval : it provides a language to seek the Donnée S.

For example, in the relational Model, all the data are represented by mathematical relations (or, to be precise, a version slightly extrapolated from that). There exists a general language of specification of the constraints (First-order logic), and for handling and the data retrieval, one introduced the relational Algèbre, Tuple calculus and Domain calculus.

One can find additional details on this subject in basic Management system of data.

Levels of concern

A theory of data model generally defines levels of concern. For example, in the method MERISE or the Entity-relation model employed in models (SSADM, SDM/S), one defines levels of concern such as:

  • Conceptual,
  • Logical,
  • Physical.

The contents of the models for each level can vary according to the method.

The Cadre of architecture Zachman also contains these three levels of concern. The data correspond to the " question; what? " (the Cadre Zachman is Holistique, it thus exists five other aspects).

The levels logical and physical appear in DoDAF, like in AGATE. In MODAF, these levels of concern do not appear an obvious way.

Data model authority (application to a specific field)

The Modélisation of the data is the process by which one creates a data model authority by applying a theory of data model. One employs this method to conform to Exigence S or waitings of companies or public agencies.

The needs are generally expressed through a conceptual Modèle for data and/or a logical Modèle of data. These models are then transformed into a Data model physics, which describes the Databases physical employees.

For a specific application, one defines the tables (Objet S, Relation S,…, the Conventions of naming depends on the general model). For example, " is described; client" , " commande" , " article" , as well as the relations between them (" a customer orders articles").

If one uses a relational Modèle, one must define specific whole of Contrainte S (Clé candidate S, Foreign key ), by using the suitable language in accordance with the general model (e.g SQL).

Tools to create the data model of an application

Whereas the simple models of data (those consistent in few tables or objects) can be created “manually”, the more complicated models requires a more systematic approach. In the communautéde modeling of the relational databases, the method of the Entity-relation model is used to establish a data model specific to the field. In the community of the directed programming object, one prefers language UML (Unified Modeling Language) for the creation of data models. In UML, the " diagrams of classe" present many resemblances to the diagrams entity-relation, but the majority of tools UML, like Rational Pink and Embarcadero Describe , do not have the possibility of supporting the conceptual, logical, and physical traceability. Other methods, as Functional dated model and Object role modeling (ORM), describe also subsets or aspects of a data model and applications which are based on him.

Governmental data models

In Europe

The governmental information systems must comprise referential of Interopérabilité. The program ADELE of the French government comprises a general Référentiel of interworking and safety with common data models.

See: Model of given common of ADELE.

In the United States

Today, the division of information and the data-processing Interopérabilité are obtained by the use of Métadonnée S. the United States hold already a great number of Registres of metadata for kingly Fonctions (Justice, defense).

The Department of Defense lays out, in the Cadre of architecture DoDAF, to a Core Architecture Went back Model (CADM).

The US government launched in 2002 the project Federal Enterprise Architecture (FEA), which includes five models, of which a data model of reference (DRM). This model will include Métadonnée S with large scales.

The chief of the Data project Refers American Model, Michael Daconta, is the former head of the center of excellence on the Métadonnée S of the department Homeland Security (internal security).

Michael Daconta is the author of a declaration of independence of the data: Declaration off dated independence

External bonds

  • RFC 3198 - Terminology for management in accordance with the procedures

  • RFC 3444 - On the difference between models in information and data models
  • Data refers model Modèle of reference of the data of the government of the United States

See too

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