Cours DATA WAREHOUSE

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Datawarehouse

Le lieu de stockage intermédiaire des différentes données en vue de la constitution du système d'information décisionnel est appelé entrepôt de données (en anglais datawarehouse).

Le datawarehouse est ainsi le lieu unique de consolidation de l'ensemble des données de l'entreprises. Le créateur du concept de DataWareHouse, Bill Inmon, le définit comme suit :

« Un datawarehouse est une collection de données thématiques,
intégrées, non volatiles et historisées pour la prise de décisions. »

Ses principales caractéristiques sont donc les suivantes :

* Le datawarehouse est orienté sujets, cela signifie que les données collectées doivent être orientées « métier » et donc triées par thème
* Le datawarehouse est composé de données intégrées, c'est-à-dire qu'un « nettoyage » préalable des données est nécessaire dans un souci de rationnalisation et de normalisation
* Les données du datawarehouse sont non volatiles ce qui signifie qu'une donnée entrée dans l'entrepôt l'est pour de bon et n'a pas vocation à être supprimée
* Les données du datawarehouse doivent être historisées, donc datées

Datamart

Le terme Datamart (littéralement magasin de données) désigne un sous-ensemble du datawarehouse contenant les données du datawarehouse pour un secteur particulier de l'entreprise (département, direction, service, gamme de produit, etc.). On parle ainsi par exemple de DataMart Marketing, DataMart Commercial, ...


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