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ERM |
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The ERM (Entity-Relationship Model) allows to show a large view of modelling.
The goal of this part is to focus on the structure of the information in order to schematize it.
1 - Identify the strong identities
We begin to list the general elements, the strong identities present in the datawarehouse..
2 - Create the relations between each strong entities
There is at leat one relation of N:M type (several to several).
The functional interpretation of each N:M relation allows the creation of new entities that will change the N:M relations to 1:N relations (one to several).
3 - Create the schema with the 1:N relationsz
A central identy will be created: the fact table.
4 -Detail the schema
Each entitty has attributs, details, descriptions.
5 - Schematize the relations between attributs and their entities
This schema allows to have the more detailed view at the relational level in order to review the modelling.
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