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Annex 1  
4.12 Interface ER-NORM  

Contents  
  • 1 Characterization of the Interface
  • 2 Example
  • 3 Tool Support
  • 4 Literature
  • 1 Characterization of the Interface

    The interface corresponds to type "direct integration of another basic method at a certain point of the operational sequence of the corresponding method". In the ER - E/R Modeling, the integration of the NORM - Normalization is realized when completing the entity types with attributes. A detailed description can be found in /Date, 1990/ and /Vetter, 1990/, as well as in /Dutka, 1989/.

    2 Example

    Figure 4.16
    Figure 4.16: Normalization: ARTICLE

    In the example shown above, an article can have several prices (e. g. in case articles are taken on a large scale the price per article may be less). By adding attribute PRICE to entity type ARTICLE, the 1st normal form is violated (multiple attribute). Therefore, a new entity type, i. e. PRICE, must be created by means of the normalization which is linked with entity type ARTICLE by a (1:N) relation type.

    3 Tool Support

    The interface is supported by some of the tools by checking the relations between the attributes of an entity type (e. g. in a screen dialog). In case a normal form is violated, the tool may automatically realize a normalization on request via the creation of new entity types plus the corresponding relation types and keys.

    4 Literature

    /Date, 1990/ Chap. 2.1 handles the normalization in connection with relational databases
    /Dutka, 1989/ Handles the entire range of the normalization
    /Vetter, 1990/ Chap. 4 handles the normalization in connection with the conceptual database design

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