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Annex 1  
4.6 Interface DNAV-ER  

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

    The interface corresponds to type "information transmission from one basic method to another in sequential order". The information is transferred from ER - E/R Modeling to DNAV - Data Navigation Modeling.

    Data navigation diagrams as the result of DNAV method are created by adding qualified and quantified access paths to the E/R diagrams. Therefore, DNAV requires stable E/R models. By adding (planned) qualified and quantified access paths to the E/R diagrams the (planned) accesses to data in the database (based on the E/R diagrams) of the corresponding database system are defined.

    2 Example

    Figure 4.8
    Figure 4.8: Example Interface DNAV-ER

    Explanation of the Example:

    The entity types of the E/R diagram are-as shown in the data navigation diagram-first accessed by reading A, then accessed by reading B, and finally accessed by updating C. In this connection, the information in the data navigation diagram can still be improved via the number and the time intervals of the accesses.

    3 Tool Support

    The interface is supported by some of the commercially available tools, i. e. in that way that information about mode and frequency of accesses as well as entry points of accesses can be listed in the description of the E/R models. These are used by the tools to generate DBMS-oriented data structures.

    4 Literature

    /Martin, 1987/ Chap. 12 contains examples for the generation of data navigation diagrams.

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