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4.9 Elementary Method "Data Navigation Modeling" (DNAV)  

  4.9 Elementarmethode "Data Navigation Modelling" (DNAV)

Contents  
  • 1 Identification/Definition of the Method
  • 2 Brief Characteristic of the Method
  • 3 Limits of the Methods Application
  • 4 Specification of the Methods Allocation
  • 5 Interfaces
  • 6 Further Literature
  • 7 Functional Tool Requirements
  • 1 Identification/Definition of the Method

    /Martin, 1987/ chap.12

    2 Brief Characteristic of the Method

    Objective and Purpose

    Together with the logical database modeling (DB modeling) the method Data Navigation Modeling (DNAV) is used to generate a database management system (DBMS) oriented data structure (see method LOGM - Logical DB Modeling) from an ER - E/R Modeling. Data navigation modeling is indispensable for the generation of efficient hierarchical and network-oriented database structures.

    Means of Representation

    The results of the Data Navigation Modeling are represented with data navigation diagrams. In this connection, E/R submodels are graphically completed by type and order of the accesses of the relevant applications.

    Operational Sequence

    Based on (normalized) E/R models it is analyzed in which order and mode (reading, writing, updating) the data accesses of the relevant applications to the E/R models are realized. Furthermore, frequency and priority of these applications must be analyzed and recorded.

    3 Limits of the Methods Application

    - not applicable -

    4 Specification of the Methods Allocation

    No. Activity Description
    4.1 SD5.1 - Description of SW Component/ Module/ Database In order to generate a database schema for existing or respectively commercially available data base systems the method must be applied together with LOGM - Logical DB Modeling and NORM - Normalization. Parameters referring to the physical storage and available in the database schemas of individual database systems can not be defined with DNAV, LOGM - Logical DB Modeling, and NORM - Normalization alone.

    Together with LOGM - Logical DB Modeling and NORM - Normalization, DNAV covers that part in subproduct SW Design (Database).Schema Definition that refers to the DBMS-oriented data structure. The complete schema definition also requires the specification of external keys and indices as well as integrity conditions and possibly also views. Furthermore, DBMS-specific storage parameters and all data elements must be completely defined.

    5 Interfaces

    No. Interface Observation Information in Annex 1
    5.1 DNAV-ER Data Navigation Modeling is based on E/R models. Data navigation diagrams are generated by means of overlapping E/R diagrams with qualified and quantified access paths.

    Recommendation:
    It is recommended to normalize the E/R models prior to applying DNAV.

    4.6 Interface DNAV-ER
    5.2 DNAV-PCODE Mode and order of the data accesses defined in the DNAV method have to be adjusted to the operational sequence description in PCODE - Pseudocode. 4.7 Interface DNAV-PCODE

    6 Literature

    /Batini, 1992/ Conceptual Database Design
    /Martin, 1987/ Diagramming Standards for Analysts & Programmers
    /Vetter, 1990/ Aufbau betrieblicher Informationssysteme
    /Vossen, 1988/ Datenmodelle, Datenbanksprachen und Datenbank-Management-Systeme

    7 Functional Tool Requirements

    SSD11 - Supporting Database Specification

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