|4.23 Elementary Method "Logical DB Modeling" (LOGM)|
Method Logical DB Modeling (LOGM) is comprised of the application of a rule system used to transform an ER - E/R Model into a database management system (DBMS-) oriented data structure. The term DBMS-oriented data structure refers to hierarchical, network-oriented or respectively relational data structures.
Database schemas of available database systems not only represent the data of an application from a user-level aspect but also have to consider the access and performance aspects in connection with the data organization. These particularly depend on the quantity structure of the data, on the access logic and access frequency of the applications as well as on the technical functionality of the particular database system.
Means of Representation
In hierarchical DBMS, the results are represented in database records that are arranged as trees, in network-oriented DBMS the results are represented in records arranged as networks, and in relational DBMS they are represented in form of tables.
Based on E/R models, DBMS-oriented data structures are generated with the help of the Logical DB Modeling method. The rule system predominantly depends on the target database system, e. g. one for a hierarchical database system can thus be essentially different from that for a relational database system. After the logical data modeling, DBMS-oriented data structures have also to be transformed into a physical form into which the product-related DB performance factors are integrated.
|4.1||SD5.1 - Description of SW Component/ Module/ Database||
Method LOGM is applied to generate a DBMS-oriented data structure. In order to generate a database schema of already available or commercially available database systems the method has to be applied together with DNAV - Data Navigation Modeling and NORM. Together with DNAV and NORM - Normalization, LOGM covers that part in the subproduct SW Design (Database).Schema Definition which 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 views. Furthermore, DBMS-related storage parameters must be defined and all data elements have to be completely defined.
|No.||Interface||Observation||Information in Annex 1|
|5.1||LOGM-ER||The complete E/R model is the starting point for the logical DB modeling. In this connection the (normalized) E/R models are transformed into DBMS-oriented data structures.||4.11 Interface ER-LOGM|
|GDPA Online Last Updated 01.Jan.2002 Updated by Webmaster Last Revised 01.Jan.2002 Revised by Webmaster|