|4.11 Interface ER-LOGM|
In this case, the complete E/R model from SD3.4 - Definition of Requirements for the Quality of the SW/HS Unit is transformed by the LOGM basic method into a DBMS-oriented data structure.
DBMS-oriented data structures can be hierarchical, network-oriented or relational data structures without the special characteristics of physical storage parameters of commercial database systems, though. The required rules for the above mentioned transformation have also been described in /Batini, 92/ p. 309-404 and in /Atre, 80/ chap. 6./Atre, 80/ p. 163-174.
|Step 1||Elimination of unnecessary transitive relation types between entity types in the E/R model.|
Therefore, the relation type in Figure 4.14 from A to C is unnecessary if it does not cause semantic information to be lost.
|Step 2||Deviation of all hierarchical relation types from the E/R model|
(/Atre, 80/, p. 165).
|Step 3||Dissolution of multiple hierarchical dependences in the E/R model.|
Situations as shown in Figure 4.15 must be dissolved during the transformation into hierarchical data structures. Depending on the type of the hierarchical "parents", several possibilities exist (compare /Atre, 1980/, p. 167-172).
|/Atre, 1980/||Contains a comprehensive description of the rules for the logical data modeling in chapter 6 (Logical Model)|
|/Batini, 1992/||Contains the most complete description of the logical data modeling that can be found in the literature at present in section 3 (chap.11, 12, 13, 14).|
|GDPA Online Last Updated 01.Jan.2002 Updated by Webmaster Last Revised 01.Jan.2002 Revised by Webmaster|