Database Design With Semantic Object Models Transformation of Semantic Objects into Relational Database Designs Sample Objects

Seven Types of Semantic Objects Simple Objects Single relation. Fig. 7-2,1 Composite Objects One relation for the object and another relation for each multivalued attribute. The key of these relations is the composite of the identifier of the object plus the identifier of the group. Fig. 7-3,4 Compound Objects The relationships (1:1, 1:N, N:M) between objects need to be considered.

Semantic Objects Into Relations (Cont.) 1:1 Compound Objects One relation is needed for each object. Relations are associated by placing the key of either relation as a foreign key in the other relation. Fig. 7-6,7 1:N and N:1 Compound Objects Each object is represented with a relation and the key of the parent is place in the child. Fig. 7-8,9 N:M Compound Objects One relation is needed for each object and a third one to be the intersection relation. Fig. 7-10,11

Semantic Objects Into Relations (Cont.) Hybrid Objects Transformed into relations using a combination of the techniques for composite and compound objects. Fig.7-12,13,14 Association Objects Use a relation for each of the three associated objects, and then represent the relationships among the objects using the strategies used with compound objects. Fig. 7-15,16

Semantic Objects Into Relations (Cont.) Supertype (Parent) /Subtype Objects Define a relation for the parent object and one for each of the subtype objects. The key of all these relations in the key of the parent. Fig. 7-17,18 Archetype/Version Objects These are compound objects that model various instances of the basic object e.g. releases of software products. Fig. 7-19,20

Sample Objects Subscription Form -> Fig. 7-21 Product Description -> Fig. 7-22 Traffic-Warning Citation -> Fig. 7-23