Databases The Enhanced Entity–Relationship (EER) Model 4.1. What is a subclass? When is a subclass needed in data modeling? 4.2. Define the following terms: superclass of a subclass, superclass/subclass rela- tionship, IS-A relationship, specialization, generalization, category, specific (local) attributes, and specific relationships. 4.3. Discuss the mechanism of attribute/relationship inheritance. Why is it use- ful? 4.4. Discuss user-defined and predicate-defined subclasses, and identify the dif- ferences between the two. 4.5. Discuss user-defined and attribute-defined specializations, and identify the differences between the two. 4.6. Discuss the two main types of constraints on specializations and generalizations. 4.7. What is the difference between a specialization hierarchy and a specializa- tion lattice? 4.8. What is the difference between specialization and generalization? Why do we not display this difference in schema diagrams? 4.9. How does a category differ from a regular shared subclass? What is a cate- gory used for? Illustrate your answer with examples. 4.10. For each of the following UML terms (see Sections 3.8 and 4.6), discuss the corresponding term in the EER model, if any: object, class, association, aggre- gation, generalization, multiplicity, attributes, discriminator, link, link attri- bute, reflexive association, and qualified association. 4.11. Discuss the main differences between the notation for EER schema dia- grams and UML class diagrams by comparing how common concepts are represented in each. 4.12. List the various data abstraction concepts and the corresponding modeling concepts in the EER model. 4.13. What aggregation feature is missing from the EER model? How can the EER model be further enhanced to support it? 4.14. What are the main similarities and differences between conceptual database modeling techniques and knowledge representation techniques? 4.15. Discuss the similarities and differences between an ontology and a database schema
The Enhanced Entity–Relationship (EER) Model 4.1. What is a subclass? When is a subclass needed in data modeling? 4.2. Define the following terms: superclass of a subclass, superclass/subclass rela- tionship, IS-A relationship, specialization, generalization, category, specific (local) attributes, and specific relationships. 4.3. Discuss the mechanism of attribute/relationship inheritance. Why is it use- ful? 4.4. Discuss […]