Lecture 3 CMPS 328 Generalization Rules Using Classes Diagramming and Definitions Attributes Rules Overlaps Benefits Stopping Relationships 1 / 22 Subt ypes and Supert ypes CMPS 328 – Advanced Databases www.gheadley.org/ub/cmps328 University of Belize February 10, 2006 Lecture 3 CMPS 328 Generalization Rules Using Classes Diagramming and Definitions Attributes Rules Overlaps Benefits Stopping Relationships 2 / 22 Outline 1 Different Levels of Generalization 2 Rules versus Stability 3 Using Subtypes and Supertypes 4 Subtypes and Supertypes as Entity Classes 5 Diagramming and Definitions 6 Attributes of Supertypes and Subtypes 7 Nonoverlapping and Exhaustive 8 Overlapping Subtypes and Roles 9 Benefits of Subtypes Lecture 3 CMPS 328 Generalization Rules Using Classes Diagramming and Definitions Attributes Rules Overlaps Benefits Stopping Relationships 3 / 22 Different Levels of Generalization Designing a database for family trees Data for mothers, fathers, marriages and children Simple problem statement that is quite hard Family tree designs Lecture 3 CMPS 328 Generalization Rules Using Classes Diagramming and Definitions Attributes Rules Overlaps Benefits Stopping Relationships 4 / 22 Different Levels of Generalization Marriage class resolves many-to-many “be married to” Note optionality of “mother of” and “father of” While all have mothers, will run out of knowledge Choice of classes is the issue Nouns from problem, mother, father, child overlap Child, Mother have redundant data Examples take two approaches Person concept and man, woman concept
This document is posted to help you gain knowledge. Please leave a comment to let me know what you think about it! Share it to your friends and learn new things together.