1. Bordoloi CMIS 450 Database Design Dr. Bijoy Bordoloi Enhanced E-R Modeling (EER)

2. Bordoloi Sub-entities A sub-entity is a subset of another entity, called the super-entityA sub-entity is a subset of another entity, called the super-entity The sub-entity is always existence- dependent on the super entityThe sub-entity is always existence- dependent on the super entity COMPUTER MAINFRAME EMPLOYEE PROGRAMMER

3. Bordoloi Sub-entities EMPPLOYEE AGENT CLERK SALARIED HOURLY PROGRAMMER SYSTEMS APPLICATIONS

4. Bordoloi Sub-entity classes A class is a group of mutually exclusive sub- entitiesA class is a group of mutually exclusive sub- entities Sub-entities of class are vertically aligned in diagramSub-entities of class are vertically aligned in diagram One super-entity may have several unrelated classesOne super-entity may have several unrelated classes

5. Bordoloi Sub-entity classes EMPLOYEE AGENT CLERK SALARIED HOURLY PROGRAMMER SYSTEMS APPLICATIONS PROG-CLASS WAGE-CLASSJOB-CODE

6. Bordoloi Sub-entity classes Each class corresponds to an (optional) class attribute of the super-entityEach class corresponds to an (optional) class attribute of the super-entity

7. Bordoloi Attribute Inheritance The attributes of a super-entity apply to all of its sub-entitiesThe attributes of a super-entity apply to all of its sub-entities The converse is false, in generalThe converse is false, in general

8. Bordoloi Attribute Inheritance EMPLOYEE AGENT CLERK SALARIED HOURLY PROGRAMMER SYSTEMS APPLICATIONS COMMISION TERRITORY TYPING SPEED MACHINE LANGUAGELEVEL SS-NUM NAMESEX EXTENSION OVER-TIME RATE

9. Bordoloi There is always an implicit IS-A relationship between a sub-entity and its super-entityThere is always an implicit IS-A relationship between a sub-entity and its super-entity Cardinality of IS-A is always maximum 1-1 and minimum 1-0 (super-entity — sub-entity)Cardinality of IS-A is always maximum 1-1 and minimum 1-0 (super-entity — sub-entity) Super-entity — Sub-entity Cardinality EMPLOYEE PROGRAMMER IS-A

10. Bordoloi Super-entity — Sub-entity Cardinality IS-A relationship is normally omitted from diagram for clarityIS-A relationship is normally omitted from diagram for clarity E1E1 E2E2 E3E3 E4E4 P1P1 P2P2 P3P3 E5E5............

11. Bordoloi Example Example SUPPLIER PROJECT DEPARTMENT WAREHOUSEPART TASK STAFF SUPERVISOR EMPLOYEE SUPPLY WORK-IN ASSIGN-TOSTORE MANAGE BELONGS-TO EXECUTE

12. Bordoloi Example of Dictionary Entity: EMPLOYEEEntity: EMPLOYEE All employees of XYZ Corp, including board members, part-time employees and retirees, but excluding contractors. All employees of XYZ Corp, including board members, part-time employees and retirees, but excluding contractors. Attribute: EMP-NUMAttribute: EMP-NUM Use: identifies employee Use: identifies employee Employee identification number, assigned by Personnel department at hire-in. Employee identification number, assigned by Personnel department at hire-in.

13. Bordoloi Example of Dictionary Attribute: (FNAME, MNAME, LNAME, SUFFIX)Attribute: (FNAME, MNAME, LNAME, SUFFIX) Use: describes EMPLOYEE Use: describes EMPLOYEE Full legal name of employee. For Asian employees, LNAME is family name…and so on… Full legal name of employee. For Asian employees, LNAME is family name…and so on… Entity: DEPARTMENTEntity: DEPARTMENT All organizational units at the departmental and group level. Does not include divisions or sections… and so on… All organizational units at the departmental and group level. Does not include divisions or sections… and so on…

14. Bordoloi Example of Dictionary Example of Dictionary Relationship:WORK-INRelationship:WORK-IN Related Entities:EMPLOYEERelated Entities:EMPLOYEE DEPARTMENT DEPARTMENT Cardinality:1-N maximumCardinality:1-N maximum 0-1 minimum 0-1 minimum Describes administrative assignment of personnel for supervision and performance review. Does not include project assignmentsDescribes administrative assignment of personnel for supervision and performance review. Does not include project assignments

15. Bordoloi Relationship:MANAGERelationship:MANAGE Related Entities:SUPERVISORRelated Entities:SUPERVISOR PROJECT PROJECT Cardinality:1-N maximumCardinality:1-N maximum 1-1 minimum 1-1 minimum Front-line project management responsibility. Unrelated to departmental management assignments, which are documented in relationship DIRECT…and so on…. Example of Dictionary Example of Dictionary