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Conceptual Modeling

Conceptual Modeling. Entity-Relationship Diagrams. E-R Model Constructs. Entities Relationships Attributes. E-R Model Notation. Entity. Attribute. One-to-many relationship. Many-to-many relationship. Example of Relationship Type. COMPLETES. EMPLOYEE. COURSE.

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Conceptual Modeling

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  1. Conceptual Modeling Entity-Relationship Diagrams

  2. E-R Model Constructs • Entities • Relationships • Attributes

  3. E-R Model Notation Entity Attribute One-to-many relationship Many-to-many relationship

  4. Example of Relationship Type COMPLETES EMPLOYEE COURSE A particular employee may complete many courses A particular course may be completed by many employees

  5. Cardinality Constraints A cardinality constraint specifies the number of instances that can, or must, participate in a relationship.

  6. Degree of a Relationship Refers to the number of entity types that participate in the relationship. • Unary (degree 1) • Binary (degree 2) • Ternary (degree 3)

  7. Binary Relationships Relationship between the instances of two entity types.

  8. Example of Binary One-to-One Relationship ASSIGNMENT EMPLOYEE PARKING PLACE A particular employee is assigned one parking place A particular parking place may be assigned to only one employee

  9. Example of Binary One-to-Many Relationship MEMBERSHIP DEPARTMENT EMPLOYEE A particular department consists of many employees A particular employee belongs to one department

  10. Example of Binary Many-to-Many Relationship MEMBERSHIP EMPLOYEE COMMITTEE A particular employee may belong to many committees A particular committee consists of many employees

  11. Unary Relationship • A unary relationship, also called a recursive relationship, is a relationship between the instances of a single entity type.

  12. Example of Unary One-to-One Relationship MARRIAGE PERSON A particular person may be married to only one other person

  13. Example of Unary One-to_Many Relationship SUPERVISORY EMPLOYEE A particular employee may supervise many employees A particular employee has only one supervisor

  14. Example of Unary Many-to_Many Relationship BILL_OF_MATERIAL PART A particular part may consist of many component parts A particular part may be the component for many parts

  15. Ternary Relationship A ternary relationship is a simultaneous relationship among the instances of three entity types.

  16. Example of Ternary Many-Many-Many Relationship SKILL EMPLOYEE PROJECT SKILL ASSIGNMENT A particular employee may use a particular skill on many projects In a particular project, a particular skill may be used by many employees A particular employee working on a particular project may use many skills

  17. Another Example of Ternary Many-Many-Many Relationship PART VENDOR WAREHOUSE SUPPLIES A particular part , supplied by a particular vendor, may be stored in many warehouses A particular part, stored in a particular warehouse, may be supplied by many vendors In a particular warehouse, a particular vendor may supply many parts

  18. Example of Ternary Many-Many-One Relationship SEMESTER INSTRUCTOR COURSE TEACHES In a particular semester, a particular instructor may teach many courses A particular instructor may teach a particular course in many semesters In a particular semester, a particular course is taught by only one instructor

  19. Comparing Notation BELONGS_TO EMPLOYEE DEPARTMENT Belongs To EMPLOYEE DEPARTMENT Belongs_to EMPLOYEE DEPARTMENT Consists_of

  20. Example of Composite Attribute

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