Business Requirements (PDF)

• Business domain language
• Narratives
• Rules (bullet points)
• Highlighted nouns/verbs

Example

• Rules:
  • Multiple students in the class
  • Each student has multiple grades
  • Some grades assigned, some not
  • A grade range 0-100
  • Only care about current class
• Nouns: Class, Student, Grade
• Verbs: Has, assigned
• Attributes: class, student

Conceptual Model (UML)

• Class diagram from UML
  • Used for conceptual model
• Attributes can have multiple values
• In class diagrams, methods don't matter, foreign keys don't matter
  • Have attributes and attribute types (business specific)
• Cardinality:
  • 1: 1 relation
  • 1..*: Between 1 and any number of relations
  • *: Any number of relations
  • 1: May or may not have 1 relation
• Name your relations, include direction and cardinality
  • Given "Team" and "Player" tables:
  • Team <- plays, 0..* Player
• Can have aggregations, compositions, generalizations
• Generalization:
  • Inherit from parent and add attributes
  • One parent class can have multiple subclasses
    • subclass should have a new attribute
• Composition:
  • Two entities
  • Remove one, other doesn't exist
  • Post, Comments
    • Remove post -> comments don't exist
• Aggregation:
  • Two entities, one of them is a sub
  • If we remove the parent, the sub still exists
  • e.g., we have photo albums which hold photos. if we delete the albums, the photos will still exist.

Logical Model

• Relational: ERD (crow's foot)
• Start from conceptual model
• Choose database type
  • Solve multiple value attributes
  • Solve many-to-many relationships
  • Identify foreign keys
• Can't have generalizations, compositions, aggregations

Physical Level

• Relational: SQL DDL
• Have the relation schema
• Make the actual code

GENERAL PROCEDURES