Chapter 4

1. Chapter 4 Systems Analysis and Design in a Changing World, 6th Edition

2. Domain Classes Chapter 4 Systems Analysis and Design in a Changing World 6th Ed Satzinger, Jackson & Burd

3. Chapter 4 Outline • “Things” in the Problem Domain • Data entities • Domain classes • The Domain Model Class Diagram • The Entity-Relationship Diagram Systems Analysis and Design in a Changing World, 6th Edition

4. Overview • Chapter 3 • Functional Requirements • Events • Cases • Chapter 4 • Data entities / Classes • Attributes Systems Analysis and Design in a Changing World, 6th Edition

5. “Things” in the Problem Domain • Problem domain • The specific area (or domain) of the users’ business • Scope of the system • What “things” does the business need to track info? • Examples of “Things” • products, sales, shippers, customers, invoices, payments, etc. • Called “classes” (UML) or “entities” • “Things” eventually modelled • If you don’t care about the “thing”, don’t model it! Systems Analysis and Design in a Changing World, 6th Edition

6. Types of Things • Are there any tangible things? Are there any organizational units? Sites/locations? Are there incidents or events that need to be recorded? Systems Analysis and Design in a Changing World, 6th Edition

7. Details about Entities/Classes • Attribute • describes one piece of information about each instance of the class • Customer has first name, last name, phone number • Identifier or key • One attribute uniquely identifies an instance of the class. Required for data entities, optional for domain classes. Customer ID identifies a customer • Compound attribute • Two or more attributes combined into one structure to simplify the model. (E.g., address rather than including number, street, city, state, zip separately). Sometimes an identifier or key is a compound attribute. Systems Analysis and Design in a Changing World, 6th Edition

8. Attributes and Values • Class is a type of thing. Object is a specific instance of the class. Each instance has its own values for an attribute Systems Analysis and Design in a Changing World, 6th Edition

9. Associations Among Things • Association— a naturally occurring relationship between classes (UML term) Systems Analysis and Design in a Changing World, 6th Edition

10. Just to Clarify… • Called association on class diagram in UML • Multiplicity is term for the number of associations between classes: 1 to 1 or 1 to many • We are emphasizing UML in this text • Called relationship on ERD in database class • Cardinality is term for number of relationships in entity relationship diagrams: 1 to 1 or 1 to many • Associations and Relationships apply in two directions • Read them separately each way • A customer places an order • An order is placed by a customer Systems Analysis and Design in a Changing World, 6th Edition

11. Minimum and Maximum Multiplicity • Associations have minimum and maximum constraints • Minimum: Zero or one • Maximum: one or many Systems Analysis and Design in a Changing World, 6th Edition

12. Types of Associations • Binary Association • Unary Association (recursive) • Ternary Association (three) Systems Analysis and Design in a Changing World, 6th Edition

13. A Simple Domain Model Class Diagram • Note: This diagram matches the semantic net shown previously • A customer places zero or more orders • An order is placed by exactly one customer • An order consists of one or more order items • An order item is part of exactly one order Systems Analysis and Design in a Changing World, 6th Edition

14. UML Notation for Multiplicity Systems Analysis and Design in a Changing World, 6th Edition

15. Domain Model Class Diagramfor course enrollment at a university • Where is each student’s grade remembered in this model? • Each section has many grades and each grade is association with a student • Each student has many grades and each grade is association with a section Systems Analysis and Design in a Changing World, 6th Edition

16. Refined Course Enrollment Modelwith an Association Class CourseEnrollment • Association class— an association that is treated as a class in a many to many association because it has attributes that need to be remembered, such as grade Systems Analysis and Design in a Changing World, 6th Edition

17. Generalization/SpecializationInheritance for RMO Three Types of Sales • Abstract class— a class that allow subclasses to inherit characteristics but never gets instantiated. In Italics (Sale above) • Concrete class— a class that can have instances Systems Analysis and Design in a Changing World, 6th Edition

18. Whole Part RelationshipsComputer and its Parts • Note: this is composition, with diamond symbol. • Whole part can have multiplicity symbols, too (not shown) Systems Analysis and Design in a Changing World, 6th Edition

19. RMO CSMS ProjectComplete Domain Model Class Diagram Systems Analysis and Design in a Changing World, 6th Edition

20. Example of ERD Notation • A simple ERD without showing attributes Systems Analysis and Design in a Changing World, 6th Edition

21. ERD Cardinality Symbolsoften called the crows feet notation Systems Analysis and Design in a Changing World, 6th Edition

22. Expanded ERD with Attributes • Note: This diagram matches the semantic net shown previously • Also matches a domain model class diagram shown previously Systems Analysis and Design in a Changing World, 6th Edition

23. At the end of the day… • Determine entities (things in the domain) • Attributes (of entities) • Keys (Primary, Foreign) • Data types (integer, string, etc) • Relationships (which entities are related) • Cardinality (how are entities related) Systems Analysis and Design in a Changing World, 6th Edition

24. Running Case Studies SBRU – Domain Class Model (example 4.14). Just brainstorm OTSC – Domain Class Model (example 4.14). Just brainstorm SMD – Draw out the diagram, walk us through the changes. Systems Analysis and Design in a Changing World, 6th Edition