1. Domain Models Part 1

2. What are you going to learn about today?
Domain modeling:
why?
what?
how?
Diagramming domain models

3. Iterative Development Process
We are here
Planning
Requirements
Analysis
Design
Implementation
Deployment
Testing
Evaluation
Initial Planning

4. Analysis bridges the gap between requirements and design
Analysis
Requirements

5. Domain Model
“Most important—and classic—model in OO analysis” –Larman, p131
Captures entities, attributes, and relationships in the problem domain
Represented with UML class diagram
Conceptual classes
As opposed to software or implementation classes
Acts as inspiration for some software classes
Lowers representational gap

6. POS Domain Model
Classes: concepts or entities in the problem domain (not software)

7. 3 aspects of conceptual classes
1. Symbol—words or images representing a conceptual class
"A sale represents the event of a purchase transaction. It has a date and time."
2. Intention—definition of a conceptual class (put in glossary!)
3. Extension—set of examples to which conceptual class applies

8. POS Domain Model
Attributes: number or text properties of conceptual classes
Classes: concepts or entities in the problem domain (not software)

9. Is it a class or an attribute?
If we do not think of an idea/thing as a number or text in the real world, it is probably a conceptual class, not an attribute

10. POS Domain Model
Associations: relationships between classes
Classes: concepts or entities in the problem domain (not software)
Attributes: number or text properties of conceptual classes

11. Associations Reading direction Multiplicities: Read as
each Register records 0 or more Sales
each Sale is recorded by exactly 1 Register
Name

12. Examples of multiplicities8
Also common to see 0..*

13. POS Domain Model How many Stores can an Item be stocked in?
How many Items can a Store stock?
How many Registers does a Store house?
How many Sales LineItems per Sale?
How many Sales LineItems can a particular Item be recorded in?

14. How to find conceptual classes: Noun phrase identification
Identify nouns and noun phrases in descriptions of a domain
Nouns = candidate classes or attributes
Example:

15. Tip: Think like a mapmaker
Use existing names in the territory
Exclude irrelevant or out-of-scope features
Do not add things that are not there

16. Tip: Sketch classes starting from the upper left
Sale
Payment
Store
address

17. Think-Pair-Share Activity: Creating a Domain Model
Think-Pair-Share Activity: Creating a Domain Model
Think
Identify nouns and noun phrases—for inspiration
Sketch class diagram
Group
Join your partner at the whiteboard
Collaboratively draw a class diagram
Make tentative decisions quickly, then debate
Share
I’ll randomly select diagram(s) to discuss
Identify one thing that you wish you’d thought of
Identify one thing that you would do differently

18. Summary Domain models Conceptual class diagrams Tips: Attributes
Summary
Domain models
Conceptual class diagrams
Attributes
Associations
Multiplicities
Tips:
Identify noun phrases
Think like mapmaker
Draw from upper left