1. OO Domain Modeling With UML Class Diagrams and CRC Cards
Chapter 6
Princess Nourah bint Abdulrahman University
College of Computer and Information Sciences Department of Computer Science
Dr. Doaa Sami Khafaga

2. Objectives
The main objective of this chapter is to know: how to properly use the most essential features of UML class diagrams, and the typical problems you will encounter when modeling with class diagrams.
In this chapter we:
Introduce the evolutionary approach for building classes
Explain how to identify objects and attributes of classes
Describe the technique of CRC ‘Class Responsibility and Collaborator’
Explain how classes are related in a class diagram
Explain generalization, association, aggregation and composition
Introduce object diagrams
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OO Domain Modeling

3. What is a Domain Model?
Use cases looked at the system’s environment (actors) and the system’s external behavior.
Use cases consider the system as a black box and help us understand how the system as a whole interacts with the outside word.
Now we turn to consider the inside of the system. We do this by building the domain model, which shows what the black box (the system) encloses.
uses cases elaborate the system’s behavioral characteristics (sequence of stimulus-response steps),
domain model gives details of the systems structural characteristics (system parts and their arrangement)
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4. What is a Domain Model?
uses cases elaborate the system’s behavioral characteristics (sequence of stimulus-response steps),
domain model gives details of the systems structural characteristics (system parts and their arrangement)
The next step is to model the inside of the system. We do this by building the domain model, which shows what the black box (the system) encloses.
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5. What is a Domain Model?
Illustrates meaningful concepts in the problem domain.
Usually expressed in the form of static diagrams (in Rational this implies a high-level class diagram).
Is a representation of real-world things; not software components (of the system under development).
No operations are defined or specified in the conceptual model.
Should show concepts, associations between concepts, and attributes of concepts.
Serves as a source of software objects.
S.H
2009
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6. What is a Domain Model? Objectives
identify concepts related to current development cycle requirements
create initial conceptual model
Identify attributed
add specification concepts
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7. What is a Domain Model?
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8. What constitutes a good model?
A model should
use a standard notation
be understandable by clients and users
lead software engineers to have insights about the system
provide abstraction.
Models are used:
to help create designs
to permit analysis and review of those designs
as the core documentation describing the system.
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9. From Use Cases to: Objects, Attributes, Operations (methods) -“evolutionary ”
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10. Building the Domain Model
A useful strategy for building a domain model is to start with:
the “boundary” concepts that interact directly with the actors
and then identify the internal concepts
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11. Domain Model Relationships
Conceptual Class Diagram
Classes, attributes, associations
Domain objects
Use Case Model
Functional Requirements
Domain Model
Define terms
Glossary
Interaction Diagrams
Dynamic Behavior
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12. Steps to create a Domain Model
Identify Candidate Conceptual classes
Draw them in a Domain Model
Add associations necessary to record the relationships that must be retained
Add attributes necessary for information to be preserved
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13. Find conceptual classes
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14. Use a category list Finding concepts using the concept category list :
Physical objects: register, airplane, blood pressure monitor
Places: airport, hospital
Catalogs: Product Catalog
Transactions: Sale, Payment, reservation
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15. Identify conceptual classes from noun phrases
Finding concepts using Noun Phrase identification in the textual description of the domain .
Noun phrases may also be attributes or parameters rather than classes:
If it stores state information or it has multiple behaviors, then it’s a class
If it’s just a number or a string, then it’s probably an attribute
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16. Identifying objects
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17. Identifying Operations ‘methods’
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18. Objects
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19. Example: Identify conceptual classes from noun phrases
Consider the following problem description, analyzed for Subjects, Verbs, Objects:
The ATM verifies whether the customer's card number and PIN are correct.
SC V R O O A O A
If it is, then the customer can check the account balance, deposit cash, and withdraw cash.
S R V O A V O A V O A
Checking the balance simply displays the account balance.
S M O A V O A
Depositing asks the customer to enter the amount, then updates the account balance.
M S V O R V OA V OA
Withdraw cash asks the customer for the amount to withdraw; if the account has enough cash,
S M A O V O R OA V S C V O A
the account balance is updated. The ATM prints the customer’s account balance on a receipt.
O A V C S V O A O
Analyze each subject and object as follows:
Does it represent a person performing an action? Then it’s an actor, ‘R’.
Is it also a verb (such as ‘deposit’)? Then it may be a method, ‘M’.
Is it a simple value, such as ‘color’ (string) or ‘money’ (number)? Then it is probably an attribute, ‘A’.
Which NPs are unmarked? Make it ‘C’ for class. Verbs can also be classes, for example:
Deposit is a class if it retains state information
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20. Mapping parts of speech to object model components [Abbott, 1983]
Part of Speech
Model Component
Examples
Proper noun
Instance
Ali
Common noun
Class
Student, Customer,..
Doing verb
Operation
Buy, check,..
Being verb
Inheritance
Is a kind of, is one of either
Having verb
Aggregation (Composition)
Has, consists of, includes
Modal verb
Constraints
Must be
Adjective attributes
Attributes
3 years old
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21. Example: a typical description
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22. Mapping parts of speech to object model components
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23. Identify conceptual classes from noun phrases: POS
Examine use case descriptions.
Example: Process Sale use case:
Main success scenario:
Customer arrives at a POS checkout counter.
Cashier starts a new sale.
Cashier enters an item ID.
System records sale line item. It then presents a description of the item, its price, and a running total.
● ….
Possible source of confusion: Is it an attribute or a concept?
If X is not a number or a text then it probably is a conceptual class.
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24. Example: Initial POS domain model
SalesLineItem
Register
Item
Store
Sale
Payment
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25. Class and Class diagram
Class naming: Use singular names
because each class represents a generalized version of a singular object.
Class diagrams are at the core of OO Engineering.
Things naturally fall into categories (computers, automobiles, trees...).
We refer to these categories as classes.
An object class is an abstraction over a set of objects with common:
attributes (states)
and the services (operations) (methods) provided by each object
Class diagrams provide the representations used by the developers.
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26. Example: Initial POS domain model
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27. Example: Initial Domain model of the Monopoly Game
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28. Example: Domain model of the Monopoly Game
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29. Agile modeling style
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30. Software Engineering
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31. Software Engineering
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32. Software Engineering
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33. Software Engineering
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34. Software Engineering
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35. Software Engineering
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36. Software Engineering
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37. Software Engineering
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38. Class or Attributes
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39. Class or Attributes
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40. Description Class
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41. Associations
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42. Associations
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43. Association, aggregation and composition
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44. Association between classes Who does What
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45. When to show association
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46. Associations and implementation
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47. Association Notation
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48. Association Notation
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49. Naming association
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50. Applying UML: multiplicity
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51. Multiplicity values
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52. Applying UML: multiplicity
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53. Applying UML: multiplicity
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54. Multiple association between two classes
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55. Find association
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56. Find association High priority associations
A is a physical or logical part of B
A is physically or logically contained in/on B
A is recorded in B
Other associations
A uses or manages or controls B (Pilot -airplane)
A owns B (Airline -airplane)
Each of the two ends of an association is called a role. Roles have
name
multiplicity expression
navigability
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57. Example: POS Domain Model
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58. Example: Monopoly Game Partial Domain Model
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59. Attributes Attribute - is a logical data value of an object
Include the following attributes in a conceptual model
those for which the requirements suggest or imply a need to remember information
For example:
Sale needs a dateTime attribute
Store needs a name and address.
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60. Attributes: UML Notation
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61. Suitable attribute types
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62. Data types as attributes
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63. Attributes are NOT foreign keys
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64. Generalization
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65. Aggregation models a whole-part relationship between an14
Association is used when both of the involved classes are equaly important.
 Aggregation is a special form of association that
models a whole-part relationship between an
aggregate (the whole) and its parts.
 Aggregation shows how classes that are collections are composed of other classes.
 Aggregation is a part-of relationship.
Car Wheel

66. Composition 15  Composition is a strong form of aggregation.
 Aggregation is used to model a whole-part relationship between an aggregate (whole) and its parts.
 Composition is a strong form of aggregation.
 The whole is the only owner of its part.
 Multiplicity on the whole side must be one.
 The lifetime of the part is dependent upon the whole.
 When Circle is destroyed, Point is also destroyed.
 The composite must manage the creation and destruction of its parts.

67. Composition (C++ Implementation)16
Restaurant Menu
class Restaurant{ class Menu{ };
Menu m; };
....