OO Domain Modeling With UML Class Diagrams and CRC Cards

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

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 Software Engineering OO Domain Modeling

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) Software Engineering OO Domain Modeling

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. Software Engineering OO Domain Modeling

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 Software Engineering OO Domain Modeling

What is a Domain Model? Objectives
identify concepts related to current development cycle requirements create initial conceptual model Identify attributed add specification concepts Software Engineering OO Domain Modeling

What is a Domain Model? Software Engineering OO Domain Modeling

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. Software Engineering OO Domain Modeling

From Use Cases to: Objects, Attributes, Operations (methods) -“evolutionary ”
Software Engineering OO Domain Modeling

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 Software Engineering OO Domain Modeling

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 Software Engineering OO Domain Modeling

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 Software Engineering OO Domain Modeling

Find conceptual classes

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 Software Engineering OO Domain Modeling

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 Software Engineering OO Domain Modeling

Identifying objects Software Engineering OO Domain Modeling

Identifying Operations ‘methods’

Objects Software Engineering OO Domain Modeling

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 Software Engineering OO Domain Modeling

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 Software Engineering OO Domain Modeling

Example: a typical description

Mapping parts of speech to object model components

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. Software Engineering OO Domain Modeling

Example: Initial POS domain model
SalesLineItem Register Item Store Sale Payment Software Engineering OO Domain Modeling

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. Software Engineering OO Domain Modeling

Example: Initial POS domain model

Example: Initial Domain model of the Monopoly Game

Example: Domain model of the Monopoly Game

Agile modeling style Software Engineering OO Domain Modeling

Class or Attributes Software Engineering OO Domain Modeling

Description Class Software Engineering OO Domain Modeling

Associations Software Engineering OO Domain Modeling

Association, aggregation and composition

Association between classes Who does What

When to show association

Associations and implementation

Association Notation Software Engineering OO Domain Modeling

Naming association Software Engineering OO Domain Modeling

Applying UML: multiplicity

Multiplicity values Software Engineering OO Domain Modeling

Applying UML: multiplicity

Multiple association between two classes

Find association Software Engineering OO Domain Modeling

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 Software Engineering OO Domain Modeling

Example: POS Domain Model

Example: Monopoly Game Partial Domain Model

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. Software Engineering OO Domain Modeling

Attributes: UML Notation

Suitable attribute types

Data types as attributes

Attributes are NOT foreign keys

Generalization Software Engineering OO Domain Modeling

OO Domain Modeling With UML Class Diagrams and CRC Cards

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