Class diagram Description IS351-System Analysis Class diagram Description

Class Diagram Components Classes Attribute Operations Associations Aggregation Composition Generalization Multiplicity A class diagram is a type of static structure diagram that describes the structure of a system by showing the system's classes, their attributes, operations (or methods), and the relationships among objects.

The Domain Model Class Diagram A class diagram that only includes classes from the problem domain. Design class diagram vs domain model class diagram !!

Classes Window Class Name size: Size visibility: boolean Attributes display() hide() Class Name Attributes Operations A class is the description of a set of objects having similar attributes, operations, relationships and behavior.

Associations Example: “An Employee works for a Company” To clarify its meaning, an association may be named. Usually a verb or a verb phrase. Company Department Employee Associations denote relationships between classes

Multiplicity indicates that (at least) one of the two related classes makes reference to the other 0..1 No instances, or one instance (optional, may) 1 Exactly one instance 0..* or * Zero or more instances 1..* One or more instances (at least one) Student Course Doctor 0..* 0..6 1..* 1..2 Registered in Teaches

Aggregation Models a “is a part-part of” relationship. Whole Part Door Car Door House 1..* 2..* A special form of association that models a whole-part relationship between an aggregate (the whole) and its parts.

Composition A strong form of aggregation Pages Person Eye 0..* 2 Book A strong form of aggregation The whole is the sole owner of its part. The part object may belong to only one whole Multiplicity on the whole side must be zero or one. The life time of the part is dependent upon the whole. The composite must manage the creation and destruction of its parts.

Generalization (inheritance)  indicates that one of the two related classes (the subclass) is considered to be a specialized form of the other (the super type) and superclass is considered as 'Generalization' of subclass “is kind of” relationship. {abstract} is a tagged value that indicates that the class is abstract. The name of an abstract class should be italicized Shape {abstract} Circle Super Class Sub Class An abstract class Generalization relationship

How to model class diagram Find new classes. Review name, attribute and methods for each class. Find associations between classes. Label the generic associations. Determine the multiplicity of the associations. Review associations.

Example of identifying Class Relations, Multiplicities, Attributes

The Noun Technique A technique to identify problem domain objects by finding and classifying the nouns in a dialog or description. a noun is a person, place, or thing. The analyst lists all nouns without thinking too much about them and without talking much to users.

The Noun Technique list all the nouns that users mention when talking about the system add to the list any additional nouns about the problem domain of the system. Refine the noun list. Ask these questions about each noun: Is it a unique thing the system needs to know about? Is it inside the scope of the system I am working on? Does the system need to remember more than one of these items?

Multi-Clinic System Case Study In a multi-clinic system a patient makes a call for an appointment reservation. Once the call is done, the system has to record all patient information such as patient name, address, and telephone number. In a multi-clinic system a patient makes a call for an appointment reservation. Once the call is done, the system has to record all patient information such as patient name, address, and telephone number. During the notification with a patient, he/she should know all possible appointments in order to choose his/her desired appointment. During the notification with a patient, he/she should know all possible appointments in order to choose his/her desired appointment. The patient may cancel or change his/her appointment before 24 hours from his actual appointment. The patient may cancel or change his/her appointment before 24 hours from his actual appointment. Two daily reports have to be prepared to each doctor, one of them is about patient report and the other is an appointment report. Two daily reports have to be prepared to each doctor, one of them is about patient report and the other is an appointment report.

Multi-Clinic System Case Study When a patient comes for examination, the doctor writes a prescription which includes all drugs the patient have to take, number of times and dose he has to take for each medicine. In the end, the doctor Prints the prescription to the patient before he leaves. When a patient comes for examination, the doctor writes a prescription which includes all drugs the patient have to take, number of times and dose he has to take for each medicine. In the end, the doctor Prints the prescription to the patient before he leaves.

MCS Class Diagram