S T R U C T U R A L M O D E L I N G ( M O D E L I N G A S Y S T E M ' S L O G I C A L S T R U C T U R E U S I N G C L A S S E S A N D C L A S S D I A

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1 S T R U C T U R A L M O D E L I N G ( M O D E L I N G A S Y S T E M ' S L O G I C A L S T R U C T U R E U S I N G C L A S S E S A N D C L A S S D I A G R A M S )

2 WHAT IS CLASS DIAGRAM? A class diagram in the Unified Modeling Language (UML) 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. These are main building block in object oriented modeling. They are used both for general conceptual modeling of the systematics of the application, and for detailed modeling translating the models into programming code. In the diagram these classes are represented with boxes which contain three parts

3 ESSENTIAL ELEMENTS OF A UML CLASS DIAGRAM Class Attributes Operations Relationships Associations Aggregation and Composition Generalization Realization Dependency Constraint Rules and Notes

4 CLASS A class with three sections. The upper part holds the name of the class The middle part contains the attributes of the class The bottom part gives the methods or operations the class can take or undertake Describes a set of objects having similar: Attributes (status) Operations (behavior) Relationships with other classes Attributes and operations may have their visibility marked: "+" for public "#" for protected " " for private "~" for package Class Name Attributes Operations Window size: Size visibility: boolean display() hide()

5 STEPS FOLLOWED Draw class symbol in the editor and name it List the class attributes List the class operations/methods Make the links and associations Give notations

9 MULTIPLICITY Declaring an attribute represents a group of objects. Set number: [1..10] Unknown number: [*] {unique}, {notunique}, {ordered}, {readonly} Static attributes Exactly one 1 Zero or more (unlimited) * (0..*) One or more 1..* Zero or one (optional association) Multiplicity Indicators 0..1 Specified range 2..4 Multiple, disjoint ranges 2, 4..6, 8

11 CORE RELATIONSHIPS Associations: An association between two classes indicates that objects at one end of an association recognize objects at the other end and may send messages to them. Example: An Employee works for a Company Employee Company

13 ASSOCIATIONS (CONT.) StaffMember Multiplicity instructor Role name Association name 1..* instructs * Navigable (uni-directional) association Reflexive association Student * Courses pre - requisites 0..3 Role

14 To clarify its meaning, an association may be named. The name is represented as a label placed midway along the association line. Usually a verb or a verb phrase. A role is an end of an association where it connects to a class. May be named to indicate the role played by the class attached to the end of the association path. Usually a noun or noun phrase Mandatory for reflexive associations

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

16 AGGREGATION (CONT.) Aggregation tests: Is the phrase part of used to describe the relationship? A door is part of a car Are some operations on the whole automatically applied to its parts? Move the car, move the door. Are some attribute values propagated from the whole to all or some of its parts? The car is blue, therefore the door is blue. Is there an intrinsic asymmetry to the relationship where one class is subordinate to the other? A door is part of a car. A car is not part of a door.

17 COMPOSITION 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. Circle 1 Point Circle Polygon 3..* Point

19 GENERALIZATION Indicates that objects of the specialized class (subclass) are substitutable for objects of the generalized class (super-class). 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 An abstract class Generalization relationship Shape {abstract} Circle Super Class Sub Class

21 GENERALIZATION A sub-class inherits from its super-class Attributes Operations Relationships A sub-class may Add attributes and operations Add relationships Refine (override) inherited operations A generalization relationship may not be used to model interface implementation.

22 REALIZATION A realization relationship indicates that one class implements a behavior specified by another class (an interface or protocol). An interface can be realized by many classes. A class may realize many interfaces. Linked List <<interface>> List ArrayList

23 CONSTRAINT RULES AND NOTES Constraints and notes annotate among other things associations, attributes, operations and classes. Constraints are semantic restrictions noted as Boolean expressions. UML offers many pre-defined constraints. Customer id: long { value > 0 } 1 { total < $50 } * Order may be canceled Constraint Note

24 CLASS DIAGRAM USES To model the vocabulary of a system. To model the simple collaborations. To model a logical data base schema.

30 SAMPLE CLASS DIAGRAM-ATM( REFERENCE ONLY)

31 LIBRARY MANAGEMENT SYSTEM

32 THANK YOU

PDOM Problem Domain Object Model

PDOM Problem Domain Object Model A R N O N L A Z E R S O N PDOM - PROBLEM DOMAIN OBJECT MODEL 1 Problem Domain Object Model A domain model is a representation of real-world concepts relevant to the domain