Prepared By:Mitali sonar

Transcription

1 Prepared By:Mitali sonar

2 OOAD It focuses on objects where system is broken down in terms of the objects that exist within it. Functions (behaviour) and data (state) relating to a single object are selfcontained or encapsulated in one place. 2

3 OBJECTS Object is an abstraction of something in a problem domain, reflecting the capabilities of the system to keep information about it, interact with it, or both. Objects are entities in a software system which represent instances of real-world and system entities Concept, abstraction or thing with identity It knows things (has attributes) It does things (provides services or has methods) 3

4 OBJECTS Object Identity Behaviors State An employee Mr. John Join(), Retire() Joined, Retired. A book Book with title Object Oriented Analysis Design A sale Sale no 0015, 15/12/98 AddExemplar, SendInvoiced(), Cancel(). Rent, available, reserved Invoiced, cancelled. 4

5 CLASS Class is a description of a set of objects that share the same attributes, operations, methods, relationship and semantics. Object classes are templates for objects. They may be used to create objects. An object represents a particular instance of a class. EX - class car, defines the property color. Each individual car object i.e. alto or zen or i10 will have a value for this property, such as "maroon," silver" or "white." 5

6 TERM OF OBJECTS Attribute: data items that define object. Operation: function in a class that combine to form behavior of class. Methods: the actual implementation of procedure (the body of code that is executed in response to a request from other objects in the system). 6

7 CLASS DIAGRAM CLASS DIAGRAM Graphic notation for modeling classes & relationship. Use to represent structure of applications. OBJECT DIAGRAM Shows individual objects, relationship & helpful for documenting test cases & discussing for example. Person Smith : Person Atul : Person class objects 7

8 Class Diagram-VALUES & ATTRIBUTES Value is piece of data Attribute is a named property of class that describe a value held by each object of class. Object is to a class as as value is to attributes name Person birthdate name= Joe Joe:Person birthdate=21 oct 1983 Class with attribute Object with values 8

9 Modeling Notation Person name : string birthdate : date Class with attribute attribute second compartment of class Type & default Value are optional colon precedes type. Attribute name is left align & uses a lowercase letter name = Joe Joe:Person birthdate = 21 oct 1983 Object with values Value second compartment of object Use equal sign for value. 9

10 OPERATIONS & METHODS OPERATIONS :-Function applied to or by object Company Hire, Fire & pay bonus Window Open,close,hide,redisplay Same Operation applied to many different classes. Concept called?????? METHODS :- Implementation of operation for a class Ex:- Class File Print operation Implement Different methods to print ASSCII file, Binary file & picture file name Person birthdate changejob changeaddress File filename sizeinbyte lastupdate List operation 3 rd Compartment Opn name regular face Left align Lowercase letter print 10

11 SUMMARY OF NOTATIONS FOR CLASSES ClassName attributename1 : dataype1 = defaultvalue1 attributename2 : dataype2 = defaultvalue2 operationname1 (argumentlist1) : resulttype1 operationname2 (argumentlist2) : resulttype2 Notation for argument of operation Direction argumentname : type = defaultvalue name(parameter list) : type of value returned 11

12 Class Name Attributes Operation 12

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14 Links & Association Concepts Link Connection among object Instance of an instance. EX - Joe works for abc company tuple, that is a list of objects. instance of an association. Association Group of links with common structure & semantics Set of links in a class EX a person works for company UML Notation:-link line between objects If link have name it is underlined Association line between classes Arrange association from left to right 14

15 Examples of Association A Cup of Tea is drunk by one Person. A Person drinks zero or more Cups of Tea. Worksfor connects person to company Employs connects company to person REFERENCE :-It s a attribute in one object that refers to another object Ex:-Person object employer that refers to company Company Object employees that refers to Person 15

16 MULTIPLICITY how many instances of one class relate to instances of other class how many objects participate in a relationships Association or link? Class Dia. Country name HasCapital 1 1 CapitalCity name France:Country HasCapital Paris:CapitalCity Obj. Dia. name = France India:Country HasCapital name = Paris NewDelhi:CapitalCity name = India name = NewDelhi Canada:Country name= Canada HasCapital Ottawa:CapitalCity 16 name= Ottawa

17 Class Dia. Person name OwnsStock * * Company name Many-to-Many Association Class Dia. name Bank Account * 0.1 Zero-to-one Association Person name Class Dia. A Association * * * AnotherAssociation * B Obj Dia. ana:a alink anotherlink ab:b Association Vs Link 17

18 CARDINALITY :- Number of instances of each class involved Multiplicity constraint on size of a collection Cardinality Count of element that are actually in a collection Symbol Meaning 1 One and only one 0..1 Zero or one M N From M to N (natural integer) 0..* From zero to any positive integer 1..* 2..4 From one to any positive integer Specified range 18

19 ASSOCIATION END NAMES Multiplicity referred to end of association. Can give name to it. Ex:-one to many multiplicity one & end with multiplicity of many. Person name employee employer * WorksFor 0..1 Company name Employee employer joe TCS mary Infosys Useful for traversing association without explicitly mentioning association 19

20 Association end name are necessary for association between two objects of same class Distinguish multiple association between a pair of classes owner 1 User authorizeduser * * * Directory * 0..1 container contents All association end name attached to a class must be unique A directory may contain many lesser directories & may optionally be contained itself. 20

21 ORDERING Objects on many association end have no explicit order & used as set. Ex:-A screen containing no. of overlapping windows Screen {ordered} 1 VisibleOn * Window Each window on a Screen occurs at most one Only top most window is visible at any point on screen 21

22 BAGS & SEQUENCE binary association one link for a pair of objects permit multiple links for a pair of objects by annotating an association end with {bag} or {sequence} Bag collection of elements with duplicates allowed. Sequence ordered collection of elements with duplicates allowed 22

23 ASSOCISATION CLASS Ability to describe links of association with attributes like any class. An association class is an association that is also a class that have attributes & operations. 23

24 Figure represents attributes for two one-to-many & one-to-one association 24

25 Fig. shows how it is possible to fold att. For one-to-one & one-to-many association into class. This is not possible for many-to-many associations Multiplicity of association might changes. 25

26 Fig. shows association class participating in association User (authorized ) many workstations User has home directory for each workstation but several workstation & user can share same home directory User * * Workstation Authorization priority privileges * homedirectory 1 Directory startsession 26

27 QUALIFIED ASSOCIATION association in which an attribute called Qualifier disambiguates the objects for a many association end. A qualifier selects among the target objects, reducing the effective multiplicity from many to one. Both below models are acceptable but the qualified model adds information. 27

28 A stock exchange list many companies. It list only one company with given ticker symbol. A company may be listed on many stock exchange. 28

29 Generalization/Inheritance relationship between superclass & subclasses Organizing the classes By similarities differences, structuring the descriptions of objects. A superclass holds common attributes, operations and associations. A subclass may: inherits its parent s attributes, operations, and relationships Add additional attributes, operations,relationships They inherit the features of their superclass. Generalization is called a IS A relationship 29

30 a subclass inherits from one or more superclasses Single inheritance Multiple inheritance Ancestor Superclass (parent) Example: Single Inheritance Account balance name number Withdraw() CreateStatement() Generalization Relationship Subclasses Checking Withdraw() Descendents Savings GetInterest() Withdraw() 30

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32 Use of generalization Support of polymorphism: polymorphism increases the flexibility of software. Adding a new subclass and automatically inheriting superclass behavior. Structuring the description of objects: Forming a taxonomy (classification), organizing objects according to their similarities. It is much more profound than modeling each class individually and in isolation of other similar classes. Enabling code reuse: Reuse is more productive than repeatedly writing code from scratch. 32

33 Generalization : - superclass generalize the subclasses Specialization :- subclasses refine or specialize the superclass Inheritance :- it s a mechanism for sharing of attributes, operations & association 33

34 OVERRIDING FEATURE A subclass may override a superclass feature (attribute default values, operation) by redefining a feature with the same name. Never override the signature of methods. 34