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![Inheritance
It is the sharing of attributes and operations among
classes based on a hierarchical relationship.
Super class has general information.
Subclasses can be formed from broadly defined
class[Super class].
Each subclass incorporates or inherits all the
properties of its super class and adds its own unique
properties.](https://image.slidesharecdn.com/oomdunit1-190427094255/85/Oomd-unit1-17-320.jpg)
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Oomd unit1
- 1. TEXT BOOKS: •Object-Oriented Modeling and Design with UML - Michael Blaha, JamesRumbaugh , 2nd Edition, Pearson Education, reprint 2013. •Frank Buschmann, Regine Meunier, Hans Rohnert, Peter Sommerlad, Michael Stal: Pattern-Oriented Software Architecture, A System of Patterns, Volume 1, John Wiley and Sons, 2007. •Stephan H. Kan: Metrics and Models in Software Quality Engineering, 2nd Edition, Pearson.
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- 4. Introduction It is anew way of thinking about problems using models based on real world concepts. The basic construct is object which combines both data structure and behavior in a single entity. Rambaugh presents an object oriented software development methodology, the Object Modeling Technique (OMT) which extends from analysis through design to implementation.
- 5. Analysis model isbuilt to abstract essential aspects of application domain which contains objects found in application, their properties and behavior. Then design model is made to describe and optimize the implementation. Finally the design model is implemented in a programming language, database or hardware. Graphical notation is used for expressing object- oriented models.
- 6. OBJECT ORIENTED CONCEPTS OBJECT Objects are the physical and conceptual things that exist in the universe. In programming terms, an object is a self-contained component that contains properties and methods needed to make a certain type of data useful. Object is an instance of a class. CLASS A class is a blueprint or template or set of instructions to build a specific type of object. In programming terms, a class is a way to bind, data and functions into a single unit. A class is an abstraction that describes important properties of object.
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- 10. What is object-oriented? Object Oriented(OO): Softwareis organized as a collection of discrete objects that incorporate both data structure and behavior. In general it includes 4 aspects- identity, classification, inheritance and polymorphism.
- 11. Identity Identity means thatdata is organized into discrete, distinguishable entities called objects. Objects can be concrete or conceptual. In real world an object simply exist but within a programming language each object has a unique handle by which it can be uniquely referenced. The handle can be implemented by address, array index or unique value of an attribute.
- 12. Classification It means thatobjects with same data structure (attribute) and behavior (operations) are grouped into a class. A class is an abstraction that describes important properties and ignores the rest. Each class describes a possibly infinite set of individual objects. Object is an instance of its class. An object has its own value for each attributes but shares the attribute name and operations with other instances of the classes.
- 13. Objects and classes Polygonobjects Polygon Classes Attributes vertices boarder color Operations Draw Erase Move rectangle parallelogram trapezoid
- 15. Polymorphism It means thatthe same operation (i.e. action or transformation that the object performs) may behave differently on different classes. An operation is a procedure or transformation that the object performs. Specific implementation of an operation by a certain class is called a method.
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- 17. Inheritance It is thesharing of attributes and operations among classes based on a hierarchical relationship. Super class has general information. Subclasses can be formed from broadly defined class[Super class]. Each subclass incorporates or inherits all the properties of its super class and adds its own unique properties.
- 18. Object-oriented development? The themeis the identification and organization of application concepts rather than final representation in a programming Language. OOD approach encourages software developers to work and think in terms of the application domain through most of the software engineering life cycle. It is a conceptual process independent of a programming language until the final stage.
- 19. Object-oriented methodology Object OrientedMethodology is a methodology for object oriented development and a graphical notation for representing objects oriented concepts. We can call this methodology as OMT. The methodology has the following stages: System Conception Analysis System design Class design Implementation
- 20. System conception Software developmentbegins with business analysts or user conceiving an application and formulating tentative requirements. Analysis – The analyst scrutinizes and restate the requirements from conception by constructing model. An analysis model is a concise, precise abstraction of what the desired system must do, not how it will be done. It should not contain any implementation details. The objects in the model should be application domain concepts and not the computer implementation concepts. Analysis model has two parts: Domain model: a description of the real world objects reflected with in the system. Application model: a description of the parts of the application system itself that are visible to the user.
- 21. System design – Thedesigner makes high level decisions about the overall architecture. In system design, the target system is organized as various subsystems based on both the analysis structure and the proposed architecture. System designer must decide what performance characteristics to optimize, choose strategy of attacking the problem, and make the resource allocations.
- 22. Class design – Designeradds details to the analysis model in accordance with the system design strategy. Elaborate both domain and application objects. Focus is on data structures and algorithms needed to implement each class.
- 23. Implementation – The objectclasses and relationships developed during object design are finally translated into a particular programming language, database, or hardware implementation. During implementation, it is important to follow good software engineering practice so that the system can remain the traceability, flexibility and extensibility.
- 24. 3 models Three kindsof models to describe a system from different viewpoints Class model State model Interaction model
- 25. Class model Describes basicstructure of objects and their relationship Contains class diagram Class diagram is a graph whose nodes are object classes (Classes) and whose arcs are relationships among classes.
- 26. State model Describes theaspects of a system that change over time. It specifies and implement control aspects of a system. Contains state diagram. State diagram is a graph whose nodes are states and whose arcs are data-flows.
- 27. Interaction Model Describes howthe objects in a system cooperate to achieve border result Contains Use Case, Sequence diagram and activity diagram. Use case focuses on the functionality of a system – that is what a system does for a user. Sequence diagram shows the object that interact and the time sequence of their interaction. Activity diagram elaborate important processing steps.
- 28. OO themes Abstraction Encapsulation Combining dataand behavior Sharing Emphasis on the Essence of an object Synergy
- 30. Abstraction It consists offocusing on essential aspects of an entity and ignoring accidental properties. The goal is to isolate those aspects that are important for some purpose and suppress those aspects that are unimportant. Abstraction must always for some purpose because the purpose determines what is and what is not important. Many different abstractions of same thing are possible, depending on the purpose for which they are made. In building models, one must not search for absolute truth but for adequacy for some purpose. A good model captures the crucial aspects of a problem and omits the others. Focus on what an object is and does, not how to implement.
- 33. Encapsulation Information hiding Separating externalaspects of an object which are accessible to other objects, from the internal implementation details of the object, which are hidden from other objects. The implementation of an object can be changed without affecting the applications that use it. Encapsulation- combine data structures and behavior in a single entity.
- 34. Combining Data andBehavior • Caller of an operation need not consider how many implementations of a given operation exist. • Operator polymorphism shifts the burden of deciding what implementation to use from the calling code to the class hierarchy. • As an example, let us talk about an object oriented program calling a draw procedure for drawing different figures say a polygon, circle, or text. • The decision of which procedure to use is made by each object, based on its class. • Maintenance is easier.
- 35. Sharing • Inheritance ofboth data structure and behavior lets subclasses share common code • The sharing of code using inheritance is one of the main advantages of object oriented languages. • OO development also offers the prospect of reusing designs and code on future projects.
- 36. Synergy Identity, Classification, polymorphismand inheritance can be used in isolation but together they complement each other synergistically.
- 37. Modeling A model isan abstraction of something for the purpose of understanding it before building it. The word model has 2 dimensions- a view of a system ( Class, state or interaction model) and a stage of development ( analysis, design or implementation)
- 38. Model serves severalPurpose – Testing a physical entity before building it : Recent advances in computation permit the simulation of many physical structures without the need to build physical models. Simulation is cheaper. Both physical model and computer model are cheaper than building a complete system and enable early correction of flaws. Communication with customers Architects and product designers build models to show their customers. Mock-ups are demonstration product that imitate some or all of the external behavior of a system. Visualization Storyboards of movies, television shows and advertisements let writer see how their ideas flow. They can modify awkward transitions, dangling ends, and unnecessary segments before detail writing begins. Reduction of complexity Modeling deal with systems that are too complex to understand directly.
- 39. Three ModelsClass Model Itrepresents the static, structural ,”data” aspects of a system. It describes the static structure of objects in a system- their identity, relationship to other object, attribute and operations. It provides context for state and interaction model. our goal is to capture those concepts from real world that are important to an application. Class diagram express the class model. The important concepts in class model are classes, association and generalizations.
- 40. State model It representsthe temporal, behavioral, ”control” aspects of a system. Describes the aspects of objects concerned with time and the sequencing of operation-events that mark changes, states that define the context for event and organization of state and event. Control aspects of a system describe the sequence of operations that occur. State diagram express the state model.
- 41. Interaction Model Describes theinteraction between objects. How the objects in a system cooperate to achieve border result. It represents the collaboration of individual objects, the ”interaction” aspects of a system. Use case focuses on the functionality of a system – that is what a system does for a user. Sequence diagram shows the object that interact and the time sequence of their interaction. Activity diagram elaborate important processing steps.
- 42. Relationship among theModels Each describe one aspect of the system but contains references to the other model. Class model describes properties and behavior on which the state and interaction model operate. State model shows decisions that depend on object value ,the decisions causes changes in object value and subsequent states. Interaction model provide overview of the operation of a system.
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- 44. Object and Classconcepts Objects Define objects as a concept, abstraction or thing with identity that has meaning for an application. All objects have identity and are distinguishable.eg:- Two apples can be described as 2 different objects even though they have the same descriptive properties. Classes An object class describes a group of objects with similar properties (attributes), behavior (operations), relationships to other objects and semantics.
- 45. There are twokinds of models of structure Class diagram: It provides a graphical notation for modeling classes and their relationship, thereby describing possible objects. UML symbol for class is a box. List class name in boldface, center the name in the box, and capitalize the first letter. Class diagrams are useful both for abstract modeling and designing actual program. Person Company
- 46. Object diagram It showsindividual objects and their relationship. A class diagram can have infinite set of object diagram. UML symbol for object is a box with an object name followed by a colon and class name. the object and class name are both underlined. JoeSmith: Person Adam: Person :Person TCS: Company IBM: Company
- 47. Values and Attributes AValue is a piece of data. An attribute is a named property of a class that describes a value held by each object of the class. Each attribute name is unique within a class. An attribute should be a pure data value, not an object. Person name: string age: integer birthdate: date JoeSmith:Person name: “JoeSmith” age: 20 birthdate: 1 Jan 1993 Adam:Person name: “Adam” age: 21 birthdate: 1 Jan 1992 Class with Attributes Objects with Attributes
- 48. Class with Attributes UMLnotation lists attributes in the second compartment of the class box. Optional details, such as type and default value, may follow each attribute in class box. A colon precedes the type and equal sign precedes the default value. List attribute name in regular face, left aligned and use a lowercase letter for the first letter. Object with values UML notation includes attributes values in the second compartment of the object box. list each attribute name followed by an equal sign and the value. And left align attributes values and use regular type face.
- 49. In class model,object identifiers are implicit in model-need not and should not list them explicitly. Person personID:ID name: string age: integer birthdate: date Person name: string age: integer birthdate: date Wrong Correct
- 50. Operations and Methods Anoperation is a function or procedure that may be applied to or by objects in a class. All objects in a class share the same operations. The same operation may apply to many different classes. Such an operation is polymorphic i.e. the same operation takes on different forms in different classes. A method is the implementation of an operation for a class. When an operation has methods on several classes, all methods must have same signature.
- 51. UML notation listsoperations in the third compartment of the class box. List operation name in regular face, left aligned and use a lowercase letter for the first letter. Optional details, operation name followed by argument list enclosed in parenthesis, commas separates the argument and a colon precedes the result type. Return type of operation is also optional may follow each argument list. Person name age birthdate netSalary File fileName sizeInBytes lastUpdate print GeometricObject color Position move(delta: Vector) select(p: Point): Boolean rotate(in angle: float=0.0)
- 52. Links and AssociationConcepts Links and associations are the means for establishing relationships among objects and classes. A link is a physical or conceptual connection between objects. A link is an instance of an association. An association describes a group of links with common structure and semantics. All the links in an association connect objects from the same classes. Association and links often appear as verbs in a problem statement. An association describes a set of potential links in the same way that a class describes a set of potential objects.
- 53. Associations are bidirectional. Inreal, both directions of traversal are equally meaningful and refer to same association. Associations are often implemented in programming languages as pointers from one object to another. A pointer is an attribute in one object that contains an explicit reference to another object. A link shows a relationship between two or more objects. All connections among classes should be modeled as association. One-to-one association Many-to-many association Ternary association
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- 55. Multiplicity It specifies howmany instances of one class may relate to a single instance of an associated class. Multiplicity depends upon assumptions and how you define the boundaries of a problem.
- 56. Multiplicity Multiplicity specifies howmany instances of one class may relate to each instance of another class. Fig one-to-one association UML list multiplicity at the end of association lines. UML specifies multiplicity with an interval, such as ‘1’,’1….*’,or ‘3…5’. Multiplicity is a constraint on the size of a collection; Cardinality is the count of elements that are actually in a collection. Therefore, multiplicity is a constraint on Cardinality Country name CapitalCity name HasCapital 1 1
- 57. Workstation Window console 1 0..1 FigZero-or-one multiplicity
- 58. Association End Names Itis the name given to end of association. UML specifies association end name next to association end. Use of end names is optional. Association end name appear as noun in problem description. It provides a means of traversing an association. Association end name are necessary for associations between two objects of the same class. It also distinguish multiple associations between a pair of classes. It let you unify multiple references to same class. All the names must be unique because it distinguish objects. Person Company WorksFor employee employer * 0…1
- 59. User Dictionary owner contents container authorized user 10..1 * * * * •In Figure, container and contents distuinguish the two usages of directory in the self –association. •A dictionary may contain many lesser directories and may optionally may contained itself. •Association end name can also distuinguish multiple association between the same pair of classes. • In Figure each directory has exactly one user who is an owner and many users who are authorized to use the directory.
- 60. Association end namelet you unify multiple references to same class. When constructing class diagram, should properly use Association end names and to introduce separate class for each reference. Parent Child 2 * Person child * Parent 0…2 Wrong Model Correct Model
- 61. Ordering Sometimes, the objectsare explicitly ordered. For example, the figure below shows a workstation screen containing a number of overlapping windows. The windows are explicitly ordered, so only the topmost window is visible at any point on the screen. Screen Window *1 {ordered} Fig .Ordering the objects for an association end visibleOn
- 62. Bags and Sequences Multiplelinks for a pair of objects are permitted by annotating an association end with {bag} or {sequence}. A bag is a collection of elements with duplicates allowed. A sequence is an ordered collection of elements with duplicates allowed. Itinerary Airport ** {Sequence} Fig .An example of a sequence
- 63. Association Classes An associationClass is an association that is also a class UML notation for an association Class is a box attached to the association by a dashed line. File User ** Fig .An example of a sequence AccessibilityBy accessPermissio n
- 64. User Workstatio n** Authorization priority privilege startSession Directory * 1 homedirector y Person name Purchase quatity date cost Company name*1stock * 1 ** OwnsStock quantity Person name Company name Association Class ordinary Class
- 65. Qualified Associations Qualified associationis an association in which an attributes called the qualifier disambiguates the object for a “many” association end. A qualifier selects among the target objects, reducing the effective multiplicity, from “many” to “one”. UML notation for a qualifier is a small box on the end of an association line near the source class. Qualifier box may grow out of any side. Bank Account accnum 1 * Fig . Not qualified Bank Accountaccnum Fig . Qualified 1 0..1
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- 67. Generalization and Inheritance Generalizationis a relationship between a super class and subclass. Each subclass is said to be inherit the features of its super class. It is “is-a” relationship because each instance of a sub class is an instance of super class as well. UML notation for a generalization is a large hollow arrowhead. The arrowhead points to the super class. Super class may directly connect to each subclass, but normally prefer to group subclass as a tree. A generalization set name is an enumerated attribute that indicates which aspect of an object is being abstracted by a particular generalization.
- 68. Fig. Inheritance forgraphic figure Figure color centerPosition penThickness penType move select rotate display ZeroDimensional OneDimensional orientation scale TwoDimensional Orientation fillType scale fill Line endPoint display Point display Arc radius startAngl e arcAngle display Spline controlPt s display Polygon numOfSide s vertices display Circle diameter display rotate dimentionality
- 69. Use of generalization Generalizationhas three purpose. 1. It support for polymorphism. 2. It structure the description of objects. 3. It enable reuse of code. The word generalization derives from the fact that the superclass generalizes the subclass. The word specialization refers to the fact that the subclass refine or specialize the superclass. Inheritance is the mechanism for sharing attributes, operations and association via the generalization/ specialization relationship.
- 70. Overriding features A subclassmay override a superclass feature by defining a feature with the same name. The overriding features(the subclass feature) refines and replaces the overridden feature(the superclass feature) . Method and default values of attribute can be override, but never override the signature of a feature. An overriding should preserve attribute types, number and type of arguments to an operation, and operation return type.
- 71. Navigation of classmodels Navigation is important because it lets you exercise a model and uncover hidden flaws and omissions so that you can repair them. It is possible to perform navigation manually or write navigation expressions. UML incorporates a language that express several kinds of question asked on model—object constraint language(OCL)
- 72. OCL constructs fortraversing class model Attributes Operations Simple Association Qualified Association Generalization Filters Refer TB for credit card related class diagram. OCL queries in next few slides are written for that diagram.
- 73. Use OCL toanswer credit card Questions. What transaction occurred for a credit card account within a time interval. aCreditCardAccount.Statement.Transaction ->select (aStartDate <= transactionDate and transactionDate <= anEndDate )
- 74. What volume oftransanctions held by an institution in the last year? anInstitution.CreditCardAccount.Statement.Transaction -> select(aStartDate <= transactionDate and transactionDate <= anEndDate ).amount -> sum() How many credit card account does a customer currently have? aCustomer.MailingAddress.CreditCardAccount -> size() What is the total maximum credit for a customer, for all accounts? aCustomer.MailingAddress.CreditCardAccount .maxmumCredit-> sum()