Hierarchical Inheritance − A class has a number of subclasses each of which may have subsequent subclasses, continuing for a number of levels, so as to form a tree structure. They are collected over all projects over long periods of time. Representation in DFD − A data store is represented by two parallel lines containing the name of the data store. According to the theories of abstract data type, a type is a characterization of a set of elements. After the analysis phase, the conceptual model is developed further into an object-oriented model using object-oriented design (OOD). We depicted this in terms of a “warp and woof” diagram for cloth: Major functions Major Types of Data c) Thus, a key part of solving any problem is identifying the classes that naturally model its domain. Data stores are the passive objects that act as a repository of data. Aggregation - "has-a" relationship In UML, aggregation is deifned as a special form of association (an association is a structural relationship that specifies that objects are connected to other objects) that specifies a whole-part relationship between the aggregate (whole) and a component part. Subsystem tests can be used as regression tests for each newly released version of the subsystem. A class can have its objects or may inherit from other classes. Activities are shown in activity diagrams that portray the flow from one activity to another. This is the purpose of dynamic modelling. The following figure depicts the examples of different types of inheritance. A whole system can be visualized as a high-level process. Any object-oriented programming language like C++, Java, Smalltalk, C# and Python, includes provision for representing classes. A module should have low coupling with other modules, i.e., interaction or interdependence between modules should be minimum. There are two types of design models that need to be produced −. Signal Event − A named object thrown by one object and caught by another object. An aggregate object is an object that is composed of one or more other objects. Let us consider two classes, Circle and Square, each with a method findArea(). DFDs illustrate the series of transformations or computations performed on the objects or the system, and the external controls and objects that affect the transformation. Grady Booch has defined object-oriented design as “a method of design encompassing the process of object-oriented decomposition and a notation for depicting both logical and physical as well as static and dynamic models of the system under design”. The attributes of Circle are x-coord, y-coord, and radius. Now, we will look at the relative advantages and disadvantages of structured analysis approach and object-oriented analysis approach. Message passing between two objects is generally unidirectional. In this chapter, we exemplify the concept using C++. An actor represents the roles that the users of the use cases play. In the generalization process, the common characteristics of classes are combined to form a class in a higher level of hierarchy, i.e., subclasses are combined to form a generalized super-class. They do not throw any light on the frequency of computations or the reasons for computations. In object-oriented modeling, the three most important relationships are dependencies, generalizations, and associations. In Dynamic Modelling, the constraints define the relationship between the states and events of different objects. The dynamic model shows the status of the objects and the operations performed on the occurrences of events and the subsequent changes in states. Relationship among objects. Private − A private member is visible only from within the class. For example, consider the association between Department and Employee −, To implement M:N associations, a new relation is created that represents the association. Ideally, you may illustrate the flow of the association by utilizing a directed association. Generalization relationships appear in class, component, and use-case diagrams. Functional Modelling gives the process perspective of the object-oriented analysis model and an overview of what the system is supposed to do. Modularity can be visualized as a way of mapping encapsulated abstractions into real, physical modules having high cohesion within the modules and their inter–module interaction or coupling is low. As with classes of objects, event classes may also be organized in a hierarchical structure. During instantiation, values are assigned for at least some of the attributes. Implementation using C++ −. The following figure shows the events in a state machine. Concepts related to concurrency within an object are as follows −. Generalization: also called an "is-a-kind-of" relationship. In composition relationship both entities are interdependent of each other for example “engine is part of car”, “heart is part of body”.Let us take an example of car and engine. Most programming languages do not provide constructs to implement associations directly. It should instead be accessed through the methods setValues() and getValues(). A process may be further divided into smaller components. The active objects synchronize with one another as well as with purely sequential objects. Notations − In these diagrams, the objects that participate in the interaction are shown using vertices. An aggregate object is an object that is composed of one or more other objects. ExampleLet us take an example of “Student” and “address”. A link represents a connection through which an object collaborates with other objects. Once the code is in shape, it is tested using specialized techniques to identify and remove the errors in the code. A sub-state is a state that is nested inside another state. It is often seen that a perfectly optimized design is more efficient but less readable and reusable. Concurrency in operating systems allows performing multiple tasks or processes simultaneously. When a part of the information is to be retrieved, the output arrow is labelled. They are the ongoing executions within a system that can be interrupted. This is implemented by including in Department, an object of Manager that should not be NULL. Optional or one–to–one Associations − Consider the relationship between Project and Project Manager having one–to–one bidirectional association as shown in the figure below. In the next level DFD, as shown in the following figure, the major processes of the system are identified, the data stores are defined and the interaction of the processes with the actors, and the data stores are established. The second figure portrays the aggregation relationship, a University is the “whole–of” many Departments. When identifying relationships, start with the class that interacts with as many other classes as possible; perhaps, the core classes of the application. Two versions of myheader.h are shown, tracing from the recent version to its ancestor. See the following figures. The Find Total Sales process computes the yearly total sales corresponding to each customer and records the data. Activities result in actions which are atomic operations. Stereotypes − It extends the vocabulary of the UML, through which new building blocks can be created out of existing ones. From the class Account, two classes have inherited, namely, Savings Account and Current Account. For example, we can consider the events of departure of a flight of an airline, which we can group into the following class −, Flight_Departs (Flight_No, From_City, To_City, Route). For example, Department and Manager have one–to–one association as shown in the figure below. In the system, three processes can be identified, which are −, The data stores that will be required are −. There are two categories of elements in an object-oriented system −, Major Elements − By major, it is meant that if a model does not have any one of these elements, it ceases to be object oriented. The object-oriented paradigm took its shape from the initial concept of a new programming approach, while the interest in design and analysis methods came much later. An object occupies a memory space and exists for a particular period of time. But an object by itself … - Selection from Learning Java [Book] Data Flows − Data flows to or from actors represent operations on or by objects. 1994) (a) (b) ^ (c) (id) 9. There are three processes in it, Verify Details, Generate C_Code, and Update Customer Details. Besides, the developer designs the internal details of the classes and their associations, i.e., the data structure for each attribute and the algorithms for the operations. Division of Interface and Implementation − An interface defines the rules for interaction. In software engineering, 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. Events have a location in time and space but do not have a time period associated with it. Aggregation is referred as a “part–of” or “has–a” relationship, with the ability to navigate from the whole to its parts. The system design phase needs to address the initialization and the termination of the system as a whole as well as each subsystem. Representation − A constraint is rendered as a string within braces. and H.C.F. To enable concurrency, each concurrent element is assigned a separate thread of control. Object-oriented decomposition identifies individual autonomous objects in a system and the communication among these objects. Dependency: also called a using relationship, which means, one class is dependent on another class. An object may have states that are composed of sub-states, and concurrent events may occur in each of the sub-states. The following figure shows the notations of an actor named Student and a use case called Generate Performance Report. This will be a aggregation relationship. In relational database management systems (RDBMS), data is stored as relations or tables, where each column or field represents an attribute and each row or tuple represents a record of an instance. A transition forms an input statement, the main control path forms the sequence of instructions, the branches form the conditions, and the backward paths form the loops or iterations. This is implemented by including a list of Dependents in class Employee. The following figure shows an example of generalization and specialization. In UML, behind each graphical notation, there is a textual statement denoting the syntax and semantics. Methods per Class − It determines the complexity of a class. So Student work as owner entity. Grouping Things − They comprise the organizational parts of the UML models. There are two primary diagrams that are used for dynamic modelling −, Interaction diagrams describe the dynamic behavior among different objects. The relationship may be found within a group of tuples which are typed However it may have additional details about the contents of the package. Aggregation is a one way association. The following metrics are appropriate for object-oriented software projects −, Product metrics measure the characteristics of the software product that has been developed. There is at most one initial state and one final state in these state machines. Terms such as superclass, subclass, or inheritance come to mind when thinking about the object-oriented approach. A relationship is an association between classes. The important features of object–oriented programming are −. To map inheritance, the primary key of the base table(s) is assigned as the primary key as well as the foreign key in the derived table(s). Object modelling develops the static structure of the software system in terms of objects. Event class indicates a group of events with common structure and behavior. Generalization − This represents a generalization/specialization relationship in which subclasses inherit structure and behavior from super-classes. The system allows the manager to manage customer accounts and answer any queries posted by the customer. “PART–OF” hierarchy − It defines the hierarchical relationship in aggregation by which a class may be composed of other classes. The primary scenarios depict the essential sequences and the secondary scenarios depict the alternative sequences. The databases are created and the specific hardware requirements are ascertained. For implementation, an object of Current Account is included as an attribute in Customer that may be NULL. 3 II. Activity is an operation upon the states of an object that requires some time period. Here, each of the forked components is labelled. An object is represented as a rectangle with two sections −, The top section contains the name of the object with the name of the class or package of which it is an instance of. Additional information about the relationship could be obtained by attaching the association relationship with the association class. It is a specific kind of Whole-Part relationship. Software quality assurance is a methodology that determines the extent to which a software product is fit for use. 13. enumeration An enumeration is a data type that has a finite set Acceptance testing − This is carried out by the customer before accepting the deliverables. A two-way arrow implies both retrieval and update. are the output data flows. For example is “Apple is a fruit”, “Ferrari is a car”.For better understanding let us take a real world scenario. Once a program code is written, it must be tested to detect and subsequently handle all errors in it. Objects in different processes can be involved in message passing. Besides, each association may be either one–to–one, one–to–many, or many–to–many. ooad Architectural modeling mcq,ooad mcq,ooad multiple choice questions with answers,ooad objective questions,ooad bits,ooad mid-2 questions with answers,jntuh ooad mid-2 paper,jntuh cse 3-2 mid-2 papers,ooad it ooad mid-2 question paper, ooad it 3-2 mid-2 papers,object oriented analysis and design mid-2 papers,indianonlineviews,csestudyzone,cse study zone,jntuh mid … The different aspects that are documented are as follows −. Interface realization An interface realization relationship is a The extensibility mechanisms are −. So, the time and cost of development is inherently high. Aggregation is a special form of association. Collaboration Diagram − It represents the structural organization of objects that send and receive messages through vertices and arcs. The transition gives the relationship between the first state and the new state. Example − Collaboration diagram for the Automated Trading House System is illustrated in the figure below. These are the patterns of design. In traditional programming, the lifespan of an object was typically the lifespan of the execution of the program that created it. One of the advantages of Object-Oriented programming language is code reuse. All the interfaces between the objects cannot be represented in a single diagram. In the ensuing editions, he extended his ideas to a complete object–oriented design method. Message passing essentially involves invoking class methods. Entry action is the action that is executed on entering a state, irrespective of the transition that led into it. The state is an abstraction given by the values of the attributes that the object has at a particular time period. There may be more than one algorithm corresponding to a given operation. relationships among classes/objects: generalization/specialization (inheritance),aggregationand association.These are certainly not new concepts and most professionals work … They are used as a part of the system documentation. A set of attributes for the objects that are to be instantiated from the class. By default, an association that exists between classes is bi-directional. Example − Let us consider the Circle class introduced earlier. The dynamic context describes how the system interacts with its environment. In this stage, the design model developed in the object design is translated into code in an appropriate programming language or software tool. State transition diagrams or state machines describe the dynamic behavior of a single object. Inheritance:Inheritance is “IS-A” type of relationship. Example − The following figure shows a process Compute_HCF_LCM that accepts two integers as inputs and outputs their HCF (highest common factor) and LCM (least common multiple). Object–Oriented Design (OOD) involves implementation of the conceptual model produced during object-oriented analysis. It allows effective management of software complexity by the virtue of modularity. Unit testing is the responsibility of the application engineer who implements the structure. UML includes nine diagrams in all, namely −, UML has a number of rules so that the models are semantically self-consistent and related to other models in the system harmoniously. These Boolean values are called the control flows. the control flow of organization using collaboration diagrams. Data flows to or from data stores represent queries or updates. Time Event − An event representing passage of time. Testing starts from the individual classes to the small modules comprising of classes, gradually to larger modules, and finally all the major subsystems. Behavioral Things − These are the verbs of the UML models representing the dynamic behavior over time and space. The messages that these objects send and receive are placed along the y–axis, in the order of increasing time from top to bottom. Input to the data store comprises of details of sales such as item, billing amount, date, etc. The structural things are class, interface, collaboration, use case, active class, components, and nodes. Polymorphism is particularly effective while implementing inheritance. In addition, each has its own particular characteristics. The main concepts are −. Once the alternative algorithms are identified, the optimal algorithm is selected for the given problem domain. To map a class to a database table, each attribute is represented as a field in the table. In this stage, the problem is formulated, user requirements are identified, and then a model is built based upon real–world objects. In the 1990s, Coad incorporated behavioral ideas to object-oriented methods. have defined DFD as, “A data flow diagram is a graph which shows the flow of data values from their sources in objects through processes that transform them to their destinations on other objects.”. Each of the state machines has its own initial and final states. If it is not zero, the control flow OK has a value True and subsequently the Divide process computes the Quotient and the Remainder. The following figure gives the notation of an interface. The dynamic model represents the time–dependent aspects of a system. It preserves inherent concurrency of real objects. Presence of too many associations may render a system indecipherable and hence reduce the overall efficiency of the system. Some of the important types of grey box testing are −. It allows objects to be placed directly within the body of other classes. A link depicts the relationship between two or more objects. Degree may be unary, binary, or ternary. If one concurrent sub-state reaches its final state before the other, control waits at its final state. It comprises of the classes, interfaces, and collaborations of a system; and the relationships between them. An action may operate upon an object on which an event has been triggered or on other objects that are visible to this object. Example − The following figure shows the actors, namely, Customer and Sales_Clerk in a counter sales system. They are used as indicators for long-term software process improvements. Each year, the shop distributes Christmas gifts to its customers, which comprise of a silver coin or a gold coin depending upon the total sales and the decision of the proprietor. A package may contain structural things like classes, components, and other packages in it. Key abstractions and mechanisms − Class diagrams and object diagrams. Bank, Branch, Account, Savings Account, Current Account, Loan, and Customer. Here, the distinguishing features of groups of objects are used to form specialized classes from existing classes. If two operations of a single object are concurrent in nature, then that object is split among different threads. Call Event − A synchronous event representing dispatch of an operation. The implementation details generally include −. Public − A public member is visible from anywhere in the system. Classes and subclasses are grouped together to show the static relationship between each object. An object is the concrete instance that has actual existence in the system. A state machine is graphically represented through a state transition diagram. While designing applications, some commonly accepted solutions are adopted for some categories of problems. Through hierarchy, a system can be made up of interrelated subsystems, which can have their own subsystems and so on until the smallest level components are reached. So, during optimization, all non-usable associations are removed. For example, in the association between Customer and Current Account in the figure below, a customer may or may not have a current account. Implementation using C++ −. The other significant innovations were Object Modelling Techniques (OMT) by James Rumbaugh and Object-Oriented Software Engineering (OOSE) by Ivar Jacobson. A class represents a collection of objects having same characteristic properties that exhibit common behavior. The main difference between object-oriented analysis and other forms of analysis is that in object-oriented approach, requirements are organized around objects, which integrate both data and functions. The objects identified during analysis are etched out for implementation with an aim to minimize execution time, memory consumption, and overall cost. In object-oriented modeling, the four most important relationships are dependencies, generalizations, associations, and … Let us consider an Automated Trading House System. UML behavioral diagrams visualize, specify, construct, and document the dynamic aspects of a system. System − A set of elements organized to achieve certain objectives form a system. An actor may be a person (e.g. What Is the Difference Between Classes and Objects? Physical containment − Example, a computer is composed of monitor, CPU, mouse, keyboard, and so on. The following figure shows the corresponding class diagram. It gives the blueprint or description of the objects that can be created from it. relationship. So the designer must strike a balance between the two. During system design, the events that may occur in the objects of the system need to be identified and appropriately dealt with. The start–up of the system, i.e., the transition of the system from non-initialized state to steady state. They represent a data structure, a disk file, or a table in a database. The former is the independent thing, while the latter is the dependent thing. Object-oriented design includes two main stages, namely, system design and object design. In this chapter, we will look into the basic concepts and terminologies of object–oriented systems. A number of schemes are used for testing purposes. UML is an open-ended language. It identifies the objects, the classes into which the objects can be grouped into and the relationships between the objects. Notation − Graphically, a package is represented by a tabbed folder. Object modelling develops the static structure of the software system in terms of objects. The four major elements are −, Minor Elements − By minor, it is meant that these elements are useful, but not indispensable part of the object model. Schulmeyer and McManus have defined software quality as “the fitness for use of the total software product”. Beta testing − This is carried out by select group of co-operating customers. It is a situation occurring for a finite time period in the lifetime of an object, in which it fulfils certain conditions, performs certain activities, or waits for certain events to occur. Now, if the operation scale() is performed on my_circle with a scaling factor of 2, the value of the variable a will become 8. One–to–One − A single object of class A is associated with a single object of class B. One–to–Many − A single object of class A is associated with many objects of class B. Many–to–Many − An object of class A may be associated with many objects of class B and conversely an object of class B may be associated with many objects of class A. Aggregation or composition is a relationship among classes by which a class can be made up of any combination of objects of other classes. In the 1980s, Grady Booch published a paper titled Object Oriented Design that mainly presented a design for the programming language, Ada. The main actions are expanded to data flow diagrams. It can be upgraded from small to large systems at a greater ease than in systems following structured analysis. The system is conceived as a set of interacting subsystems that in turn is composed of a hierarchy of interacting objects, grouped into classes. Strong Typing − Here, the operation on an object is checked at the time of compilation, as in the programming language Eiffel. Process metrics help in measuring how a process is performing. Inheritance is the mechanism that permits new classes to be created out of existing classes by extending and refining its capabilities. The lowest-level process may be a simple function. Through encapsulation, the internal details of a class can be hidden from outside. System Architecture − The system architecture is designed on the basis of the context of the system in accordance with the principles of architectural design as well as domain knowledge. Portability − Portability determines whether the software can operate in different platforms with different hardware devices. Control as Concurrent Tasks − In this approach, an object is implemented as a task in the programming language or the operating system. For this assumption we can create a “StaffMember” parent class and inherit this parent class in “HOD” and “Teacher” class. The final state indicates the completion of execution of the state machine. It helps to visualize, specify, construct, and document the artifacts of an object-oriented system. The state transition diagram of each object in the system is developed. With each update of the base attribute value, the derived attribute is also re-computed. It allows objects to be placed directly within the body of other classes. Identify whether an association is unidirectional or bidirectional. The following figure shows the expansion of the process Ascertain Gifts. The metrics for choosing the optimal algorithm are −. Implementation using C++ STL list container −. An operation specifies what is to be done and not how it should be done. Interaction diagrams depict interactions of objects and their relationships. Target State − The destination state after completion of transition. To avoid this, the following steps are taken −. Scenario is a description of a specified sequence of actions. Event, an occurrence that triggers transitions, Action, an uninterrupted and atomic computation that occurs due to some event, and. State model based testing − This encompasses state coverage, state transition coverage, and state transition path coverage. A process is decomposed into sub-processes, the data flows among the sub-processes are identified, the control flows are determined, and the data stores are defined. Let us take first two assumptions , “HOD is a staff member of college” and “All teachers are staff member of college”. Operations are also referred as functions or methods. Actors − Actors are the objects in the object model. The initial configuration of the system and the reconfiguration of the system when needed.
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