Object Oriented Modeling and Design [PDF]

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MODULE 1 What is object oriented modeling and design? Object-Oriented Modeling and Design (OOMD) is a software design approach that focuses on creating models based on objects, rather than just functions and logic. It involves representing real-world objects and their behavior as software objects and creating relationships between them to model a system. For example, consider a simple model of a car. In object-oriented design, you could represent the car as a software object with properties such as make, model, color, and speed. The car object could also have behaviors such as accelerating, braking, and changing gears. Similarly, you could have separate objects for the engine, transmission, and wheels, and define relationships between them to model how they work together. In simple words, OOMD is a way of thinking about software design by considering real-world objects and their behaviors, and representing them as software objects that interact with each other.

What is object orientation? Object-Orientation is a programming approach that involves modeling real-world objects as software objects with properties (attributes) and actions (methods). Objects interact with each other, making it easier to design and write more modular, reusable, and maintainable software systems. It's a way of organizing and writing computer programs that makes them easier to understand, maintain, and extend. There are 4 characteristics required by an object oriented approach : ● Identity: Every object in an object-oriented system has a unique identity, which distinguishes it from all other objects. For example, each person has

a unique identity, such as their name, social security number, or passport number. ● Classification: In object-oriented programming, classification refers to the process of grouping objects based on their shared characteristics or attributes. These groups of objects are called classes, and they are defined by a set of properties and behaviors that they share. Let's say we're building a program that represents different vehicles, such as cars, trucks, and motorcycles. Each of these vehicles has a unique set of attributes and behaviors, such as their make, model, and number of wheels. (To implement this in object-oriented programming, we might create a base class called "Vehicle" that defines the shared attributes and behaviors of all vehicles. Then, we can create subclasses for each specific type of vehicle, such as "Car", "Truck", and "Motorcycle". Each subclass would inherit the properties and behaviors defined in the "Vehicle" class, but could also add additional properties and behaviors specific to that type of vehicle. For example, the "Car" subclass might have a number of doors property and a method to start the engine, while the "Truck" subclass might have a cargo capacity property and a method to load and unload cargo. By using classification in this way, we can create a simple and flexible system for representing different types of vehicles in our code.) ● Inheritance: Inheritance is a mechanism that allows new classes to be created by inheriting attributes and behaviors from existing classes. For example, a sports car is a type of car that inherits all the attributes and behaviors of a car, but it also has additional attributes and behaviors, such as a more powerful engine and the ability to reach higher speeds. ● Polymorphism: Polymorphism refers to the ability of objects to exhibit different behavior depending on the context in which they are used. For example, a person can have multiple roles, such as being a student, an employee, and a parent, and they can exhibit different behaviors in each of these roles.

What is object oriented development? Object-oriented development (OOD) is a software development approach that is based on object orientation, a concept that models real-world objects and their behavior as software objects. In OOD, software systems are developed by defining classes that represent objects, and by creating objects that belong to those classes. The classes define the common attributes and behaviors for all objects of that type, and objects inherit those attributes and behaviors from the classes they belong to. OOD involves several steps, including object-oriented analysis (OOA), object-oriented design (OOD), and object-oriented programming (OOP). In OOA, the software system is analyzed to identify the objects and their relationships. In OOD, the objects and their relationships are designed and documented in a class diagram. In OOP, the classes and objects are implemented as code in a programming language. The goal of OOD is to develop software systems that are organized, maintainable, and extensible. By modeling real-world objects and their behavior as software objects, OOD provides a way to capture the complexity of the system and to manage it more effectively. OOD also enables code reuse and makes it easier to add new features and functionality to the system over time. Object oriented methodology Object-oriented methodology is a software development approach that is based on the concept of "objects", which are combinations of data and functions. The approach involves several stages of development, including: ● System conception and analysis: Understanding the requirements and goals of the software project. ● System design: Creating a high-level plan for the software architecture and overall design. ● Class design: Designing the individual objects and their interactions. ● Implementation: Writing the code for the objects and bringing the software to life.

Each stage involves careful consideration of various factors, such as user needs, data structure, and software architecture, to ensure a successful and effective final product.

Object oriented theme The object-oriented theme is a central concept in object-oriented programming (OOP) and refers to the idea of creating software using objects. The main points of this theme are: ● Abstraction: Hiding the implementation details of objects and exposing only the essential features to the rest of the system. ● Encapsulation: Wrapping data and behavior within an object, protecting it from outside interference and misuse. ● Combining data and behavior: Objects in OOP contain both data and the functions that manipulate that data, making the relationship between data and behavior clear and straightforward. ● Sharing: Reusing objects or parts of objects across different parts of a software system to reduce the amount of code that needs to be written and maintained. ● Emphasis on the essence of an object: Focusing on the core characteristics and behavior of an object to define its structure and functionality. ● Synergy: Objects working together to accomplish a task, with each object contributing its unique data and behavior to achieve a common goal. These points are fundamental to OOP and help to make it an effective approach for software development, as they allow for efficient and modular design, flexible and reusable code, and improved maintainability.

Module 2 1. What is object modeling technique? What is the purpose of object modeling technique and what are the phases of object modeling technique? Object modeling technique (OMT) is a software engineering methodology that is typically used in the early-stage of software development to analyze and design the requirements of a system using an object-oriented approach. The purpose of OMT is to create a detailed model of a software system, which can be used to develop, maintain, and modify the system over time. OMT provides a systematic approach to modeling complex systems using object-oriented concepts such as classes, objects, attributes, and relationships. It involves identifying the objects in the system and the relationships between them. OMT diagrams, such as class diagrams and object diagrams, are used to represent the objects and their relationships. Phases of OMT: 1. Analysis: The Analysis phase is the first phase of OMT, and it is focused on understanding the problem domain and requirements of the system. The requirements are then transformed into a conceptual model, which consists of objects, attributes, and relationships. The analysis phase helps to identify the main functionalities of the system and the interactions between its various components. In this phase, the following three models are created: ● Object Model: This model is used to identify the objects in the system and their relationships with each other. The object model is created by analyzing the system requirements and identifying the objects that are needed to fulfill those requirements.

● Dynamic Model: This model is used to describe the behavior of the system and how the objects interact with each other over time. The dynamic model is created by identifying the events that trigger changes in the system and the actions that the objects take in response to those events. It includes sequence diagrams, activity diagrams, and state diagrams that show how objects interact with each other to perform the behaviors of the system. ● Functional Model: This model is used to describe the functions that the system must perform. The functional model is created by identifying the tasks that the system must perform and the objects that are involved in those tasks. 2. System Design: The System Design phase is the second phase of OMT, and it is focused on defining the architecture of the system. In this phase, the conceptual model developed during the analysis phase is refined and transformed into a system design. The system design specifies how the system will be implemented and how its components will interact with each other. This phase involves the identification of subsystems, interfaces, and their interactions. 3. Object Design: The Object Design phase is the third phase of OMT, and it is focused on designing the details of the objects in the system. In this phase, the system design is further refined to focus on the design of individual objects and their interactions. The design of the objects is based on the attributes and behaviors identified during the analysis phase. Object design involves the creation of class diagrams, sequence diagrams, and state transition diagrams. 4. Implementation: The Implementation phase is the fourth and final phase of OMT, and it is focused on actually implementing the system. In this phase, the code is written and tested to ensure that it meets the requirements of the system. The implementation

phase is not represented by a model, but rather by the actual code that is written for the system. The purpose of OMT is to create a detailed model of a software system, which can be used to develop, maintain, and modify the system over time. OMT helps to identify the objects in the system and their relationships, and to define the behavior and functions of the system. This helps to ensure that the system is designed correctly, and that it meets the needs of its users.

The Three Models There are three types of models in the object oriented modeling and designing they are: ● Class Model ● State Model ● Interaction Model 1. Class Model : A Class Model is an object-oriented model used to represent the structure and behavior of a software system. It defines the attributes and behaviors of objects, as well as the relationships between objects. The Class Diagram is the corresponding diagram used to represent the Class Model. In a Class Diagram, classes are represented as rectangles with the class name in the top compartment. The middle compartment lists the attributes (properties) of the class, while the bottom compartment lists the methods (behaviors) of the class. Relationships between classes are represented as lines connecting the classes. There are several types of relationships that can be represented in a Class Diagram, such as inheritance, composition, and association.

Example: Consider a banking system, where we can create a Class Model with classes such as Account, Customer, and Transaction.

● The Account class may have attributes such as account number, balance, and account type, and methods such as deposit and withdrawal. ● The Customer class may have attributes such as name, address, and phone number, and methods such as update contact information. ● The Transaction class may have attributes such as transaction ID, amount, and date, and methods such as record transaction. +----------------+ | Account | +----------------+ | - account_name | | - account_num | | - account_type | | - balance | +----------------+ | + withdraw() | | + deposit() | +----------------+

+----------------+ | Customer | +----------------+ | - name | | - address | | - phone_number| | | | +----------------+ | + update_info()| | | | +----------------+

+----------------+ | Transaction | +----------------+ | - transaction_id| | - date | | - amount | | +----------------+ | + record() | | +----------------+

2. State Model : A State Model is an object-oriented model used to represent the behavior of an object over time. It shows how an object behaves in different states and how it transitions from one state to another. The State Diagram is the corresponding diagram used to represent the State Model. In a State Diagram, the states of an object are represented as circles, with the state name inside the circle. Transitions between states are represented as arrows, with the transition conditions and actions labeled on the arrows. The initial state is represented by a solid black circle, while the final state is represented by a solid black circle with a border.

Example: Consider a simple traffic light system, where we can create a State Model with states such as Red, Green, and Yellow. ● In the Red state, the traffic light displays a red light and stops traffic. ● In the Green state, the traffic light displays a green light and allows traffic to move. ● In the Yellow state, the traffic light displays a yellow light to warn drivers that the light is about to change. 3. Interaction Model : An Interaction Model is an object-oriented model used to represent the interactions between objects in a software system. It shows how objects communicate with each other and how they collaborate to accomplish a task. The following diagrams are used to show the interaction model : ● Use case Diagram: A use case diagram is a high-level diagram that shows the interactions between actors (users or external systems) and the system being modeled. It provides a graphical overview of the system's functionality from a user's perspective. ● Sequence Diagram: Sequence diagrams, on the other hand, show the interactions between objects in a time-ordered manner, depicting(portraying) the messages exchanged between objects and the order in which they occur. ● Activity Diagram: Activity diagrams represent the flow of activities or actions within a system, typically showing the sequence of activities, decision points, and conditional branching.

Module - 3

Class Modeling Class modeling is a technique used in object-oriented programming (OOP) to create a blueprint of the classes that are used to build a software application. In class modeling, a software system is represented as a collection of classes, where each class represents a specific entity or object in the system. The purpose of class modeling is to provide a visual representation of the classes and their relationships, attributes, and behaviors within the system. This allows software developers to better understand the system and its requirements, and to design and implement the system more effectively. Class modeling typically involves the use of Unified Modeling Language (UML) notation to create class diagrams that show the classes, their attributes, methods, and relationships. The class diagram is a type of structural diagram that provides a high-level view of the system's object-oriented design. Overall, class modeling is an important step in the software development process that helps ensure that the resulting software system is well-structured, maintainable, and meets the requirements of its users. Object and Class Concept : In class modeling, an object is an instance of a class that has its own state and behavior. It can be thought of as a real-world object with its own identity, that describes it from other objects in a system; state, that determines the properties of an object as well as the values of the properties that the object holds; and behavior, that represents externally visible activities performed by an object in terms of changes in its state. For example, a car is an object that has properties such as make, model, and year, and actions such as accelerating, braking, and turning. A class, on the other hand, is a blueprint or template for creating objects. It defines the properties and behaviors that objects of that class will have. For

example, a Car class might have properties such as make, model, and year, and methods such as accelerate, brake, and turn. The concepts of objects and classes are fundamental to object-oriented programming, and are used to create complex systems that are easier to manage and maintain. By breaking down a system into classes and objects, developers can create code that is modular, reusable, and easier to test and debug.

Link and Association Concept : Link: ● A link is a physical or conceptual connection among instances of classes i.e. objects. ● a link is considered as an instance of an association. ● It is represented by a line connecting two objects in a class diagram. ● A link does not provide any additional information about the relationship beyond the fact that there is a connection between the objects. Association: ● An association is a relationship between two or more classes or objects. ● an association is a group of links that relates objects from the same classes. ● It is a specification about the collection of links. ● It represents a connection between two class types. ● It is represented by a line with additional properties such as multiplicities, roles, navigability, etc., in a class diagram. ● An association provides additional information about the nature of the relationship, such as the number of instances involved in the relationship, the roles played by the instances, and whether the relationship is navigable in one or both directions. ● Associations can be either unidirectional or bidirectional, meaning that they can be traversed in one direction or both directions respectively.

To summarize, a link represents a connection between two instances of classes, while an association represents a connection between two class types and provides additional information about the nature of the relationship.

Cardinality Ratio of Association Cardinality ratio of an association is the way of expressing the number of instances of one class that are related to the number of instances of another class through the association. Cardinality ratio is usually represented as a pair of numbers separated by a colon (:), with the first number representing the minimum number of instances and the second number representing the maximum number of instances. Here are some examples: 1. One-to-One (1:1): each instance of one class is related to exactly one instance of the other class, and vice versa. 2. One-to-Many (1:N): each instance of one class is related to zero or more instances of the other class, while each instance of the other class is related to exactly one instance of the first class. 3. Many-to-One (N:1): each instance of one class is related to exactly one instance of the other class, while each instance of the other class is related to zero or more instances of the first class. 4. Many-to-Many (N:M): each instance of one class is related to zero or more instances of the other class, while each instance of the other class is related to zero or more instances of the first class. Cardinality ratio provides information about the number of instances involved in an association and helps to define the constraints of the relationship between classes. It is often included in a class diagram as a notation on the association line.

UML

UML (Unified Modeling Language) is a standardized visual modeling language used to represent software systems. It was created by the Object Management Group (OMG) to provide a common language for software development. One of the benefits of using UML is that it can be used to generate code in various programming languages. While UML is not a programming language itself, the diagrams and models created using UML can be used as a blueprint to generate code in languages such as Java, C++, and Python. UML is not a programming language, but rather a set of tools and diagrams that can be used to model software systems. UML diagrams can be used to represent various aspects of a software system, including its structure, behavior, and interactions with other systems. Some of the most commonly used UML diagrams include: ● Class diagrams, which represent the structure of a system by showing its classes, attributes, and relationships. ● Use case diagrams, which represent the interactions between a system and its users. ● Activity diagrams, which represent the flow of control within a system. ● Sequence diagrams, which represent the interactions between objects in a system over time. ● State machine diagrams, which represent the behavior of objects in a system as they transition between different states. Overall, UML provides a standardized and widely recognized language for software developers and stakeholders to communicate and collaborate on the design and documentation of software systems.

Class Diagram : A class diagram is a type of UML (Unified Modeling Language) diagram. A class diagram is a visual representation of the classes and their relationships in a software system. It shows the attributes and behaviors of the classes, as well as the connections between them. It's a way to understand the structure of the system and how different components are related to each other.

In a Class Diagram, classes are represented as rectangles with the class name in the top compartment. The middle compartment lists the attributes (properties) of the class, while the bottom compartment lists the methods (behaviors) of the class. Relationships between classes are represented as lines connecting the classes. There are several types of relationships that can be represented in a Class Diagram, such as inheritance, composition, and association.

Benefits of class diagram some key benefits of using a class diagram: ● Provides a visual representation of the system's architecture and structure. ● Helps to identify the relationships between different classes and components. ● Aids in communication and understanding of the system's design and functionality. ● Improves reusability by identifying common patterns and components that can be reused in future projects. ● Provides a blueprint for development efforts, guiding the planning and design phases of a project. ● Helps in testing and maintenance by identifying the components that need to be tested and modified. ● Aids in scalability by providing a clear understanding of the system's structure and relationships between components. Elements of Class Diagram ● Class Name The name of the class is only needed in the graphical representation of the class. It appears on the top most compartment. A class name should always start with a capital letter. A class name should always be in the center of the first compartment. ● Attributes An attribute is a named property of a class that describes the value holded by each object of the class. A value is a piece of data.

● Operations An operation is a function or procedure that may be applied to or by objects in a class.

Object Diagram :

An object diagram is a structural diagram in UML (Unified Modeling Language) that depicts a set of objects and their relationships at a specific point in time. It shows how objects interact with each other within a system or application, and can be used to illustrate a particular scenario or use case. An object diagram consists of objects (instances of classes), which are represented as rectangles with the object name and class name separated by a colon. The objects are connected with lines to show the relationships between them. The lines may have labels indicating the type of relationship, such as association, aggregation, composition, or inheritance. Object diagrams are useful for visualizing and communicating the structure of a system, especially when dealing with complex object-oriented systems. They can help identify potential design flaws or inconsistencies, and can aid in the testing and debugging process. They are often used in conjunction with other UML diagrams, such as class diagrams and sequence diagrams, to provide a more complete view of the system.

Inheritance

Inheritance is a fundamental concept in object-oriented programming that allows a new class to be based on an existing class, inheriting its attributes and behaviors. It promotes code reuse and creates a hierarchical structure of classes with increasing levels of specialization. Inheritance is implemented using keywords such as "extends" in Java and ":" in Python. There are several types of inheritance in OOP, including:

1. Single inheritance - one subclass inherits from one superclass 2. Multiple inheritance - one subclass inherits from multiple superclasses 3. Multilevel inheritance - a subclass inherits from a superclass, which in turn inherits from another superclass 4. Hierarchical inheritance - multiple subclasses inherit from the same superclass. 5. Hybrid Inheritance - A combination of multiple and multilevel inheritance is known as hybrid inheritance.

Inheritance simplifies code, promotes efficiency, and enhances modularity and scalability. It is an essential concept for developers working with object-oriented programming languages.

@Generalization

Generalization is a fundamental concept in object-oriented programming (OOP) that allows developers to model real-world concepts and relationships between them. In object modeling, generalization refers to the process of creating a new class from an existing class or classes, inheriting the attributes and behaviors of the parent class(es) and adding additional attributes and behaviors specific to the new class. Generalization is often used to represent hierarchies of classes, with more general or abstract classes at the top of the hierarchy and more specific or concrete classes at the bottom. This is known as an inheritance hierarchy or an "is-a" relationship. For example, a "Vehicle" class might be a parent class to more specific classes like "Car," "Truck," and "Motorcycle." By using generalization in object modeling, developers can reduce code duplication, increase code reuse, and create more flexible and modular code structures. It also allows developers to create more expressive and meaningful class hierarchies that accurately represent the real-world relationships between objects.

@Aggregation Aggregation is a relationship between objects in object-oriented modeling where one object contains or is composed of other objects. It represents a "has-a" relationship where an object of one class has one or more objects of another class as its part.

In aggregation, the contained objects can exist independently of the container object, which means that they can be shared between multiple container objects. Aggregation is often used to represent the concept of a "part-whole" relationship between objects, where the container object is the whole and the contained objects are its parts. For example, consider a car object that contains four wheel objects. The car object is the container object, and the wheel objects are the contained objects. The aggregation relationship between them can be represented as follows: +-------+ +---------+ | Car |--| Wheel | +-------+ +---------+ In this example, a car has four wheels, but the wheels can exist independently of the car. Aggregation is represented in UML (Unified Modeling Language) using a diamond-shaped arrowhead from the container class to the contained class. The diamond indicates that the container class aggregates the contained class. Aggregation is different from composition, which is a stronger form of aggregation where the contained object is a part of the container object and cannot exist independently.

Abstract Class

An abstract class is a class that cannot be instantiated, meaning you cannot create an object directly from an abstract class. Instead, you can only create objects from its concrete subclasses. Abstract classes are used to define a common interface for a group of related classes. It defines the common attributes and methods that the subclasses will inherit and share. An abstract class is defined using the "abstract" keyword in the class declaration. An abstract class can have both abstract and non-abstract methods. An abstract method is a method that is declared but not defined, meaning it has no implementation in the abstract class. Instead, the implementation is provided by its concrete subclasses.

Multiple Inheritance Multiple inheritance is a feature in some object-oriented programming languages that allows a class to inherit from more than one base class. In multiple inheritance, a class can inherit attributes and methods from multiple parent classes, and it can also define its own attributes and methods. For example, in a scenario where a class "Student" inherits from two parent classes "Person" and "Scholarship", the "Student" class would have access to attributes and methods defined in both parent classes. This allows for more flexible and modular class design, as different classes with different functionalities can be combined to create a more complex class.

#Meta Data Metadata is data that describes other data. In other words, it provides information about a particular set of data, such as its format, content, structure, or context. Metadata is used to help manage and organize large amounts of data and make it easier to search, access, and use. …

#Constraints In object-oriented modeling, constraints refer to the rules and requirements that must be satisfied by the system being modeled. Constraints can be used to ensure that the system behaves correctly and meets the desired specifications. There are several types of constraints in object-oriented modeling, including: 1. Structural constraints: These constraints define the relationships between objects in the system, such as inheritance relationships between classes or association relationships between objects. 2. Behavioral constraints: These constraints define the rules that govern the behavior of the system, such as the order of method calls or the allowed values for object attributes. 3. Semantic constraints: These constraints define the meaning and interpretation of the data in the system, such as the units of measurement or the allowed values for certain fields. 4. Integrity constraints: These constraints define the rules that ensure the consistency and accuracy of the data in the system, such as constraints on primary and foreign keys in a database. Constraints can be represented in object-oriented modeling using various techniques, such as UML diagrams or formal modeling languages like Object Constraint Language (OCL). By incorporating constraints into the modeling process, developers can ensure that the resulting system meets the desired specifications and behaves correctly. Constraints on Objects Constraints on objects refer to the rules and requirements that must be satisfied by the objects in an object-oriented system. These constraints are used to ensure that the objects behave correctly and meet the desired specifications.

There are several types of constraints that can be applied to objects, including: 1. Attribute constraints: These constraints define the rules that govern the values that can be assigned to an object's attributes. For example, an object representing a person's age may have an attribute constraint that requires the age to be a positive integer. 2. Relationship constraints: These constraints define the rules that govern the relationships between objects. For example, an object representing a book may have a relationship constraint that requires it to be associated with one or more objects representing authors. 3. Behavior constraints: These constraints define the rules that govern the behavior of objects. For example, an object representing a bank account may have a behavior constraint that requires the balance to be updated whenever a deposit or withdrawal is made. 4. Integrity constraints: These constraints define the rules that ensure the consistency and accuracy of the data in the system. For example, an object representing a database record may have an integrity constraint that requires a certain field to be unique. Constraints on objects can be represented in object-oriented modeling using various techniques, such as UML diagrams or formal modeling languages like Object Constraint Language (OCL). By incorporating constraints into the modeling process, developers can ensure that the resulting system meets the desired specifications and behaves correctly. Constraints on Generalization Sets Constraints on generalization sets are used to specify additional rules or requirements that must be satisfied by the objects in the set. A generalization set is a grouping of related classes in a class hierarchy, where the classes share common characteristics and can be treated as a group. Constraints on generalization sets can be used to ensure that the objects in the set behave correctly and meet the desired specifications.

There are several types of constraints that can be applied to generalization sets, including: 1. Cardinality constraints: These constraints specify the number of objects that can be included in the generalization set. For example, a generalization set representing different types of vehicles may have a cardinality constraint that requires at least one object representing a car or a truck. 2. Disjointness constraints: These constraints specify whether the objects in the generalization set can overlap with objects in other generalization sets. For example, a generalization set representing different types of animals may have a disjointness constraint that requires the objects to be either mammals or reptiles, but not both. 3. Completeness constraints: These constraints specify whether all possible objects that can be modeled by the generalization set are included in the set. For example, a generalization set representing different types of vehicles may have a completeness constraint that requires all objects to be either cars or trucks, with no other types of vehicles allowed. Constraints on generalization sets can be represented in object-oriented modeling using various techniques, such as UML diagrams or formal modeling languages like Object Constraint Language (OCL). By incorporating constraints into the modeling process, developers can ensure that the resulting system meets the desired specifications and behaves correctly.

Module - 4

State Modeling

In the context of object-oriented programming (OOP), state modeling is a technique used to represent the different states that an object can be in during its lifecycle. It involves defining a set of attributes that describe the state of the object, and a set of operations that can be performed on the object to change its state. In OOP, an object is an instance of a class, which is a blueprint that defines the attributes and behaviors of objects of that type. State modeling is used to define the attributes that describe the state of an object, and the behaviors that can be performed on that object to change its state. For example, let's say we have a class called "Car" that represents a car object. The state of a car object can be described by attributes such as its speed, fuel level, and gear. The behaviors that can be performed on the car object to change its state might include accelerating, braking, and shifting gears. By modeling the different states of an object and the transitions between those states, we can better understand how the object behaves and can design more effective and efficient software systems. State modeling is a powerful tool for designing complex software systems, especially those that involve many objects and interactions between those objects.

Event In state modeling, an event is a trigger that causes a transition between two states in a state machine. Events represent external stimuli or inputs that can change the state of the system being modeled. They are typically represented as arrows connecting states in a state machine diagram. For example, consider a vending machine that dispenses beverages. The vending machine can be modeled as a state machine, with states such as "idle", "waiting for payment", "dispensing", and "out of order". An event in this context might be a user inserting coins into the machine to make a payment, or selecting a beverage from the available options.

When an event occurs, it triggers a transition from one state to another in the state machine. For example, if a user inserts coins into the vending machine, it might transition from the "waiting for payment" state to the "dispensing" state, where it dispenses the selected beverage. Events can also have associated conditions or actions that are executed when the event occurs. For example, in the vending machine example, an event might have a condition that checks whether the user has inserted enough coins to make a payment, and an action that deducts the payment from the user's account. Overall, events play a critical role in state modeling, as they represent the external inputs that drive state transitions and enable the system to respond to changes in its environment or user interactions. Types of events : (nicely explained in college notebook)

States In state modeling, a state represents a condition or mode of a system at a particular point in time. It is a snapshot of the system's behavior, describing the values of its variables, attributes, or properties at a given moment. States are often depicted as nodes or circles in a state diagram or state machine. For example, consider a traffic light system at an intersection. The traffic light system can be modeled as a state machine, with states such as "green", "yellow", and "red", representing the different states of the traffic lights. At any given time, the traffic light system is in one of these states, and the state determines the behavior of the traffic lights, such as which lights are illuminated and for how long. States can also have associated actions or behaviors that are performed when the system enters or exits the state. For example, when the traffic light system transitions from the "green" state to the "yellow" state, it might activate a warning signal to alert drivers to prepare to stop.

Overall, states play a fundamental role in state modeling, as they enable us to represent the different modes or conditions of a system and how it behaves under different circumstances. By defining states and the transitions between them, we can create a model of a system that accurately reflects its behavior and can be used to analyze, design, and simulate the system's behavior under different scenarios. State Diagram A state diagram is a graphical representation of a state machine or finite automaton that shows the different states that a system can be in and the transitions between those states. State diagrams are commonly used in state modeling, which is a technique used to model the behavior of systems that change state in response to events or inputs. In a state diagram, states are represented as nodes or circles, and transitions between states are represented as directed edges or arrows. Each transition represents a possible change in the state of the system in response to an event or input. Transitions may have labels that specify the event or input that triggers the transition, as well as any conditions or actions that must be met or performed in order for the transition to occur. For example, consider a simple vending machine that accepts coins and dispenses candy. The state diagram for the vending machine might have states such as "idle", "waiting for payment", "dispensing", and "out of order", and transitions between these states that are triggered by events such as "coin inserted" or "candy dispensed". State diagrams can be used to model the behavior of a wide variety of systems, from simple machines like vending machines to complex software systems with many interacting components. They are a powerful tool for visualizing and understanding the behavior of systems, and can help to identify potential errors, inefficiencies, or improvements in the design of a system.

Parts of states

A state model represents the behavior of a system as a sequence of states, where each state corresponds to a specific condition or situation in the system. A state consists of a set of attributes that describe the system's behavior, characteristics, and values at a particular point in time. The parts of a state in a state model can vary depending on the specific system being modeled, but typically include: ● State name: A unique identifier for the state that is easy to understand and remember. ● Attributes: The set of variables or properties that describe the state of the system, such as temperature, pressure, velocity, etc. ● Events: The actions or stimuli that cause the system to transition from one state to another, such as user input, sensor readings, or time-based triggers. ● Actions: The operations or behaviors that are performed when a system transitions to a particular state, such as sending a notification, updating a database, or changing a physical setting. ● Guards: The conditions or constraints that must be met in order for a transition to occur, such as certain inputs or states being present or absent, or specific values being within a certain range. ● Transitions: The pathways that connect states, indicating the conditions and events that trigger a change in the system's behavior. Transitions are often represented as arrows between states in a state diagram or flowchart. Together, these parts of a state help to create a clear and comprehensive model of a system's behavior, allowing designers, developers, and other stakeholders to better understand how the system operates and how it can be improved or optimized.

Module - 5 A use case diagram is a type of UML (Unified Modeling Language) diagram that describes the behavior of a system or application from the point of view of its users. It consists of several components, including: Actors: Actors are the external users, systems, or entities that interact with the system being modeled. Actors are represented by stick figures and are usually located on the left side of the diagram. Use cases: Use cases are the actions or tasks that a user or actor can perform within the system. Use cases are represented by ovals and are usually located on the right side of the diagram. Relationships: Relationships are the connections between actors and use cases. There are several types of relationships that can be used in a use case diagram, including: ● Association: An association is a simple relationship between an actor and a use case. It shows that the actor is involved in the use case. ● Extend: An extend relationship indicates that a use case can be extended to include additional functionality.

● Include: An include relationship indicates that a use case includes another use case as a part of its behavior.

System boundary: The system boundary is a rectangle that encloses all the actors and use cases that are part of the system being modeled. It represents the boundaries of the system and the interactions that take place within it. # symbols used in use case diagrams are important to remember. See in the college pdf notes. #

College Registration system use case diagram:

SEQUENCE MODEL

In object-oriented modeling and designing, a sequence model is a type of diagram that illustrates the interactions between different objects or components in a system. It shows the order of events or messages exchanged between the objects or components, and how they collaborate to achieve a specific task or behavior. A sequence model can be used to model and analyze the behavior of a system, and facilitate communication and collaboration between developers and stakeholders. In a sequence model, objects are represented as lifelines, which are vertical lines that show the lifespan of an object during the sequence. Messages between objects are represented by arrows, and the order of messages is indicated by their position along the lifelines.

Sequence models can be used in different stages of the software development life cycle, such as during requirements analysis, design, implementation, and testing. They can also be used to document and communicate the behavior of an existing system, and to help identify opportunities for improvement or optimization. Overall, sequence models are an important tool in object-oriented modeling and designing, as they provide a visual representation of the interactions between different objects or components in a system, and help to identify potential issues or inefficiencies in the system's design.

SCENARIO :

A scenario in sequence modeling refers to a specific sequence of events or actions that occur in a system or process. It describes how different objects or components interact with each other to accomplish a particular task or achieve a specific goal. In essence, a scenario outlines a story of how a system or process behaves in response to certain events or actions. A scenario is an essential part of sequence modeling as it helps to capture the dynamic behavior of the system or process being modeled. It serves as a blueprint for developing sequence diagrams, which illustrate the interactions between objects or components in a system over time. By modeling different scenarios, designers can identify potential problems or inefficiencies in a system and develop solutions to address them.

Here's a simple example of a scenario in sequence modeling: Let's say we're modeling a simple online ordering system for a pizza restaurant. One scenario we might consider is the "Place Order" scenario. It could involve the following steps: 1. The customer selects the desired pizza and adds it to their order.

2. The customer enters their delivery address and payment information. 3. The system verifies the payment and delivery information and displays a confirmation message to the customer. 4. The system sends the order to the restaurant's kitchen for preparation. 5. The system updates the customer's order status to "Preparing" and displays an estimated delivery time. 6. The delivery driver is notified of the order and begins the delivery process. 7. The system updates the customer's order status to "Out for Delivery." 8. The driver delivers the pizza to the customer and marks the order as complete. This scenario outlines a specific sequence of events that must occur in the system for a customer to successfully place an order and receive their pizza. By modeling this scenario, we can identify any potential issues or bottlenecks in the ordering process and optimize the system accordingly.

SEQUENCE DIAGRAM : A sequence diagram is a type of UML (Unified Modeling Language) diagram used in software engineering and system design. It represents the interactions between objects or components in a system over time. A sequence diagram shows the messages exchanged between different objects or components in a system, along with the sequence in which they occur. The vertical axis represents time, with messages sent from top to bottom. The horizontal axis represents the different objects or components involved in the interaction. A sequence diagram typically consists of lifelines, which represent the different objects or components in the system, and messages, which represent the interactions between those objects or components.

Messages can be synchronous or asynchronous, and can have parameters and return values. Sequence diagrams are useful for visualizing the dynamic behavior of a system and for identifying potential issues or inefficiencies in the system's design. They can be used to model different scenarios and to communicate the system's behavior to stakeholders and other members of the development team.

BENEFITS OF SEQUENCE DIAGRAM : 1. Visualize system behavior: Sequence diagrams provide a visual representation of the interactions between objects or components in a system over time. This allows designers and developers to better understand the system's behavior and to identify potential issues or inefficiencies. 2. Improve system design: By modeling different scenarios using sequence diagrams, designers can refine and optimize the system's design to improve performance, reliability, and scalability. 3. Communicate system behavior: Sequence diagrams are a powerful tool for communicating the system's behavior to stakeholders, including business analysts, project managers, and developers. They can help ensure that everyone involved in the project has a clear understanding of how the system works. 4. Aid in testing and debugging: Sequence diagrams can be used to identify potential issues or bugs in the system's design before it is implemented. They can also be used to aid in testing and debugging by providing a clear understanding of the system's behavior and expected outcomes. 5. Facilitate collaboration: Sequence diagrams can be used to facilitate collaboration between different members of the development team. They can help ensure that everyone is on the same page when it

comes to the system's behavior and can help identify areas where further collaboration is needed. Overall, sequence diagrams are a valuable tool for software engineering and system design, and can help ensure that systems are designed and developed in a clear and efficient manner.

ACTIVITY MODEL

An activity model is a representation or a description of a process, system or workflow that shows how different activities are connected and how information flows between them. It is typically used to understand and analyze complex systems, identify areas for improvement, and make changes to optimize efficiency and effectiveness. Activity models can take many forms, such as flowcharts, diagrams, process maps, or any other visual representation that clearly depicts the activities involved in a process or system. They can also include information such as inputs, outputs, resources, and decision points, depending on the level of detail required. Activity models are used in a variety of fields, including business, engineering, software development, and project management. They can be created using various tools, such as Microsoft Visio, BPMN (Business Process Model and Notation), UML (Unified Modeling Language), or other specialized software.

Data Flow Diagram

Levels in Data Flow Diagrams (DFD) In Software engineering DFD(data flow diagram) can be drawn to represent the system of different levels of abstraction. Higher-level DFDs are partitioned into low levels-hacking more information and functional elements. Levels in DFD are numbered 0, 1, 2 or beyond. Here, we will see mainly 3 levels in the data flow diagram, which are: 0-level DFD, 1-level DFD, and 2-level DFD. 0-level DFD: It is also known as a context diagram. It’s designed to be an abstraction view, showing the system as a single process with its relationship to external entities. It represents the entire system as a single bubble with input and output data indicated by incoming/outgoing arrows.

1-level DFD: In 1-level DFD, the context diagram is decomposed into multiple bubbles/processes. In this level, we highlight the main functions of the system and breakdown the high-level process of 0-level DFD into subprocesses.

2-level DFD: 2-level DFD goes one step deeper into parts of 1-level DFD. It can be used to plan or record the specific/necessary detail about the system’s functioning.

Module - 6

Development Stages in Object Orientation In object-oriented modeling and designing, the development process can be broadly divided into the following stages: 1. System Conception: This is the initial stage where the idea for the system is conceived. At this stage, the goals and objectives of the system are defined, and a feasibility study is conducted to determine if the system is viable. 2. Analysis: This stage involves gathering and analyzing requirements for the system. Requirements are typically gathered from stakeholders and end-users of the system. The analysis phase aims to identify the objects, classes, and relationships that will form the system's architecture. 3. System Design: In this stage, the high-level system architecture is designed. The system design includes the overall structure and behavior of the system, as well as the various subsystems and modules that will make up the system. 4. Class Design: In this stage, the detailed design of each class is created. The class design includes defining the attributes, methods, and relationships of each class. The design is typically represented using UML class diagrams. 5. Implementation: This stage involves writing code based on the design specifications. The code is organized into classes and objects based on the design. Object-oriented programming languages such as Java, C++, and Python are commonly used for implementation.

6. Testing: In this stage, the system is tested to ensure that it meets the requirements and functions as expected. Testing can be done at various levels, including unit testing, integration testing, and system testing. 7. Training: Once the system is developed, end-users and stakeholders need to be trained on how to use it. This stage involves developing user manuals, training materials, and conducting training sessions. 8. Deployment: This stage involves deploying the system in the production environment. The system is installed, configured, and made available to end-users. This stage also involves creating a maintenance plan and providing ongoing support. 9. Management: After deployment, the system needs to be managed and maintained. This stage involves monitoring the system, fixing bugs, making updates, and enhancing the system to meet changing user requirements. Throughout these stages, object-oriented design principles such as encapsulation, inheritance, and polymorphism are applied to create a system that is modular, maintainable, and scalable. Additionally, design patterns can be used to solve common design problems and improve the overall design of the system.

Development Lifecycle Requirements gathering | v System Analysis | v System Design | v Detailed Design |

v Implementation | v Testing | v Deployment | v Maintenance The development life cycle in object-oriented modeling and designing is a series of steps that are followed to design, develop, and deploy software systems using object-oriented principles. The typical development life cycle for object-oriented systems includes the following stages: 1. Requirements gathering and analysis: In this stage, the requirements for the system are gathered and analyzed. This involves understanding the needs of the stakeholders and identifying the objects, classes, and relationships that will form the system's architecture. 2. System design: In this stage, the high-level system architecture is designed. The system design includes the overall structure and behavior of the system, as well as the various subsystems and modules that will make up the system. 3. Detailed design: In this stage, the detailed design of each class is created. The class design includes defining the attributes, methods, and relationships of each class. The design is typically represented using UML class diagrams. 4. Implementation: In this stage, the code is written based on the design specifications. The code is organized into classes and objects based on the design. Object-oriented programming languages such as Java, C++, and Python are commonly used for implementation.

5. Testing: In this stage, the system is tested to ensure that it meets the requirements and functions as expected. Testing can be done at various levels, including unit testing, integration testing, and system testing. 6. Deployment: In this stage, the system is deployed in the production environment. The system is installed, configured, and made available to end-users. This stage also involves creating a maintenance plan and providing ongoing support. 7. Maintenance: After deployment, the system needs to be managed and maintained. This stage involves monitoring the system, fixing bugs, making updates, and enhancing the system to meet changing user requirements. Throughout these stages, object-oriented design principles such as encapsulation, inheritance, and polymorphism are applied to create a system that is modular, maintainable, and scalable. Additionally, design patterns can be used to solve common design problems and improve the overall design of the system. The development life cycle is iterative, and each stage may involve revisiting previous stages to make adjustments based on feedback and new requirements.

Module - 7

Overview of System Design System design in object-oriented modeling and designing involves defining the overall architecture, structure, and behavior of a software system using object-oriented concepts such as classes, objects, inheritance, polymorphism, and encapsulation.

During system design, the software requirements are translated into a high-level design specification that outlines how the various components of the system will work together. This typically involves identifying the classes and objects that will be needed, defining their attributes and behaviors, and determining how they will interact with each other to achieve the desired functionality. The following points are considered to design a system efficiently: 1. Breaking a system into subsystems Breaking a system into subsystems in system design is a process of dividing a large and complex system into smaller and more manageable parts, each of which can be developed, tested, and maintained independently. A subsystem is a self-contained module of a larger system that performs a specific set of functions or services. Breaking a system into subsystems has several benefits. It makes the system easier to understand, design, and implement, as the complexity is reduced by dividing the system into smaller, more manageable pieces. It also allows for greater flexibility, as each subsystem can be developed and tested independently, making it easier to add new features or modify existing ones. In system design, the process of breaking a system into subsystems typically involves identifying the functional requirements of the system and grouping them into related sets of functions. Each set of functions is then allocated to a subsystem that is responsible for providing those functions. The subsystems are designed to interact with each other through well-defined interfaces, ensuring that they work together seamlessly. For example, in a software application, a system may be broken down into subsystems such as the user interface, the database subsystem, the communication subsystem, and the processing subsystem. Each of these subsystems may be developed by a separate team of developers, each with their own set of requirements and constraints, but they must all work together to provide the functionality of the system as a whole. Overall, breaking a system into subsystems in system design is an important step in creating a well-designed, modular, and scalable system. It allows for

greater flexibility, ease of maintenance, and improved performance, and can make the system easier to understand and use. 2. Identity Concurrency In the context of system design, identifying concurrency refers to the process of identifying areas of a system where multiple tasks or processes can be executed simultaneously or in parallel. Concurrency is an important aspect of system design because it can significantly improve the performance, scalability, and responsiveness of a system. Concurrency can be achieved through various techniques, such as multithreading, multiprocessing, and distributed processing. Multithreading involves dividing a single process into multiple threads of execution that can run concurrently, while multiprocessing involves running multiple processes in parallel on different processors or cores. Distributed processing involves distributing tasks across multiple computers or nodes in a network to achieve parallelism. Identifying concurrency in a system typically involves analyzing the tasks and processes that the system must perform and identifying those that can be executed concurrently. For example, in a web application, multiple users may be accessing the system simultaneously, so concurrency can be achieved by processing each user's request in a separate thread or process. Concurrency can also be used to improve the performance of resource-intensive tasks, such as data processing or image rendering. By dividing these tasks into smaller subtasks that can be executed in parallel, the overall time required to complete the task can be reduced, resulting in improved performance and responsiveness. Overall, identifying concurrency in system design is an important step in creating a high-performance and scalable system. By analyzing the system requirements and identifying areas where concurrency can be used, designers can ensure that the system can handle large volumes of data and multiple users without sacrificing performance or responsiveness.

3. Allocation of Subsystems In system design, allocation of subsystems refers to the process of assigning different functions or tasks to different subsystems that will work together to achieve the overall system objective. This involves breaking down the system into smaller parts or subsystems, identifying their specific functions, and allocating the resources required to fulfill those functions. The allocation of subsystems is an important step in system design because it helps to ensure that the system is optimized for its intended purpose. By breaking the system down into smaller parts, designers can focus on specific aspects of the system and ensure that each subsystem is designed to perform its function efficiently and effectively. The allocation of subsystems involves several steps, including: ● ● ● ●

Defining the overall system requirements and objectives Identifying the different subsystems required to achieve those objectives Defining the functions of each subsystem Allocating resources, such as hardware, software, and personnel, to each subsystem ● Ensuring that each subsystem is designed and integrated to work together with the other subsystems to achieve the overall system objective. Effective allocation of subsystems is essential to ensure that the system functions as intended and meets the needs of its users. It helps to ensure that the system is reliable, efficient, and cost-effective, and that it can be easily maintained and upgraded over time. 4. Management of data storage The management of data storage in system designing refers to the process of determining the storage requirements of a system and designing an efficient and effective storage solution that can meet those requirements. This involves analyzing the types and amounts of data that the system will generate and/or process, and determining how that data will be stored, accessed, and managed.

There are several factors that need to be considered when managing data storage in system design, including: ● Data volume and velocity: The amount of data that the system generates and the rate at which it is generated. ● Data structure: The way data is organized and structured, including its format, schema, and metadata. ● Access patterns: The frequency and manner in which the data will be accessed, including read and write operations. ● Security and compliance: The need to protect sensitive data, comply with relevant regulations, and ensure data privacy. ● Scalability: The ability to expand storage capacity as the system grows and more data is generated. To manage data storage effectively, system designers must choose an appropriate storage architecture, such as file-based storage, database storage, object-based storage, or cloud-based storage. They must also determine the most appropriate storage media, such as hard disk drives, solid-state drives, tape drives, or cloud storage services. Additionally, system designers must consider data backup and recovery strategies to ensure that data is not lost in case of system failures, disasters, or cyber-attacks. This involves creating data backups and replication schemes, and designing data recovery procedures. Overall, effective management of data storage is crucial for system designers to ensure that the system can handle large volumes of data efficiently, securely, and reliably, while meeting the performance, availability, and scalability requirements of its users.

5. Handling Global Resources

Handling global resources in system designing refers to the process of managing resources that are shared across different components or subsystems of a system. These resources may include hardware resources such as memory, network bandwidth, and processing power, as well as software resources such as libraries, modules, and databases. Global resources are often critical to the performance and availability of a system, and therefore, they must be managed effectively to ensure optimal system performance. Some of the key considerations for handling global resources in system design include: ● Resource allocation: This involves determining how much of a resource is required by each component or subsystem of the system and allocating resources accordingly. ● Resource sharing: This involves ensuring that resources are shared effectively among different components or subsystems of the system. This may involve implementing resource sharing protocols or techniques such as caching, load balancing, and distributed computing. ● Resource optimization: This involves optimizing the use of global resources to minimize waste and maximize efficiency. This may involve techniques such as resource pooling, dynamic resource allocation, and auto-scaling. ● Resource monitoring: This involves monitoring the usage and performance of global resources to detect and address performance bottlenecks or issues. This may involve implementing monitoring tools or techniques such as performance metrics, logging, and tracing. ● Resource management: This involves managing the lifecycle of global resources, including their creation, modification, and destruction. This may involve implementing resource management processes or techniques such as resource tagging, resource recycling, and resource retirement. Overall, effective handling of global resources is essential for system designers to ensure that the system can meet its performance, availability, and scalability

requirements while minimizing resource waste and maximizing resource utilization.

6. Choosing a software control strategy Choosing a software control strategy in system design refers to the process of selecting the appropriate software control mechanisms and algorithms to manage the behavior and performance of the system. This involves identifying the system's control requirements and selecting the most effective control strategy to achieve the desired system behavior. There are various software control strategies that can be used in system design, including: Proportional-Integral-Derivative (PID) Control: This is a common feedback control technique that adjusts the system's behavior by analyzing the difference between the desired output and the actual output of the system. Model Predictive Control (MPC): This is a control strategy that uses a predictive model of the system to optimize the system's behavior by anticipating future behavior. Fuzzy Logic Control: This is a control strategy that uses fuzzy logic rules to manage the system's behavior based on a set of linguistic rules. State Space Control: This is a control strategy that represents the system's behavior using a set of state variables, and adjusts the system's behavior based on the current state of the system. Artificial Intelligence-based Control: This is a control strategy that uses machine learning techniques, such as neural networks or decision trees, to optimize the system's behavior based on past behavior and expected future behavior. Choosing the appropriate software control strategy involves considering the system's requirements, constraints, and expected performance. The system

designer must also consider the complexity and feasibility of implementing the chosen control strategy within the system's hardware and software architecture. Overall, selecting an appropriate software control strategy is essential for system designers to ensure that the system can achieve the desired behavior, performance, and efficiency, while maintaining stability and reliability.

7. Handling Boundary Conditions Handling boundary conditions in system designing refers to the process of identifying and managing the constraints and limitations that arise at the interfaces between different components or subsystems of a system, or between the system and its external environment. Boundary conditions may include physical, logical, or operational constraints that affect the behavior or performance of the system. Examples of boundary conditions in system design may include limitations on memory, bandwidth, latency, or input/output data rates, as well as constraints on data formats, protocols, or communication channels. Some of the key considerations for handling boundary conditions in system design include: Boundary Identification: This involves identifying the boundaries between different components or subsystems of the system, or between the system and its external environment. Boundary Analysis: This involves analyzing the constraints and limitations that arise at each boundary, and determining the impact of these boundary conditions on the behavior and performance of the system. Boundary Management: This involves managing the boundary conditions to ensure that they are handled effectively by the system. This may involve implementing protocols or techniques such as buffering, error handling, or data compression.

Boundary Testing: This involves testing the system's ability to handle boundary conditions, and verifying that the system behaves correctly and reliably under different boundary conditions. Boundary Optimization: This involves optimizing the system's behavior and performance under different boundary conditions, and identifying ways to minimize the impact of boundary conditions on system performance. Overall, effective handling of boundary conditions is essential for system designers to ensure that the system can operate efficiently and reliably under different operating conditions and constraints. By identifying and managing boundary conditions effectively, system designers can improve the overall performance, stability, and reliability of the system.

8. Setting Trade off priorities Setting trade-off priorities means making decisions about what is most important or valuable in a situation where there are limited resources or conflicting goals. It involves determining which goals or objectives should be prioritized over others, and accepting that in some cases, achieving one goal may come at the expense of another. Trade-off priorities can be based on factors such as cost, time, quality, risk, or the preferences and needs of stakeholders. Essentially, it's about finding the best possible compromise or balance between different factors or goals. Some of the key considerations for setting trade-offs and priorities in system design include: Requirement Analysis: This involves analyzing the system's requirements and constraints to determine the most important and critical aspects of the system. Risk Analysis: This involves identifying potential risks and uncertainties in the system design, and assessing their impact on the system's performance and behavior.

Cost-Benefit Analysis: This involves analyzing the costs and benefits associated with different design options and making informed decisions about the most effective use of resources. Performance Optimization: This involves optimizing the system's performance and behavior to meet the most critical and important requirements while minimizing the impact of trade-offs and constraints. Iterative Design: This involves iterating and refining the system design based on feedback from stakeholders and users, and making adjustments to priorities and trade-offs as necessary. Overall, setting trade-offs and priorities in system design is a critical aspect of the design process, and requires careful consideration of the system's requirements, constraints, and priorities. By making informed decisions about the allocation of resources and functionality, system designers can develop systems that meet the most critical and important requirements, while minimizing the impact of constraints and trade-offs.

9. Common Architecture Styles There are several common architecture styles in system design, including: Client-server architecture: This architecture involves a client application that communicates with a server to request services or resources. The server then provides the requested services or resources to the client. This architecture is often used for web applications, where the client is a web browser and the server is a web server. Microservices architecture: In this architecture, a system is broken down into a collection of small, independent services that communicate with each other to perform tasks. Each microservice is responsible for a specific function, and can be developed, deployed, and scaled independently. Event-driven architecture: This architecture is based on the idea of events and messages. Applications send and receive messages, and events trigger actions

within the system. This architecture is often used for real-time applications, such as stock trading or IoT systems. Layered architecture: This architecture involves breaking down a system into layers, with each layer providing a specific set of services or functionality. The layers communicate with each other through defined interfaces, and each layer only interacts with the layer directly below it. Monolithic architecture: In this architecture, the entire system is developed and deployed as a single unit. This architecture is simple and easy to develop, but can be difficult to scale and maintain over time. These are just a few examples of common architecture styles in system design. The choice of architecture will depend on the specific requirements of the system and the preferences of the development team.

Architecture of ATM system The architecture of an ATM (Automated Teller Machine) system can be designed using object-oriented class designing principles. Here is a sample architecture of an ATM system: User Interface Class: This class handles the user interface of the ATM, including displaying options and messages to the user and receiving input from the user. Account Class: This class represents the user's account information, including account number, PIN, and balance. It also provides methods to access and modify the account information, such as checking the balance, depositing funds, and withdrawing funds. Bank Class: This class represents the bank that operates the ATM. It provides methods to authenticate user accounts and validate transactions, such as checking if the user's PIN is correct and if the account has sufficient funds. Transaction Class: This class represents a single transaction that a user performs on the ATM, such as withdrawing cash or checking the account

balance. It includes information such as the type of transaction, the amount of funds involved, and the time and date of the transaction. Cash Dispenser Class: This class represents the cash dispenser mechanism of the ATM. It provides methods to dispense cash to the user, based on the user's requested amount and the availability of funds in the ATM. Receipt Printer Class: This class represents the receipt printer mechanism of the ATM. It provides methods to print receipts for each transaction that the user performs, including the transaction type, amount, and time. These classes can be organized into a hierarchy, with the User Interface class at the top level and the other classes as sub-levels. The Bank class can also be further subdivided into more specific classes, such as the Authorization Class for authenticating user accounts, and the Transaction Validation Class for validating transactions. Overall, this architecture provides a clear separation of concerns, allowing for easy maintenance and modification of the ATM system.

Module - 8

Programming styles

Object oriented style

Object-oriented programming (OOP) is a programming paradigm that is based on the concept of "objects", which can contain data and code to manipulate that data. In OOP, software is organized around objects that interact with each other to perform tasks. 1. Reusability : Reusability is an important concept in object-oriented programming (OOP) that refers to the ability to reuse existing code in new contexts or projects. In OOP, reusability is achieved through the use of classes and objects. By creating classes with well-defined properties and methods, developers can create code that can be used again and again in different parts of an application or in different applications altogether. This can save time and effort in development, as well as make code easier to maintain and update. One way that OOP achieves reusability is through inheritance. Inheritance allows new classes to be created that inherit properties and methods from existing classes. This can save time and effort in development by allowing developers to reuse existing code, rather than starting from scratch. Another way that OOP achieves reusability is through the use of interfaces. Interfaces define a set of methods that a class must implement in order to be considered compatible with the interface. By implementing an interface, a class can be used in different contexts where that interface is required, regardless of its specific implementation. Overall, reusability is an important concept in OOP that allows developers to write code that can be used and reused in different contexts. By creating well-defined classes and interfaces, developers can create code that is easier to maintain, update, and reuse in the future.

2. Extensibility : Extensibility is another important concept in object-oriented programming (OOP) that refers to the ability to easily extend and modify existing code to accommodate new requirements or functionality.

In OOP, extensibility is achieved through the use of inheritance, interfaces, and polymorphism. By creating well-designed classes and interfaces, developers can create code that can be easily extended and modified without affecting the existing code.p Inheritance allows new classes to be created that inherit properties and methods from existing classes, which can then be extended or overridden as needed. This allows for the creation of new functionality without modifying the existing code, making it easier to maintain and update. Interfaces provide a way to define a set of methods that a class must implement in order to be considered compatible with the interface. This allows for the creation of new classes that can be used in place of existing classes, as long as they implement the required interface. Polymorphism allows for the use of objects of different types in the same way, which can make code more flexible and adaptable. By defining methods with the same signature in different classes, those methods can be used interchangeably, regardless of the specific class of the object. Overall, extensibility is an important concept in OOP that allows developers to create code that can be easily extended and modified to meet changing requirements or functionality. By creating well-designed classes and interfaces, developers can create code that is easier to maintain, update, and extend in the future.

3. Robustness : Robustness is an important concept in object-oriented programming (OOP) that refers to the ability of a program to handle unexpected or erroneous inputs and situations without crashing or producing incorrect results. In OOP, robustness is achieved through a combination of techniques and best practices. One important technique is exception handling, which allows programs to detect and handle errors in a structured way. By using try-catch blocks, for example, developers can catch exceptions and take appropriate action, such as displaying an error message or retrying an operation.

Another important technique for achieving robustness is defensive programming, which involves anticipating and handling potential errors and unexpected inputs. For example, validating user inputs and checking for null values can help prevent errors from occurring. In addition, OOP provides several features that can help improve the robustness of a program. Encapsulation, for example, can help prevent unintended modifications to the state of an object, while inheritance and polymorphism can make code more flexible and adaptable. Overall, robustness is an important concept in OOP that allows programs to handle unexpected inputs and situations without crashing or producing incorrect results. By using techniques like exception handling and defensive programming, as well as leveraging the features of OOP, developers can create code that is more robust and resilient to errors.

4. Programming-in-the-large : Programming in the large is a concept in object-oriented programming (OOP) that refers to the development of large-scale software systems. In large-scale systems, OOP can be used to create modular and maintainable code that is easier to develop, test, and maintain. In OOP, programming in the large typically involves the use of design patterns, which are standardized solutions to common programming problems. Design patterns can help developers create code that is reusable, extensible, and maintainable. Another important aspect of programming in the large is software architecture, which refers to the overall structure of a software system. In OOP, software architecture can be designed using patterns like the Model-View-Controller (MVC) pattern, which separates the user interface, business logic, and data storage components of a system into separate modules. This can make it easier to develop and maintain large-scale systems by allowing developers to focus on specific parts of the system without worrying about the rest.

Programming in the large also involves techniques for managing complexity, such as abstraction and encapsulation. Abstraction allows developers to hide the details of a component's implementation from the rest of the system, while encapsulation allows developers to define the interface for a component and hide its internal workings. Overall, programming in the large is an important aspect of OOP that involves designing and developing large-scale software systems using techniques like design patterns, software architecture, and managing complexity. By using these techniques, developers can create software systems that are modular, maintainable, and easy to develop and test.