UML  UML stands for Unified Modeling Language. It is a standard which is mainly used for creating object- oriented, meaningful documentation models for any software system present in the real world.  It provides us a way to develop rich models that describe the working of any software/hardware systems.  Characteristics of UML 1. It is a generalized modeling language. 2. It is different from software programming languages such as Python, C, C++, etc. 3. It is a pictorial language which can be used to generate powerful modeling elements. 4. It is related to object-oriented designs and analysis. 5. It has unlimited applications even outside the software industry. It can be used to visualize the workflow of a factory.

Cont..  Following object-oriented concepts are required to begin with UML: Object: It is a real-world entity. There are multiple objects available within a single system. It is a fundamental building block of UML. Class: A class is nothing but a container where objects and their relationships are maintained. Abstraction: It is a mechanism of representing an entity without showing the implementation details. It is used to visualize the behavior of an object. Inheritance: It is a mechanism of extending an existing class to create a new class. Polymorphism: It is a mechanism of representing an object having multiple forms which are used for different purposes. Encapsulation: It is a method of binding the object and the data together as a single unit. It ensures tight coupling between the object and the data.

Types of UML Diagram  UML is linked with object oriented design and analysis. UML makes the use of elements and forms associations between them to form diagrams. Diagrams in UML can be broadly classified as: Structural Diagrams – Capture static aspects or structure of a system. Structural Diagrams include: Component Diagrams, Object Diagrams, Class Diagrams and Deployment Diagrams. Behavior Diagrams – Capture dynamic aspects or behavior of the system. Behavior diagrams include: Use Case Diagrams, State Diagrams, Activity Diagrams and Interaction Diagrams.

UML Tools  There are many tools available in the market to generate UML diagrams. Some are desktop based while others can be used online. Following list of tools which can be used for the creation of UML models: Star UML Argo UML Dia Visual Paradigm U-Model UML lab Enterprise Architect

Purpose of UML  What're the Purposes of UML? To reason about system behavior. To detect errors and omissions early in the life cycle. To present proposed designs and communicate with stakeholders. To understand requirements. To drive implementation.

UML Use Case Diagram  Purpose 1. Use case diagram is used during the analysis phase of a project to identify the system functionality. It describes the interaction of people or external device with the system under design. 2. It doesn't show much detail, but only summarizes some of the relationships between use cases, actors, and systems.  Usage 1.Basically four elements need to be included in use case diagram. 2.They are actors, system, use case, and relationship. Actors represent whoever or whatever interact with the system. 3.They can be humans, other computers, or other software systems. 4.Use cases represent the actions that are performed by one or more actors for a particular goal. System is whatever you are developing.

UML Use Case Symbols

Example for use case

Class Diagram class diagram describes the attributes and operations of a class and also the constraints imposed on the system. The class diagrams are widely used in the modeling of object oriented systems because they are the only UML diagrams, which can be mapped directly with object-oriented languages. Class diagram shows a collection of classes, interfaces, associations, collaborations, and constraints. It is also known as a structural diagram. 1. The purpose of the class diagram can be summarized as − 2. Analysis and design of the static view of an application. 3.Describe responsibilities of a system. 4.Base for component and deployment diagrams. 5.Forward and reverse engineering.

How to Draw a Class Diagram?  The following points should be remembered while drawing a class diagram The name of the class diagram should be meaningful to describe the aspect of the system. Each element and their relationships should be identified in advance. Responsibility (attributes and methods) of each class should be clearly identified For each class, minimum number of properties should be specified, as unnecessary properties will make the diagram complicated. Use notes whenever required to describe some aspect of the diagram. At the end of the drawing it should be understandable to the developer/coder. Finally, before making the final version, the diagram should be drawn on plain paper and reworked as many times as possible to make it correct.

Benefits of Class Diagram Class Diagram Illustrates data models for even very complex information systems It provides an overview of how the application is structured before studying the actual code. This can easily reduce the maintenance time It helps for better understanding of general schematics of an application. Allows drawing detailed charts which highlights code required to be programmed Helpful for developers and other stakeholders.

Essential elements of A UML class diagram  Essential elements of UML class diagram are: 1. Class Name 2. Attributes 3. Operations  Following rules must be taken care of while representing a class: 1.A class name should always start with a capital letter. 2.A class name should always be in the center of the first compartment. 3.A class name should always be written in bold format. 4.An abstract class name should be written in italics format.  Attributes characteristics 1.The attributes are generally written along with the visibility factor. 2.Public, private, protected and package are the four visibilities which are denoted by +, -, #, or ~ signs respectively. 3.Visibility describes the accessibility of an attribute of a class. 4.Attributes must have a meaningful name that describes the use of it in a class.

Relationships  There are mainly three kinds of relationships in UML: 1.Dependencies 2.Generalizations 3.Associations 1.Dependency A dependency means the relation between two or more classes in which a change in one may force changes in the other. However, it will always create a weaker relationship. Dependency indicates that one class depends on another. 2. Generalization: generalization helps to connect a subclass to its super class. A sub-class is inherited from its super class. Generalization relationship can't be used to model interface implementation. Class diagram allows inheriting from multiple super classes.

Cont.. 3. Association: This kind of relationship represents static relationships between classes A and B. For example; an employee works for an organization.

Multiplicity  A multiplicity is a factor associated with an attribute. It specifies how many instances of attributes are created when a class is initialized.  If a multiplicity is not specified, by default one is considered as a default multiplicity.

Aggregation  Aggregation is a special type of association that models a whole- part relationship between aggregate and its parts.  Here, the college class will remain even if the student is not available.

Composition The composition is a special type of aggregation which denotes strong ownership between two classes when one class is a part of another class. Here if college is not functioning all the students also removed.

Example for class diagram