Introduction to UML

Introduction to UML

• UML stands for Unified Modeling Language
• It is a general-purpose graphical modeling language used in software engineering
• UML diagrams are used to describe, analyze, discover, and test a system's characteristics and behaviors
• UML was initially developed by Grady Booch, Ivar Jacobson, and James Rumbaugh in 1994-95 at Rational Software
• In 1997, UML was adopted as a standard by the Object Management Group

Goals of UML

• UML aims to provide users with an expressive, ready-to-use visual modeling language for model development and exchange
• It offers extensibility and specialization mechanisms to expand core concepts
• UML is designed to be independent of specific programming languages and development processes
• A goal is to provide a formal basis for understanding the modeling language
• UML supports higher-level development concepts like collaborations, frameworks, patterns, and components
• Integration of best practices is a key goal

Characteristics of UML

• UML is a generalized modeling language
• It is distinct from programming languages like C++ and Python
• UML is interrelated with object-oriented analysis and design
• It is used to visualize the workflow of a system
• UML is pictorial, generating powerful modeling artifacts

UML Building Blocks

• UML consists of three main building blocks: things, relationships, and diagrams
• Building blocks are combined to generate a UML model diagram
• The basic UML building blocks are things, relationships, and diagrams

Things

• Things are the most important building blocks in UML
• They can be structural, behavioral, grouping, or annotational

Structural Things

• Structural things depict the static behavior and display physical and conceptual components of a model
• Include classes, objects, interfaces, nodes, collaborations, components, and use cases
• Class: A class outlines the functionality and properties of identical things

Objects and Interfaces

• Object: An object describes the behavior and functions of a system
• Its notation is similar to a class, but the object name is underlined
• Interface: An interface is a set of operations that describes the functionality of a class

Collaboration and Use Case

• Collaboration: Represents the interaction between things to meet a goal and is drawn as a dotted ellipse
• Use case: It portrays a set of actions executed by a system to achieve a goal

Actor, Component and Node

• Actor: Found in use case diagrams and interacts with the system
• Component: Represents the physical part of the system
• Node: Represents a physical element that exists at run time

Behavioral Things

• Behavioral things represent the dynamic parts of UML models
• There are three primary types of behavioral things: interaction, state machine, and activity

Interaction

• Interaction is a behavior that comprises a set of messages exchanged among a set of objects or roles within a specific context for a specific purpose
• The behavior of a society of objects or individual operation may be specified with an interaction
• An interaction involves messages, actions, and connectors between objects, represented graphically as a directed line including the operation name

State Machine

• State machine specifies the sequences of states an object or interaction goes through during its lifetime in response to events
• It includes states, transitions (flow from state to state), events (triggering transitions), and activities (responses to transitions)
• A state is graphically represented as a rounded rectangle, including its name and substates

Activity

• Activity specifies the sequence of steps a computational process performs
• Interactions focus on the set of objects interacting
• State machines focus on the lifecycle of one object at a time
• Activities focus on the flows between steps, regardless of which object performs each step
• An action is a step of an activity
• Actions are rendered as rounded rectangles with the purpose of the action specified
• States and actions are distinguished by their context

Grouping and Annotational Things

• Grouping things bind the elements of the UML model together
• Packages are the primary grouping thing, serving as a general-purpose mechanism for organizing design
• Packages are purely conceptual and exist only at development time
• Graphically, a package is represented as a tabbed folder, usually with only its name and content
• Annotational things are explanatory parts of UML models
• Notes are the primary annotational thing, used for constraints and comments attached to a single or collection of elements
• Notes are rendered as a rectangle with a dog-eared corner and textual or graphical comments

Relationships

• Relationships illustrate meaningful connections between things, show associations between entities, and define application functionality
• The four types of relationships include dependency, association, generalization, and realization

Dependency, Association

• Dependency: A semantic relationship where a change to one model element can affect another. Graphically, it is a dashed line, possibly directed
• Association: A structural relationship among classes describing links or connections among objects.

Generalization, Realization

• Generalization: The specialized element (child) builds on the specification of the generalized element (parent)
• The child shares the structure and behavior of the parent. Graphically, it is a solid line with a hollow arrowhead
• Realization: A semantic relationship between classifiers, in which one classifier specifies a contract that another must carry out
• These often occur between interfaces/classes (or components) and use cases/collaborations.
• Graphically, it is a cross between generalization and dependency

Diagrams in UML

• UML includes 13 types of diagrams

Use Case Diagrams

• Use case diagrams are utilized in systems and software engineering
• They list actions or event steps, defining interactions between a role and system, for achieving goals

What are Use Cases, Actors

• A use case is a list of actions or event steps that define the interactions between a role, known as an actor in UML, and a system to achieve a goal
• The actor can be a human, an external system, or even time
• Use cases describe how a real-world actor interacts with the system

Importance of Use Cases

• Use cases have been used extensively over the past few decades
• Use cases provides a summary of system offerings, gives an overview of system component roles, and assists in defining roles and needs
• Use cases Advantages: provide a summary of system offerings, gives an overview of system component roles, and assists in defining roles and needs

Hospital Management System Use Case Diagrams

• A general use case diagram shows an Admin and a Patient
• The admin can:
• Manage Patients' Info and Status
• Manage Hospital Rooms info and Status
• Manage Hospital Transaction Records
• The diagram also shows the actors involved in Hospital system

Online Shopping System Use Case Diagrams

• Displays interactions with an online shopping system
• It has actors such as Registered Customer, New Customer, Web Customer, Authentication, Identity provider etc

Banking System Use Case Diagrams

• Displays interactions with a Banking System
• The actors are :Customer, Cashier, Bank, Manager and their use cases with inter-dependencies

Library Management System Use Case Diagrams

• It displays interactions with Library System
• The actors are: User, Students, Staff, Librarian etc with a set of options on the system

College Information System Use Case Diagrams

• Shows the basic College Management System
• Main actors: Admin, Students and employees with what they can do on the system

Practice Questions

• Common questions asked about Unified Modelling Language