UML is a standard language for specifying, visualizing, constructing, and documenting the artifacts of software systems. It is also used for business modeling and other non-software systems.The features of UML are as follows:

Represents a collection of best engineering practices that have proven successful in the modeling of large and complex systems.

It also offers a standard way to write blueprints of a system. It includes conceptual things, such as business processes and system functions. It also offers concrete things, such as programming language statements, database schema, and reusable software components.

The advantages of the UML are as follows: The UML provides the user with a ready-to-use, expressive visual modeling

language so that they can develop and exchange meaningful models. It offers extensibility and specialization mechanisms to extend the core concepts. It is independent of particular programming languages and development

processes. It provides a formal basis for understanding the modeling language. It supports higher-level development concepts, such as collaborations, framework,

patterns, and components. It also integrates the best practices.

The different types of UML diagrams are as follows:1. Use case diagram2. Class diagram3. Interaction diagrams, such as sequence and collaboration4. State diagram5. Activity diagram6. Physical diagrams, such as component and deployment

The two main components of a use case diagram are use cases and actors.1. The use case:

Is an external view of the system that represents the action performed to complete a task.It also describes a sequence of actions that provides value to an actor.

2. An actor represents a user or another system that will interact with the system that you are modeling.

The illustration displays the relationship between actors and use cases. 

To draw a use case diagram, start by listing all the users of the system. Then, think from the user’s perspective and list all the functionalities a user might want a system to provide.

For example, consider a library management system.First, identify all the users of the system, such as librarian, reader, and others.List the functionalities that an actor wants the system to provide, such as issuing the books, returning the books, purchasing the books, and browsing the catalog and view list.

A class diagram shows the existence of classes and their relationships in the logical view of a system.The UML modeling elements in class diagrams are as follows: Classes, their structure and behavior Relationship components among the classes, such as association, aggregation,

composition, dependency, and inheritance Multiplicity and navigation indicators Role names or labels

Class Diagrams use the following UML conventions. The syntax to perform the operations is displayed here.In the syntax, static members are underlined, but the instance members are not underlined.The parameter list will show each parameter type preceded by a colon. The access specifiers appear in front of each member.The table displayed here represents the various access specifiers.

In a class diagram, classes and objects are related in different types. They are as follows:

Association Aggregation Composition Inheritance Dependency Instantiation

An association relationship of a class diagram denotes a structural connection between two classes.

It shows a bi–directional connection between two classes. It is a weak coupling, as associated classes remain independent of each other.

An illustration for an association relationship is displayed here.

Example of class diagram:

There are two kinds of interaction diagrams. They are as follows: Sequence diagram, which is an interaction diagram that emphasizes the time

ordering of messages. Collaboration diagram, which is an interaction diagram emphasizing the

organization of objects participating in the interaction.

An example for a sequence diagram is displayed here:

A collaboration diagram illustrates the interaction between the objects by using a static spatial structure. Numbering the messages indicates the sequence of messages. The UML uses a decimal numbering scheme.The components of a collaboration diagram are as follows:

Links: It is represented by a continuous line between objects, and it indicates the exchange of messages.

Named objects Messages

A collaboration diagram illustrates the interaction between the objects by using a static spatial structure. Numbering the messages indicates the sequence of messages. The UML uses a decimal numbering scheme.The components of a collaboration diagram are as follows:

Links: It is represented by a continuous line between objects, and it indicates the exchange of messages.

Named objects Messages

An example for a collaboration diagram is displayed here.

In this session, you have learned that: UML is a standard language for specifying, visualizing, constructing, and

documenting the artifacts of software systems UML represents higher-level development concepts, such as collaborations,

framework, patterns, and components A use case diagram displays the relationship among actors and use cases A class diagram shows the existence of classes and their relationships in the

logical view of a system Interaction diagrams describe how groups of objects collaborate to accomplish

the tasks within the operation of the system

Advanced UML Diagrams:

State diagrams are used to describe the behavior of a system. They describe all the possible states of an object as events occur. Each diagram usually represents objects of a single class. State diagrams track the different states of its objects through the system.

The components of a state diagram are as follows: State Event State transition Action

The example diagram displayed here models the login part of an online banking system. Logging in consists of entering a valid social security number, personal id number, and then submitting the information for validation.Logging in can be factored into four non-overlapping states: Getting SSN, Getting PIN, Validating, and Rejecting. From each state comes a complete set of transitions that determine the subsequent state.

In the given example,

States are represented with the rounded rectangles. Transitions are represented by the arrows from one state to another. Events or conditions that trigger transitions are written beside the arrows. In the illustration, there are two self-transitions, one on Getting SSN and another

on Getting PIN. The initial state, that is, the black circle is a dummy to start the action. Final states are also dummy states that terminate the action.

The action that occurs as a result of an event or condition is expressed in the form of action. While in its validating state, the object does not wait for an outside event to trigger a transition. Instead, it performs an activity. The result of that activity determines its subsequent state.

An activity diagram is used to model a single operation of a business process. While a state chart diagram focuses attention on an object undergoing a process,

an activity diagram focuses on the flow of activities involved in a single process. The activity diagram shows how those activities depend on one another. It is used to describe a complicated algorithm. It is also used to model applications with parallel processes.

The components of an activity diagram are as follows: Activities Transitions Decision points or branches Synchronization bars

An illustration for an activity diagram is displayed here.This illustration depicts the functions of withdrawing money from a bank account through an ATM.

An activity diagram can be divided into object swim lanes that determine the responsibility of the objects.

A single transition comes out of each activity, connecting it to the next activity. A transition may branch into two or more mutually exclusive transitions. Guard expressions (inside [ ]) label the transitions coming out of a branch. A branch and its subsequent merge, which marks the end of the branch, appear in

the diagram as hollow diamonds. A transition may fork into two or more parallel activities.

The fork and the subsequent join of the threads, which come out of the fork, appear in the diagram as solid bars.

Physical diagrams are of two types. They are as follows: Component diagram Deployment diagram

COMPONENT DIAGRAMCOMPONENT DIAGRAM

A component diagram illustrates the organization and dependencies among software components.

This diagram displays how software components, including source code, binary code, and executable components are related.

This has components (A component represents physical packaging of a code module) and dependencies that are the relationships.

A component is as follows: A source code component A run-time component An executable component

DEPLOYMENT DIAGRAMDEPLOYMENT DIAGRAM

A deployment diagram shows the physical relationship between software and hardware in a system.

These diagrams include nodes, which represent a computational unit; in most cases, a piece of hardware.

It also includes connections between nodes, which shows the communication path over the system.

For example, the connections may represent direct hardware coupling line RS-232 cable. An Ethernet connection may also represent indirect coupling, such as satellite-to-ground communication.

An example for a physical diagram is displayed here.

In this session, you have learned that: State diagrams are used to describe the behavior of a system An activity diagram is used to model a single operation of a business process The two types of physical diagrams are component and deployment