Components Of Sequence Diagram In Uml

Posted : admin On 17.08.2021
  1. Uml Sequence Diagram Decision
  2. Components Of Sequence Diagram In Uml Model
  3. Elements Of Sequence Diagram In Uml
  4. Uml Sequence Diagram Activation
  5. Sequence Diagram Adalah

Sequence Diagram Sequence Diagram is an interaction diagram that shows how processes operate with one another and in what order. It shows, as parallel vertical lines (lifelines), different processes or objects that live simultaneously, and as horizontally arrows, the message exchange between them in the order which they occur. The Ultimate Guide to Sequence Diagrams in UML - Includes a general overview, benefits and scenarios, basic symbols and components, examples, and more! Use this guide and create your own sequence diagram in UML for free with Lucidchart!

Sequence Diagrams

A sequence diagram is a form of interaction diagram which shows objects as lifelines running down the page, with their interactions over time represented as messages drawn as arrows from the source lifeline to the target lifeline. Sequence diagrams are good at showing which objects communicate with which other objects; and what messages trigger those communications. Sequence diagrams are not intended for showing complex procedural logic.


A lifeline represents an individual participant in a sequence diagram. A lifeline will usually have a rectangle containing its object name. If its name is 'self', that indicates that the lifeline represents the classifier which owns the sequence diagram.

Sometimes a sequence diagram will have a lifeline with an actor element symbol at its head. This will usually be the case if the sequence diagram is owned by a use case. Boundary, control and entity elements from robustness diagrams can also own lifelines.


Messages are displayed as arrows. Messages can be complete, lost or found; synchronous or asynchronous; call or signal. In the following diagram, the first message is a synchronous message (denoted by the solid arrowhead) complete with an implicit return message; the second message is asynchronous (denoted by line arrowhead), and the third is the asynchronous return message (denoted by the dashed line).


Execution Occurrence

A thin rectangle running down the lifeline denotes the execution occurrence, or activation of a focus of control. In the previous diagram, there are three execution occurrences. The first is the source object sending two messages and receiving two replies; the second is the target object receiving a synchronous message and returning a reply; and the third is the target object receiving an asynchronous message and returning a reply.

Self Message

A self message can represent a recursive call of an operation, or one method calling another method belonging to the same object. It is shown as creating a nested focus of control in the lifeline’s execution occurrence.

Lost and Found Messages

Lost messages are those that are either sent but do not arrive at the intended recipient, or which go to a recipient not shown on the current diagram. Found messages are those that arrive from an unknown sender, or from a sender not shown on the current diagram. They are denoted going to or coming from an endpoint element.

Lifeline Start and End

A lifeline may be created or destroyed during the timescale represented by a sequence diagram. In the latter case, the lifeline is terminated by a stop symbol, represented as a cross. In the former case, the symbol at the head of the lifeline is shown at a lower level down the page than the symbol of the object that caused the creation. The following diagram shows an object being created and destroyed.


Duration and Time Constraints

By default, a message is shown as a horizontal line. Since the lifeline represents the passage of time down the screen, when modelling a real-time system, or even a time-bound business process, it can be important to consider the length of time it takes to perform actions. By setting a duration constraint for a message, the message will be shown as a sloping line.

Combined Fragments

It was stated earlier that sequence diagrams are not intended for showing complex procedural logic. While this is the case, there are a number of mechanisms that do allow for adding a degree of procedural logic to diagrams and which come under the heading of combined fragments. A combined fragment is one or more processing sequence enclosed in a frame and executed under specific named circumstances. The fragments available are:
  • Alternative fragment (denoted “alt”) models if…then…else constructs.
  • Option fragment (denoted “opt”) models switch constructs.
  • Break fragment models an alternative sequence of events that is processed instead of the whole of the rest of the diagram.
  • Parallel fragment (denoted “par”) models concurrent processing.
  • Weak sequencing fragment (denoted “seq”) encloses a number of sequences for which all the messages must be processed in a preceding segment before the following segment can start, but which does not impose any sequencing within a segment on messages that don’t share a lifeline.
  • Strict sequencing fragment (denoted “strict”) encloses a series of messages which must be processed in the given order.
  • Negative fragment (denoted “neg”) encloses an invalid series of messages.
  • Critical fragment encloses a critical section.
  • Ignore fragment declares a message or message to be of no interest if it appears in the current context.
  • Consider fragment is in effect the opposite of the ignore fragment: any message not included in the consider fragment should be ignored.
  • Assertion fragment (denoted “assert”) designates that any sequence not shown as an operand of the assertion is invalid.
  • Loop fragment encloses a series of messages which are repeated.
The following diagram shows a loop fragment.

There is also an interaction occurrence, which is similar to a combined fragment. An interaction occurrence is a reference to another diagram which has the word 'ref' in the top left corner of the frame, and has the name of the referenced diagram shown in the middle of the frame.


A gate is a connection point for connecting a message inside a fragment with a message outside a fragment. EA shows a gate as a small square on a fragment frame. Diagram gates act as off-page connectors for sequence diagrams, representing the source of incoming messages or the target of outgoing messages. The following two diagrams show how they might be used in practice. Note that the gate on the top level diagram is the point at which the message arrowhead touches the reference fragment - there is no need to render it as a box shape.

Part Decomposition

An object can have more than one lifeline coming from it. This allows for inter- and intra-object messages to be displayed on the same diagram.

State Invariant / Continuations

A state invariant is a constraint placed on a lifeline that must be true at run-time. It is shown as a rectangle with semi-circular ends.

A continuation has the same notation as a state invariant, but is used in combined fragments and can stretch across more than one lifeline.

Unified Modelling Language (UML) is a type of language used to illustrate the inner workings of a system, which include its actors, actions, roles, and classes. Originally used in the fields of software and engineering, UML has now made its way into business, and is a popular method of documenting business processes.

UML primarily uses diagrams to represent systems. These diagrams can be broken down into two types: behavioural UML diagrams, and structural UML diagrams.

UML is an extremely versatile and widely-recognised language. It is the standard language used by many developers, as well as an increasing number of business professionals. Its flexibility means that it can be applied to a number of IT or business-related situations, so that you can make it applicable to the system or technology you are using.

Part 2: How to Make a UML Sequence Diagram Effortlessly?

How to make a UML sequence diagram easily? Using EdrawMax to create your own UML sequence diagram.

Step 1: Open EdrawMax desktop software or EdrawMax web-based application. Vs code insiders.

Step 2: Navigate to [New]>[Software Development]>[UML Modeling]

Step 3: Select one UML sequence diagram template to edit on it or click the [+] sign to start from scratch. Also, you can use massive UML sequence diagram symbols and elements from libraries in left menu to customize your UML sequence diagram.

Step 4: Once finished your creation, you can export the file in multiple formats, including Graphics, PDF, editable MS Office file, SVG and Visio vsdx file.

Step 5: Besides, you can share your UML sequence diagram with others via social media and web page. Or publish your UML sequence diagram in EdrawMax template gallery to show your work with others.

Uml Sequence Diagram Decision

Example1: Spring and Hibernate Transaction Sequence Diagram

Here, we provide an example of a UML sequence diagram that illustrates transaction management related to exception handling. The Spring application development framework for enterprise Java integrates Hibernate transaction management. When a certain business method is called, Spring Transaction Interceptor may intercept it. This creates a Hibernate session behind the background interceptor and starts a Hibernate JDBC transaction, so the business method will run in the context of the new transaction.

Example2: Facebook User Authentication Sequence Diagram

Components Of Sequence Diagram In Uml Model

This is an example of a UML sequence diagram, which shows how to authenticate Facebook users in a web application to allow access to their Facebook resources. Facebook uses the OAuth 2.0 protocol framework, which enables web applications (called 'clients') that are not normally Facebook resource owners but represent Facebook users to request access to resources controlled by Facebook users and hosted by Facebook servers. The web application obtains an access token instead of using Facebook user credentials to access protected resources.


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Elements Of Sequence Diagram In Uml

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Uml Sequence Diagram Activation

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Sequence Diagram Adalah

According to this article, there are mainly three parts to illustrate what is UML sequence diagram, to tell you how to create UML sequence diagrams and to show you some UML sequence diagram examples. Generally speaking, a UML sequence diagram can visually represent a system along with its main actors, roles, and actions in order to make people better understand the information about the system.

EdrawMax is an easiest all-in-one diagramming tool, you can create UML sequence diagrams and any other type diagrams with ease! With substantial UML sequence diagram symbols and cliparts, making UML sequence diagrams could be as simple as possible. Also, it supports to export your work in multiple formats and share your work with others. Get started to create your UML sequence diagrams now!