Sequence Diagram Parts

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How can I show goto statements in Sequence Diagrams. For example in the diagram below, once 'sleep till hold period' is expired I want to take control back to the 'isiteminventoryonholdstate(itemid)' statement.

  1. Sequence Diagram Tutorial
  2. Project Sequence Diagram

What Is A Physical Network Diagram?

Sequence diagrams are commonly used by developers to depict interactions between objects in a use case (actions that show interactions between an actor and a system to achieve a goal). Such diagrams typically illustrate how different parts of a system interact with each other, and in what order, to achieve an outcome. They are most commonly used by software developers but have been increasingly adopted within business settings as well, due to its ability to show how a system operates clearly.

How Can a Sequence Diagram Helps You?

Sequence diagrams are commonly used by developers to depict interactions between objects in a use case (actions that show interactions between an actor and a system to achieve a goal). Such diagrams typically illustrate how different parts of a system interact. Sequence diagrams can be used to explore the logic of a complex operation, function, or procedure. One way to think of sequence diagrams, particularly highly detailed diagrams, is as visual object code. The logic of services. A service is effectively a high-level method, often one that can be invoked by a wide variety of clients.

So when should sequence diagrams be used, and what can they be used for?

  • To illustrate interactions between actors (system users) and the system, or various parts of a system.
  • To show the time order in which events occur.
  • To be used as a handy form of documentation on how a system functions. This documentation can be passed on to other persons or organizations.

Sequence Diagram Symbols

Now that we have discussed what it is and its purpose, let’s take a look at some commonly used symbols and components in a sequence diagram.

Sequence Diagram Parts
Object Lifeline

Objects or parts of a system that interact during the sequence.

Alternative Fragment

Two or more message sequences exist, and a choice must be made between the two of them.

Loop Fragment

Represents a repetitive sequence.

Choice Fragment

A sequence can only occur under certain circumstances. Otherwise, it will fail.


Represents an active object during an interaction between two objects. The length of the bar represents the duration of an object’s activeness.

Object Deletion

Ends the lifeline of objects or messages.


Can be a human user or other external subjects.


Represents system data.


Represents software element in a system.


Organizes entity and boundary elements.


Used to contain additional useful information for the modeller/developer.


Sender of the message must wait for the receiver to process the message before continuing to send another message.

Message Return

Receiver of the message passes information back to the sender.

Asynchronous message

Message sender continues sending messages without waiting for the receiver to process its messages.

Self delegation

When an object sends a message to itself.

End point

How to Draw a Sequence Diagram in EdrawMax?

Sequence diagram parts list

EdrawMax’s intuitive software allows you to create your sequence diagrams. Follow this outline to create one that fits your needs with minimum effort.

  • Step 1: In your browser, visit https://www.edrawmax.com/online/ to access the online version, or download the desktop version at https://www.edrawsoft.com/download-edrawmax.html
  • Step 2: In the white sidebar, click on Software Development. Then, click on the UML Modelling box that appears near the top of the screen.
  • Step 3: Choose a template, or click on the UML Modelling box with the “ + ” to open a new document. Alternatively, you may type in “sequence diagram” in the search bar above and use a ready-made template.
  • Step 4: The symbol library can be found to the left of the screen. Scroll down further to find more sequence diagram-related symbols.
  • Step 5: Simply drag the components you need from the symbol library onto the blank document to start creating. Each element can be moved, resized, or customized to fit your needs.

Sequence Diagram Examples

Here are examples of sequence diagrams created on EdrawMax.


Diagram 1: a customer logging into their online shopping account. This diagram shows what occurs during the verification process.

Diagram 2: ATM withdrawal. This diagram shows what interactions occur between the customer, the ATM machine and the bank during a cash withdrawal.

Key Takeaways

In any seemingly simple operation, there are always multiple parts interacting to create a certain outcome. Sequence diagrams are a fantastic way of visualizing and illustrating complex processes, allowing you to break down all of the interactions and see how a system operates on a macro scale. Use Edraw Max’s sequence diagram tools to create your sequence diagrams now!

Sequence Diagram Tutorial

The sequence diagram is part of UML’s behavioral suite of diagrams, used to show interaction between tow of more object in the context of time as they occur.

The sequence diagrams typically show the logical view of the system and interactions with it in form of events in one or more scenarios, therefore sometimes sequence diagram is also called event diagram.

“A sequence diagram is a dynamic model that shows the explicit sequence of messages that are passed between objects in a defined interaction. Because sequence diagrams emphasize the time-based ordering of the activity that takes place among a set of objects, they are very helpful for understanding real-time specifications and complex use cases.” Dennis, A., Wixom, B. H., & Tegarden, D. P. (2015).

Project Sequence Diagram

Main building blocks of sequence diagrams are actors, lifeline, objects, guard condition, execution occurrence and message. Lifeline represents each participating actor, its interactions during over the time. It is represented by the box with vertical dotted line such as following.

An object represents the other parts of system where messages are sent and received. An execution occurrence show sending or receiving of message in the context of time frame.

The message represents an event of sequence diagram in the form of request or response. It is denoted by arrow going left to right for request of event and from right to left for response of the event or action such as following.

Message can be either synchronous asynchronous. The synchronous message is denoted by solid head arrow, and asynchronous is represented by a regular arrow sign.

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Sequence Diagram Parts

Finally, the guard condition ensures the constraint or condition needs to be satisfied in order to send the message to system.

Steps used to create a sequence diagram

The sequence diagrams are a greater way to model usage behavior of the system in terms of timeline interactions of actors. The sequence diagram can be generic to show the general behaviors of the system, or it can be specific to instance. Single scenario-based sequence diagrams are recommended way to model in real-world software systems.

Let’s take an example of patient appointment system, where patient comes in for appointment scheduling, the logical flow of the interactions would be request appointment to receptionist. The receptionist would check the system to see if patient is new or exiting.

If in the case of new patient, he is asked to fill paperwork, and in the case of existing patient, receptionist check patent system to see if he or she has any unpaid bills and then schedule appointment based on availed time slots with physicians. If we were to draw a sequence diagram what would be the flow?

First, we will extract the actors in the system which is patient, receptionist, patient system, unpaid-bills and appointment module.

All the actors in this image are drawing with their lifeline, and the arrows show the messages flowing through the system.

The patient and receptionist are actors in the system, Patient, Unpaid-Bill and Appointment also represents objects in the system. Lookup patient is guard condition to check if patient already exists, based on what different messages are sent within the system.

The execution timeline is drawn as vertical boxes. The messages are flowing through the system in forward and back depending upon the action and response.