Sequence Diagram Basics

SequenceDiagram.org is an online tool / software for creating UML sequence diagrams. The efficiency when creating and working with sequence diagrams by combining text notation scripting and drawing by clicking and dragging in the. Sequence Diagrams – A sequence diagram simply depicts interaction between objects in a sequential order i.e. The order in which these interactions take place. We can also use the terms event diagrams or event scenarios to refer to a sequence diagram. Sequence diagrams describe how and in what order the objects in a system function.

  • Sequence Diagram is an interaction diagram that details how operations are carried out - what messages are sent and when. Sequence diagrams are organized according to time. The time progresses as you go down the page. The objects involved in the operation are listed from left to right according to when they take part in the message sequence.
  • Sequence diagrams are an excellent tool for looking at the big picture of object interaction. I like to call it a view from the above, which gives a structured view without reviewing each class.
  • 3/5/2021 Purpose of Sequence Diagrams and Basic Steps to Create One 2/4 As mentioned the aim of a sequence diagram is to define event sequences, which would have a desired outcome. The focus is more on the order in which messages occur than on the message per se.
The Sequence diagram of UML

A sequence diagram shows object interactions arranged in time sequence. It depicts the objects involved in the scenario and the sequence of messages exchanged between the objects needed to carry out the functionality of the scenario. Sequence diagrams are typically associated with use case realizations in the logical view of the system under development. Sequence diagrams are sometimes called event diagrams or event scenarios.

A sequence diagram shows, as parallel vertical lines (lifelines), different processes or objects that live simultaneously, and, as horizontal arrows, the messages exchanged between them, in the order in which they occur. This allows the specification of simple runtime scenarios in a graphical manner.

Diagram building blocks[edit]

If the lifeline is that of an object, it demonstrates a role. Leaving the instance name blank can represent anonymous and unnamed instances.

Messages, written with horizontal arrows with the message name written above them, display interaction. Solid arrow heads represent synchronous calls, open arrow heads represent asynchronous messages, and dashed lines represent reply messages.[1]If a caller sends a synchronous message, it must wait until the message is done, such as invoking a subroutine. If a caller sends an asynchronous message, it can continue processing and doesn’t have to wait for a response. Asynchronous calls are present in multithreaded applications, event-driven applications and in message-oriented middleware. Activation boxes, or method-call boxes, are opaque rectangles drawn on top of lifelines to represent that processes are being performed in response to the message (ExecutionSpecifications in UML).

Objects calling methods on themselves use messages and add new activation boxes on top of any others to indicate a further level of processing. If an object is destroyed (removed from memory), an X is drawn on bottom of the lifeline, and the dashed line ceases to be drawn below it. It should be the result of a message, either from the object itself, or another.

Sequence Diagram Basics Pdf

A message sent from outside the diagram can be represented by a message originating from a filled-in circle (found message in UML) or from a border of the sequence diagram (gate in UML).

UML has introduced significant improvements to the capabilities of sequence diagrams. Most of these improvements are based on the idea of interaction fragments[2] which represent smaller pieces of an enclosing interaction. Multiple interaction fragments are combined to create a variety of combined fragments,[3] which are then used to model interactions that include parallelism, conditional branches, optional interactions.


  1. ^OMG (2011). OMG Unified Modeling Language (OMG UML), Superstructure, V2.4.1, p. 507.
  2. ^OMG (2008). OMG Unified Modeling Language (OMG UML), Superstructure, V2.1.2, p. 485.
  3. ^OMG (2007). OMG Unified Modeling Language (OMG UML), Superstructure, V2.1.2. p. 467.

External links[edit]

Wikimedia Commons has media related to Sequence diagrams.
  • UML Distilled by Martin Fowler
  • Current UML Specification by Object Management Group (OMG)
  • Introduction to UML 2 Sequence Diagrams by Scott W. Ambler.
  • A Quick Introduction to UML Sequence Diagrams by Yanic Inghelbrecht
Sequence diagram basics pdf

Sequence Diagram Basics

Retrieved from 'https://en.wikipedia.org/w/index.php?title=Sequence_diagram&oldid=1019345802'
  • 1sequence diagram

    Большой англо-русский и русско-английский словарь >sequence diagram

  • 2sequence diagram

    Англо-русский технический словарь >sequence diagram

  • 3sequence diagram

    1) Техника:схема последовательности операций, схема последовательности сигналов
    2) Вычислительная техника:диаграмма последовательности
    3) Программирование:диаграмма последовательности (действий)

    Универсальный англо-русский словарь >sequence diagram

  • 4sequence diagram

    English-Russian dictionary of technical terms >sequence diagram

  • 5sequence diagram

    диаграмма, показывающая взаимодействие классов при решении некоторой задачи (например, представляющая порядок прохождения сообщений между объектами или компонентами системы для реализации некотого поведения)

    Англо-русский толковый словарь терминов и сокращений по ВТ, Интернету и программированию. >sequence diagram

  • 6sequence diagram

    English-Russian scientific dictionary >sequence diagram

  • 7sequence diagram

    English-Russian information technology >sequence diagram

  • 8sequence-of-operation diagram

    Универсальный англо-русский словарь >sequence-of-operation diagram

  • 9sequence-of-operation diagram

    Англо-русский словарь по гражданской авиации >sequence-of-operation diagram

  • 10sequence-of-operation diagram

    Англо-русский словарь по авиации >sequence-of-operation diagram

  • 11sequence logic diagram

    English-Russian industrial glossariy >sequence logic diagram

Sequence Diagram Basics Tutorial

См. также в других словарях:

Sequence Diagram Online

  • Sequence diagram — A sequence diagram is a kind of interaction diagram in UML, that shows how processes operate one with another and in what order. It is a construct of a Message Sequence Chart. Overview A sequence diagram shows, as parallel vertical lines (… … Wikipedia

  • System Sequence Diagram — In software engineering, a System Sequence Diagram (SSD) is a sequence diagram that shows, for a particular scenario of a use case, the events that external actors generate, their order, and possible inter system events. System sequence diagrams… … Wikipedia

  • Diagram — Further information: Chart Sample flowchart representing the decision process to add a new article to Wikipedia. A diagram is a two dimensional geometric symbolic representation of information according to some visualization technique. Sometimes … Wikipedia

  • Séquence principale — Le diagramme de Hertzsprung Russell figure les étoiles. En abscisse, l indice de couleur (B V) ; en ordonnée, la magnitude absolue. La séquence principale se voit comme une bande diagonale marquée allant du haut à gauche au bas à droite. Ce… … Wikipédia en Français

  • Communication diagram — Example of a Communication diagram. UML diagrams Structural UML diagrams Class diagram … Wikipedia

  • Interaction overview diagram — in the Unified Modeling Language (UML) is a type of activity diagram in which the nodes represent interaction diagrams. They are a s high level structuring mechanism for sequence diagrams. Interaction overview diagrams illustrate an overview of a … Wikipedia

  • Hubble sequence — The Hubble sequence is a morphological classification scheme for galaxies invented by Edwin Hubble in 1936.cite book last=Hubble first=E. P. authorlink=Edwin Hubble title=The Realm of the Nebulae year=1936 publisher=Yale University Press… … Wikipedia

  • Object diagram — Example of a Object diagram. UML diagrams Structural UML diagrams … Wikipedia

  • Composite structure diagram — UML diagrams Structural UML diagrams Class diagram Component diagram Composite structure diagram Deployment diagram Object diagram … Wikipedia

  • Class diagram — UML diagrams Structural UML diagrams Class diagram Component diagram Composite structure diagram Deployment diagram Object diagram … Wikipedia

  • Deployment diagram — A sample deployment diagram UML diagrams Structural UML diagrams … Wikipedia