2/1/2022

Sequence Diagram Meaning

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  1. Sequence Diagram Meaning Pdf
  2. Sequence Diagram Meaning Definition
  3. Sequence Diagram Components Meaning
  4. Sequence Diagram Dashed Line Meaning
  1. Introduction

Sequence Diagram Meaning Pdf

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The sequence diagram represents the flow of messages in the system and is also termed as an event diagram. It helps in envisioning several dynamic scenarios. It portrays the communication between any two lifelines as a time-ordered sequence of events, such that these lifelines took part at the run time. In UML, the lifeline is represented by a vertical bar, whereas the message flow is represented by a vertical dotted line that extends across the bottom of the page. A sequence diagram emphasizes the time ordering (sequence) of messages. During the systems design phase, the sequence diagrams are refined to derive the methods and interactions between classes. Messages from one class are used to identify class relationships. UML 2 Tutorial - Sequence Diagram 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. 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. The second of the two steps in building the sequence diagram is to Please select the best answer. Define how the system uses the problem domain resources B. Define how the actor uses the system resources C. Define how the resource objects interact with the system D.

The UML includes interaction diagrams to illustrate how objects interact via messages. They are used for dynamic object modeling. There are two common types: sequence and communication interaction diagrams. This chapter introduces the notation—view it as a reference to skim through—while subsequent chapters focus on a more important question: What are key principles in OO design?
This chapter is from the book
Applying UML and Patterns: An Introduction to Object-Oriented Analysis and Design and Iterative Development, 3rd Edition
Time sequence diagram

This chapter is from the book

This chapter is from the book

Applying UML and Patterns: An Introduction to Object-Oriented Analysis and Design and Iterative Development, 3rd Edition

Cats are smarter than dogs. You can't get eight cats to pull a sled through snow.

Jeff Valdez

Objectives

  • Provide a reference for frequently used UML interaction diagram notation—sequence and communication diagrams.

Introduction

The UML includes interaction diagrams to illustrate how objects interact via messages. They are used for dynamic object modeling. There are two common types: sequence and communication interaction diagrams. This chapter introduces the notation—view it as a reference to skim through—while subsequent chapters focus on a more important question: What are key principles in OO design?

In the following chapters, interaction diagrams are applied to help explain and demonstrate object design. Hence, it's useful to at least skim these examples before moving on.

The Sequence diagram of UML

Sequence Diagram Meaning Definition

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.

Sequence diagram online

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 Components Meaning

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.

Sequence Diagram Dashed Line Meaning

References[edit]

  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.
Sequence Diagram Meaning

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
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