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.
Chapter 7 Sequence Diagrams 123 7.1 Purpose 123 7.2 When Should You Create a Sequence Diagram? 124 7.3 The Sequence Diagram Frame 125 7.4 Lifelines 125 7.5 Messages 129 7.6 Destruction Occurrences 138 7.7 Execution Specifications 139 7.8 Constraints 141 7.9 Combined Fragments 144 7.10 Interaction Uses 151. . UML sequence diagrams made in Lucidchart are living documents; markup can be edited or added to anytime without the need to start over or change formatting. Users can easily customize their UML sequence diagrams with the extensive formatting capabilities of Lucidchart. UML shapes can be dragged right from the shape library onto the diagram. In Lucidchart, creating a sequence diagram from scratch is surprisingly simple. Just follow these steps: Open a blank document or start with a template. To the left of the editor, click 'Shapes' to open the Shape Library Manager.
Diagram building blocks
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.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.
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 which represent smaller pieces of an enclosing interaction. Multiple interaction fragments are combined to create a variety of combined fragments, which are then used to model interactions that include parallelism, conditional branches, optional interactions.
Lucid Sequence Diagram Example
- ^OMG (2011). OMG Unified Modeling Language (OMG UML), Superstructure, V2.4.1, p. 507.
- ^OMG (2008). OMG Unified Modeling Language (OMG UML), Superstructure, V2.1.2, p. 485.
- ^OMG (2007). OMG Unified Modeling Language (OMG UML), Superstructure, V2.1.2. p. 467.
|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
**MUST HAVE KNOWLEDGE USING Lucid.app**
NOTE 1: Must be a ‘top-level’ sequence diagram based on the given activity diagram or part of your activity diagram. The sequence diagram must capture the ‘data message’ flow in the system, the structural organization of the objects, and the interaction among objects.
NOTE 2: For each sequence diagram, you can use one Actor, one UI, one Application server, and as many as you need Data server for top-level ‘objects’ (like the example I will share with you).
NOTE 3: Before submission, ensure you have labeled all the messages and used the right message types.
Necessary material will be given.
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Lucid Sequence Diagram Template
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