Introduction

Sequence diagrams are a design tool for modeling the dynamic interaction between elements in a software system. They can be used at different levels of abstraction, but are most often used for modeling interactions at the object to object and method call level. Without an understanding of these dynamic interactions, you do not really know how the software works. Modeling system features and operations with sequence diagrams provide this information as both a design and documentation tool.

Learning Outcomes

• Describe the UML notations used in sequence diagrams.
• Explain the role that sequence diagrams have in design modeling.
• Model the dynamic interactions for a software system feature using a sequence diagram.

Study Resources

For your study of this topic, use these resources.

Video Lessons

• Basics of a Sequence Diagram (1:38), from iOS Development: Architecture
• UML 2 Sequence Diagrams (12:13), Derek Banas

Web Articles and Blogs

• IBM Developer Works: The Sequence Diagram
• Microsoft: UML Sequence Diagrams: Reference, UML Sequence Diagrams: Guidelines, good introductions to sequence diagrams that are not tightly tied to the Microsoft tools.
• Agile Modeling: UML 2 Sequence Diagrams: An Agile Introduction
• Drawing tool tutorials
• Lucidchart: Sequence Diagram Tutorial
• WebSequenceDiagrams.com, a tool that generates sequence diagrams with a hand-drawn look from text descriptions. It is not good for formal documentation.
• https://sequencediagram.org, a tool that generates sequence diagrams from markup text descriptions. It is not good for formal documentation. Fairly comprehensive.
  1. Sample GET sequence diagram image matching with our current architecture: Diagram with layers - no use of cache
  2. Sample GET sequence diagram image matching with our current architecture (assuming cache): Diagram with layers - using cache
  3. Useful Template (starter) of basic markup so you can use to get started when creating all the sequence diagrams for your project: Starter with layers

NOTE: As a team you must agree on ONE TOOL to be used for your project work on Sequence Diagrams to ensure consistency. Please be aware that not all tools above are inherently collaborative and you will need to coordinate and manage updates to avoid confusion and mishaps.

Wikipedia

• Sequence Diagram

Class Lecture

• Sequence Diagrams

Exercises

Before-Class Exercises

• Sequence diagram - quiz: After watching one of the video lessons given above, reading the IBM Developer Works and Microsoft web articles, answer the questions in the 5-minute quiz, Sequence diagrams, in the myCourses Quiz area before the time specified on the schedule for your course section.

In-Class Exercises

• Sequence diagram - team: Working in your project team, create a sequence diagram that captures the dynamic interaction for a Customer adding an need to their funding basket based on a user story in your term project:
• Start the sequence from the Angular application.
• By the time indicated on the schedule for your class section, submit the sequence diagram to the Sequence diagram - team myCourses Assignments folder.
• It will be acceptable to draw the diagram on a whiteboard and take a photo of it for your submission.
• If you prefer, you can use a drawing tool instead which has the advantage that you will have a diagram suitable for insertion into your final design documentation.
• If you have additional time, select a second feature to model for a bonus exercise point. A second diagram should be done using a drawing tool.

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