Lab Exercise-2
Title: To study about the Activity and System Sequence diagram in UML.
Aim: To know the Activity and System Sequence diagram and give an
example of Ticket Vending Machine and Library Management System.
Description:
Unlike Use case, Activity and System Sequence Diagram are drawn from
elaboration phase of UML. Certainly! Let's delve into both Activity Diagrams
and System Sequence Diagrams (SSD) in UML (Unified Modeling
Language).
A. Activity Diagram
Purpose:
- To represent the flow of activities or tasks in a system or process.
- Used for modeling the workflow and operations in a system.
Key Elements:
1. Activities: Represented by rounded rectangles, these are the tasks or
operations that occur in the workflow.
2. Transitions: Arrows that show the flow from one activity to the next.
3. Decision Nodes: Represented by diamonds, used to show branching points
where the flow can go in different directions based on conditions.
4. Start (Initial) Node: Represented by a filled black circle, it indicates the
starting point of the diagram.
5. End (Final) Node: Represented by a filled black circle with a border, it
indicates the end point of the diagram.
6. Forks and Joins: Used for parallel processing, forks (a thick bar with one
incoming flow and multiple outgoing flows) split a single activity into
multiple parallel activities, and joins (a thick bar with multiple incoming
flows and one outgoing flow) merge them back into a single flow.
Example of Activity Diagram:
An activity diagram for a simplified online shopping process might include
activities such as "Browse Items," "Select Item," "Add to Cart," "Checkout,"
"Enter Shipping Information," and "Confirm Order."
B. System Sequence Diagram (SSD)
Purpose:
- To illustrate the sequence of interactions between external actors and the
system for a specific use case.
- Focuses on the high-level flow of events without going into the detailed
design of the system components.
Key Elements:
1. Actors: Represented by stick figures, these are the entities outside the
system that interact with it (e.g., users, external systems).
2. System: Represented by a rectangle, it encompasses the system or
application being modeled.
3. Messages: Arrows that show the interaction between actors and the system.
These can include method calls, events, or data flows.
4. Lifelines: Vertical dashed lines that represent the existence of an object or
actor over time.
5. Activation Bars: Thin rectangles on a lifeline that indicate when an object
is performing an action or sending a message.
Example of SSD:
An SSD for a use case like "Place Order" might include interactions such as:
- User sends a "Select Item" message to the system.
- System sends an "Add to Cart" message.
- User sends a "Proceed to Checkout" message.
- System sends a "Request Payment Information" message.
- User sends "Provide Payment Information" message.
- System sends "Confirm Order" message.
C. Differences and Uses
- Activity Diagrams are best used for modeling workflows and processes
within a system, showing the sequence and conditions for operations.
- System Sequence Diagrams are ideal for capturing the interaction between
external actors and the system for specific use cases, focusing on the flow of
events and messages.
By using both diagrams, you can gain a comprehensive understanding of both
the internal processes (Activity Diagram) and the external interactions (SSD)
of a system.
Task-1: Activity Diagram of Ticket Vending Machine and Library
Management System (LMS).
Fig: Activity Diagram of Ticket Vending Machine
Fig: Activity Diagram of Library Management System
Task-2: System Sequence Diagram(SSD) for Borrowing the book from
Library.
Fig: System Sequence Diagram for borrowing book from library.
Conclusion: We understand about Activity and System Sequence Diagram
(SSD)and completed above task in Draw.io .
