3.B] Illustrate Scenario Based Modeling with Safe Home Surveillance example.
Answer:
Scenario-based modeling involves creating and analyzing scenarios to understand and document how users interact with a system. Here’s how it applies to the SafeHome surveillance system:
SafeHome Surveillance Example
1. Use Case Development:
- Use Case: Access Camera Surveillance via the Internet – Display Camera Views (ACS-DCV)
- Actor: Homeowner
- Goal in Context: To view camera output from any remote location via the Internet.
Scenario:
- Log in: Homeowner accesses the SafeHome Products website.
- Authenticate: Enters user ID and passwords.
- Access Functionality: Selects “surveillance” from the major function buttons.
- Pick Camera: Chooses “pick a camera,” displaying the house floor plan.
- View Camera: Selects a camera from the floor plan and clicks “view” to see video output in a window.
2. Refining the Use Case:
- Primary Scenario: Details the basic steps for the homeowner to view a camera feed.
- Secondary Scenarios:
- Thumbnail View: Homeowner can opt to view thumbnail snapshots from all cameras.
- Error Handling: If no floor plan is configured, an error message is shown.
- Alarm Condition: If an alarm condition occurs, a separate use case manages the alarm.
3. Formal Use Case Template:
- Use Case: Access Camera Surveillance via the Internet – Display Camera Views (ACS-DCV)
- Preconditions: System must be configured; valid user ID and passwords required.
- Trigger: Homeowner wants to check the house remotely.
- Scenario: Steps from logging in to viewing a specific camera feed.
- Exceptions: Incorrect credentials, system not configured, missing floor plan, etc.
- Priority: Moderate, to be implemented after basic functions.
- Frequency of Use: Moderate.
4. Use Case Diagram:
- Actors: Homeowner, Cameras
- Use Cases: Access camera surveillance, Configure SafeHome system parameters, Set alarm.
- Diagram:
- Actors are represented outside the system boundary.
- Use Cases are ovals inside the system boundary.
