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Quality Attributes

Quality attributes are the non-functional requirements that define the overall quality of the system and how it delivers its functionalities.

Quality Attributes Overview​

Operational Properties​

  1. Availability:
    • Fault tolerance: The system should be able to recover from failures and continue to operate.
  2. Reliability:
    • Error handling: The system should be able to handle errors gracefully.
    • Data integrity: The system should ensure that data is consistent and accurate.
  3. Deployability:
    • Portability: The system should be able to run on different platforms.
    • Upgradability: The system should automatically deploy new versions.

Structural Properties​

  1. Modifiability:
    • Extensibility: The system should be able to add new features easily.
    • Maintainability: The system should be easy to maintain and update.
  2. Testability:
    • Observability: The system should be able to provide information about its internal state.
    • Controllability: The system should be able to be controlled during testing.
  3. Security:
    • Authentication: The system should be able to authenticate users.
    • Authorization: The system should be able to authorize users to access resources.
    • Data protection: The system should protect sensitive data.
  4. Usability:
    • Learnability: The system should be easy to learn.
    • Efficiency: The system should be efficient to use.
    • Satisfaction: The system should be satisfying to use.

Scenarios​

For some quality attributes, we have defined scenarios to illustrate how they will be achieved.

Availability​

Scenario 1: Fault Tolerance​

  • Stimulus Source: Hardware failure.
  • Stimulus: A server node fails.
  • Environment: Normal operation.
  • Artifact: Server node.
  • Response: The system detects the failure and restarts the server node.

Reliability​

Scenario 1: Error Handling​

  • Stimulus Source: User action.
  • Stimulus: User enters invalid data.
  • Environment: Normal operation.
  • Artifact: System.
  • Response: The system displays an error message to the user.

Scenario 2: Data Integrity​

  • Stimulus Source: User action.
  • Stimulus: User updates their profile.
  • Environment: Normal operation.
  • Artifact: System.
  • Response: The system updates the user's profile without data loss.

Deployability​

Scenario 1: Portability​

  • Stimulus Source: Deployment.
  • Stimulus: Deploy the system on a new platform.
  • Environment: Normal operation.
  • Artifact: System.
  • Response: The system runs on the new platform without modification.

Scenario 2: Upgradability​

  • Stimulus Source: Deployment.
  • Stimulus: Deploy a new version of the system.
  • Environment: Normal operation.
  • Artifact: System.
  • Response: The system automatically deploys the new version.

Modifiability​

Scenario 1: Extensibility​

  • Stimulus Source: New feature request.
  • Stimulus: Add a new feature to the system.
  • Environment: Normal operation.
  • Artifact: System.
  • Response: The new feature is added to the system without affecting existing features.

Scenario 2: Maintainability​

  • Stimulus Source: Bug report.
  • Stimulus: Fix a bug in the system.
  • Environment: Normal operation.
  • Artifact: System.
  • Response: The bug is fixed without introducing new bugs.

Testability​

Scenario 1: Observability​

  • Stimulus Source: Testing.
  • Stimulus: Monitor the system during testing.
  • Environment: Testing.
  • Artifact: System.
  • Response: The system provides information about its internal state.

Scenario 2: Controllability​

  • Stimulus Source: Testing.
  • Stimulus: Control the system during testing.
  • Environment: Testing.
  • Artifact: System.
  • Response: The system can be controlled during testing.

Security​

Scenario 1: Authentication​

  • Stimulus Source: User action.
  • Stimulus: User logs in to the system.
  • Environment: Normal operation.
  • Artifact: System.
  • Response: The system authenticates the user.

Scenario 2: Authorization​

  • Stimulus Source: User action.
  • Stimulus: User accesses a protected resource.
  • Environment: Normal operation.
  • Artifact: System.
  • Response: The system authorizes the user to access the resource.

Scenario 3: Data Protection​

  • Stimulus Source: User action.
  • Stimulus: User enters sensitive data.
  • Environment: Normal operation.
  • Artifact: System.
  • Response: The system encrypts the sensitive data.

Usability​

Scenario 1: Learnability​

  • Stimulus Source: User action.
  • Stimulus: User interacts with the system for the first time.
  • Environment: Normal operation.
  • Artifact: System.
  • Response: The user quickly learns how to use the system.

Scenario 2: Efficiency​

  • Stimulus Source: User action.
  • Stimulus: User performs a task.
  • Environment: Normal operation.
  • Artifact: System.
  • Response: The system allows the user to perform the task quickly.

Scenario 3: Satisfaction​

  • Stimulus Source: User action.
  • Stimulus: User interacts with the system.
  • Environment: Normal operation.
  • Artifact: System.
  • Response: The user enjoys using the system.