Use Case Diagram

Correct Answer: An optional behavior that enhances the base use case under specific conditions

An <> relationship in UML Use Case Diagrams represents additional, optional behavior that supplements a base use case under specific conditions. The correct answer best captures this concept by stating it's an optional behavior that enhances the base use case under specific conditions. This accurately describes how an extend relationship works in use case modeling. The other options are incorrect because: - A mandatory requirement before completion describes a <> relationship, not an <> relationship - An alternate path that replaces the main flow describes an alternative flow within a use case, not an extend relationship - A specialized version that inherits characteristics describes generalization/specialization relationships (shown with a solid line and hollow arrowhead), not an extend relationship

Correct Answer: An Inclusive (OR) relationship between two use cases

An inclusive (OR) relationship is the most appropriate representation for a secure login system offering both facial recognition and password authentication because: It accurately models a situation where users can choose either authentication method or potentially use both methods for enhanced security. The OR relationship indicates that at least one of the authentication methods must be used, but both can be utilized if desired. Other options are incorrect because: - A generalization relationship between actors would represent inheritance of characteristics, not authentication choices - Extension points are used for optional behavior that extends the basic flow, not for representing alternative authentication methods - An exclusive (XOR) relationship would force users to choose only one authentication method, preventing the possibility of using both methods for increased security

Correct Answer: Both actors can perform the use case independently

When two actors share the same relationship with a use case in a Use Case Diagram, both actors have the independent ability to perform that use case. This is a fundamental principle of UML Use Case modeling. Each actor represents a role that interacts with the system, and when multiple actors are connected to the same use case, each has their own independent relationship with that use case. They don't need to coordinate or collaborate unless explicitly specified through a different notation. The other answers are incorrect because: - Actors do not need to collaborate unless specifically shown with a different notation or relationship - There is no concept of priority or hierarchical access in standard use case relationships - There is no restriction on concurrent execution of use cases by different actors - multiple instances of the same use case can be performed simultaneously by different actors