Which of the following includes acceptance criteria as part of its definition?

The correct choice is related to the concept of a user story, which is an integral part of Agile methodologies. In Agile development, a user story is a brief, simple description of a feature told from the perspective of the person who desires the new capability, typically a user or customer of the system.

Acceptance criteria are essential elements that accompany user stories to specify the conditions under which the story can be considered complete. They outline the expected outcomes and ensure that all stakeholders have a shared understanding of what needs to be achieved. This helps in validating whether the functionality delivered in the iteration meets the needs of the users and adheres to the desired quality standards. Acceptance criteria serve as the basis for acceptance testing and guide the development team throughout the implementation process.

The other options do not include acceptance criteria as part of their definition, focusing instead on different aspects. The user interface pertains to the specific elements through which users interact with the software, while user experience refers to the overall experience a user has while using a product, which encompasses usability but not specifically success criteria like acceptance criteria. The V-model is a software development paradigm that emphasizes planning and testing phases but does not incorporate acceptance criteria in the same direct way user stories do.