In computing, a scenario (UK: /sɪˈnɑːrioʊ/, US: /səˈnɛərioʊ/; loaned from Italian scenario (pronounced [ʃeˈnaːrjo]), from Latin scena 'scene'[1]) is a narrative of foreseeable interactions of user roles (known in the Unified Modeling Language as 'actors') and the technical system, which usually includes computer hardware and software.
A scenario describes one way that a system is used, or is envisaged to be used, in the context of an activity in a defined time-frame.
They are typically produced by usability or marketing specialists, often working in concert with end users and developers.
Increasingly, scenarios are used directly to define the wanted behaviour of software: replacing or supplementing traditional functional requirements.
Alexander and Maiden[3] list the following types: Negative scenarios or misuse cases may be written to indicate likely threats which should be countered to ensure that systems have sufficient security, safety, and reliability.