use cases Flashcards
what are use cases often used for
to derive functional requirements
what is the best way to discover requirements and what are some limitations
talking to stakeholders
they may express them in their own terms
the can change their minds
system developers may make assumptions
what is a use case
a behavioural model of a system
also a standard part of uml
what do use cases consist of
use case diagram and description
what are some positives of use cases (4)
graphical
you describe sample scenarios which are easy to discuss with the user
easy way to communicate between different stakeholders
used to derive test cases
how are use cases represented in the model
ovals
what does the box in a use case model represent
system boundaries
how is a use case written
a verb noun phrase that represents where the system would be used
actor
a user system or device that interacts with the system
use case description
a sequence of steps that identifies what you need to do to complete a use case
primary actor
the actor that wants to achieve the use case
secondary actor
interacts with the use case in order to help the primary actor complete it
precondition
activities that must take place before the use case can start
flow of events
user actions and system responses that take place under the regular execution of the use case
alternate flows
you must complete another task before going back to the flow of events
post conditions
the state of the system when the use case has been completed
why do we not use control statements and what do we use instead
it can make our description too algorithmic so we use scenarios instead
primary scenario
what we expect to be normal behaviour
secondary scenarios
reveal useful information e.g. exceptions
«include»
adds one use case’s behaviour into another when it is mandatory
«extend»
adds optional/conditional behaviour to another use case
exceptions
scenarios where the postcondition cannot be fulfilled
alternatives
different ways to fulfil the post conditions
what are the 4 levels of use case detail
cloud level
sea level
fish level
bottom-of-the-ocean level
