The Use-case model is defined as a model which is used to show how users interact with the system in order to solve a problem. As such, the use case model defines the user's objective, the interactions between the system and the user, and the system's behavior required to meet these objectives.Various model elements are contained in use-case model, such as actors, use cases, and the association between them.
The formal functional requirements of things that a Use Case must provide to the end user, such as <ability to update order>. These correspond to the functional specifications found in structured methodologies, and form a contract that the Use Case performs some action or provides some value to the system.
Formal, sequential descriptions of the steps taken to carry out the use case, or the flow of events that occur during a Use Case instance. These can include multiple scenarios, to cater for exceptional circumstances and alternative processing paths. These are usually created in text and correspond to a textual representation of the Sequence Diagram.
Sequence diagrams to depict the workflow; similar to Scenarios but graphically portrayed.
Use Cases are typically related to 'actors', which are human or machine entities that use or interact with the system to perform a piece of meaningful work that helps them to achieve a goal. The set of Use Cases an actor has access to defines their overall role in the system and the scope of their action.
Sequence diagrams provide a graphical representation of object interactions over time. These typically show a user or actor, and the objects and components they interact with in the execution of a use case. One sequence diagram typically represents a single Use Case 'scenario' or flow of events.
Sequence diagrams are an excellent way of documenting usage scenarios and both capturing required objects early in analysis and verifying object use later in design. The diagrams show the flow of messages from one object to another, and as such correspond to the methods and events supported by a class/object.
A model element used to structure the use case model to simplify analysis, communications, navigation, and planning. If there are many use cases or actors, you can use use-case packages to further structure the use-case model in much the same manner you use folders or directories to structure the information on your hard-disk.
You can partition a use-case model into use-case packages for several reasons, including:
· To reflect the order, configuration, or delivery units in the finished system thus supporting iteration planning.
· To support parallel development by dividing the problem into bite-sized pieces.