Topics: Use case, Use case diagram, Requirements analysis Pages: 15 (5214 words) Published: May 24, 2013

1. 1. Use-CASE:
In software and systems engineering, a use case is a list of steps, typically defining interactions between a role (known in UML as an "actor") and a system, to achieve a goal. The actor can be a human or an external system. In systems engineering, use cases are used at a higher level than within software engineering, often representing missions or stakeholder goals. The detailed requirements may then be captured in SysML or as contractual statements. Again a use case is a software and system engineering term that describes how a user uses a system to accomplish a particular goal. A use case acts as a software modeling technique that defines the features to be implemented and the resolution of any errors that may be encountered. A use case is a description of how users will perform tasks on your Web site/Devise/System. A use case includes two main parts:

* the steps a user will take to accomplish a particular task on system * the way the system should respond to a user's actions
A use case begins with a user's goal and ends when that goal is fulfilled. (Wikidipedia, 2013)

1. 2. Characteristics:

A use case (or set of use cases) has these characteristics:
* Organizes functional requirements
* Models the goals of system/actor (user) interactions
* Records paths (called scenarios) from trigger events to goals * Describes one main flow of events (also called a basic course of action), and possibly other ones, called exceptional flows of events (also called alternate courses of action) * Is multi-level, so that one use case can use the functionality of another one. Use cases can be employed during several stages of software development, such as planning system requirements, validating design, testing software, and creating an outline for online help and user manuals. (Rouse, 2007) |

1. 3. Coverage:
A use case describes a sequence of interactions between a user and a Web site, without specifying the user interface. Each use case captures:
* The actor (who is using the Web site/Device/System)
* The interaction (what does the user want to do?)
* The goal (what is the user's goal?)
1. 4. Steps:
The steps in designing use cases are:
* Identify the users of the system
* For each category of users, create a user profile. This includes all roles played by the users relevant to the system. * Identify significant goals associated with each role to support the system. The system’s value proposition identifies the significant role. * Create use cases for every goal associated with a use case template and maintain the same abstraction level throughout the use case. Higher level use case steps are treated as goals for the lower level. * Structure the use cases

* Review and validate the users
1. 5. Structure:
There is no standard way to write the content of a use case, and different formats work well in different cases. He describes "a common style to use" as follows: * Title: "goal the use case is trying to satisfy"

* Main Success Scenario: numbered list of steps
Step: "a simple statement of the interaction between the actor and a system" * Extensions: separately numbered lists, one per Extension[ * Fully dressed use case structure
Fully dressed use case template lists the following fields:
* Title: "an active-verb goal phrase that names the goal of the primary actor * Primary Actor
* Goal in Context
* Scope
* Level
* Stakeholders and Interests
* Precondition
* Minimal Guarantees
* Success Guarantees
* Trigger
* Main Success Scenario
* Extensions
* Technology & Data Variations List
* Related Information.
In addition, Cockburn suggests using two devices to indicate the nature of each use case: icons for design scope and goal level. * Variation scenarios "(maybe branching off from and maybe returning to the main scenario)" * Casual use case...
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