Use Cases. Your System at a Glance.

What is a use case, what is it used for and what benefits are offered by use case diagrams?

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Use case example
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Use case diagrams show visible behaviour of a system as well as the scenarios in which the system interacts with persons or neighbouring systems.

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Actors are persons or systems outside of the system to be described, e.g. users, customers or processes.

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A use case is a scenario that describes the interaction of an actor with a system. It is also a description of what can happen during the process of target achievement.

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An extend relationship comprises two use cases one of which includes the other.

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If a use case extends another use case the stereotype extend is used. An extend relationship is expressed by a dashed line with an arrow.

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The result of a use case can be either success or failure/abortion.

What are Use Cases?

Use Cases document the functionality of a planned or existing system using simple models. A use case describes the visible behavior of a system from the user’s point of view. A user may be a person or a neighboring system and is knows as an actor; he or she interacts with the system in order to achieve a specific goal. A single use case gets its name from the goal the actor wants to achieve and is a series of actions performed in a defined order. Use cases are popular because they are relatively easy to set up and because they substantially increase the interaction between the actors and systems. They are often used in product and software development.

What are Use Cases used for?

Products or software are developed to help people perform tasks more efficiently. A user should be able to use the product in order to reach his or her goals. Very often these goals are not defined clearly. This could lead to delays in the development process and to higher costs. This happens when requirements have not been correctly elicited. In these cases changes need to be implemented, development processes need to be changed and resources have to be distributed differently. The later requirements become apparent the more problematic and expensive the development process will become. A use case bundles all the possible scenarios that could occur when attempting to achieve a goal. In that sense a use case result can be a success, but it can also be a failure or abortion.

Do you want to know what misuse cases are?  >>

How do I create use cases?

Two concepts that need to be implemented together form the basis of the use case approach:

Use case specifications contain information about how use cases interact with actors in an environment. The information is created with the help of templates, it is documented in text and should contain data points such as the: name (including identifier), description, participating actors, priority, criminality, responsibility, conditions, status, other use cases, standard and alternative procedures. Even conditions that are not subject to change, not even when an error has occurred, should be described.

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Sure, you could capture use cases with a pen and paper, but it’s much better to do so with software. Software offers you the big advantage of making several pieces of information related to use cases immediately available.

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The tabs in a form aid in the navigation. Users can orient themselves and find information easily. Below you can see the flow of steps as well as alternative steps.

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A standard procedure and an alternative flow (with poor Wi-Fi reception). Described step by step, optically and in an easy to understand way.

Use cases diagrams from UML (Unified Modeling Language) are graphical models that help you visualize the functionality of a system as well as their relationships with its environment. The important model elements include:

  • Use case
  • Actors (persons and systems)
  • System partitions
  • Relationships (extend, include and communicate)

The use case handbook as an ebook to take away.

Everything important to use cases, use case 2.0 and misuse cases at a glance.

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