der Anwendungsfall – use case
A use case is used to capture the requirements of a system. It describes one way a particular actor interacts with the system to achieve a particular goal.
If you have a blogging site, this goal could be logging into the site, creating a post, or even posting a comment.
The use case should specify the what, but not the how. It should only mention its external behaviour that is visible. The implementation details should not be included.
The different users are usually called actors, and are represented by the stickmen in a use case diagram (das Anwendungsfalldiagramm). The image for this post shows an example of a use case diagram. I chose that instead of including a use case proper because a use case is textual.
Very often, human users are actors, but it is also possible that another system is an actor.
You would usually generate the positive flow use cases first. These are the main workflows of what happens when things go right.
Then, you handle the alternate flows. These are less common scenarios, such as when a user encounters an error, or a particular edge case.
For organisation, each use case is usually numbered with an ID. Each use case is given a descriptive name, usually in the form of verb + noun/object. Actors are also listed.
Then, the flow listed as a sequence of steps:
Here is a simple example, using the example of a blogging site, and following the use case diagram:
Use case ID: 01
Use case name: Create post
Description: The writer creates a new post.
The noun Anwendung comes from the verb anwenden, which comes from the prefix an + verb wenden. Wenden comes from Middle High German wenden, which was from Old High German wenten, Causative of winden and means literally winden machen(to coil, I think).
Fall was originally came from the idea of the rolling of dice, but influenced by Latin casus (French: cas; both meaning “case” in English). So it looks like it’s exactly the same word in German.
This is the 30th word (and thus post) in this series, and it will be the last… for now.
I’ll be taking a break from this series to try something new! New posts on Thursdays will resume in March.
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