High level description of an actual problem a user (of an [[API]]) may face. For example:

''I want to alphabetically sort names of some persons''

Such [[usecase]] is then states that this is a problem that this [[API]] is ready to solve and is then followed by a ''scenario'' how to solve the given problem. For example:

''Create a List of Strings. Put there the names. Use sort method.''

Which is then reflected by the actual realization. In [[Java]]:

<source lang="java">
List<String> arr = new ArrayList<String>();
arr.add("Tom");
arr.add("Petr");
Collections.sort(arr);
</source>

[[Usecase]] are an important entry point when describing and documenting [[API]] [[DocumentDeclarativeAPI|abstractions]].