In a UML diagram, when should a class be abstract?

Question

In a UML diagram, when should a class be abstract? Just when do we want to prevent instantiation?

Edit: Can an abstract class fully implement a method (when the method depends only on the attributes of this abstract class)?

Answer 1

Preventing instantiation is an implementation issue, so this is a good reason if you are thinking of Java, C #, etc.

However, at the modeling level, you want to make an abstraction of the class if there are several subclasses, and it makes no sense that the object has a supertype, but not one of the subtypes.

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Answer 7

and an abstract class means that you can maintain a list of methods or variables (open static final by default inside an abstract class), this imposes a class that extends this abstract class to implement methods that are not implemented in the declared abstract class (an abstract class has a large similarities to interfaces, but the only difference is that interfaces are 100% abstract classes).