Version: 1.3.0 (using KDE KDE 3.2.2) Installed from: Compiled From Sources OS: Linux When creating an abstract operation in a class, this class must be set to abstract as well, since a class with any number of abstract methods must be abstract. This can be done manually, but the actual behaviour breaks the UML standard.
Note that the opposite is not true: The fact that no operation is abstract does not imply that the class must be non-abstract. In practice this means that setting an operation to abstract will change the class to be abstract, but removing the abstractness from the operation will not remove the class' abstractness - that must be done manually.