abstract operation

An operation that lacks an implementation—that is, one that has a specification but no method. An implementation must be supplied by any concrete descendant class.

See abstract, generalizable element, inheritance, polymorphic.

Semantics

If an operation is declared as abstract in a class, it lacks an implementation (a method or a trigger) in the class, and the class itself is necessarily abstract. An implementation must be supplied for the operation by a concrete descendant. If the class inherits an implementation of the operation but declares the operation as abstract, the abstract declaration invalidates the inherited implementation in the class. If an operation is declared as concrete in a class, then the class must supply ...

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