Designation of a model that is incorrectly constructed, one that violates one or more predefined or model-specified rules or constraints. Antonym: well formed.
See also conflict, constraint.
A model that violates well-formedness rules and constraints is not a valid model and therefore has inconsistent semantics. To attempt to use such a model may yield meaningless results. It is the responsibility of a modeling tool to detect ill-formed models and prevent their use in situations that might be troublesome. Because the use of some constructs extends the built-in UML semantics, automatic verification may not be possible in all cases. Also, automatic checking cannot be expected to verify consistency of operations, because that ...