From W3C Wiki
Co-Constraint Dimension: Effect
In message Analysis of use cases for co-constraints Fabio Vitali proposed a set of dimensions for the evaluation of co-constraints use cases. This is an explanation of dimension effect.
Effect: the kind of effect the dependency has on the destination
- FLAG: Just raise a validation error
- UPGRADE: Optional structure becomes required, nillable structure becomes non-nil
- DOWNGRADE: Optional structure must not appear, nillable structure becomes nil
- MUTUAL PRESENCE: both structures must appear together or none
- MUTUAL EXCLUSION: either structure must appear, but not both. None appearing is acceptable
- ALTERNATIVE EXCLUSION: either structure must appear, but not both. One must appear.
- RESTRICTION: a normally acceptable structure is not acceptable
- RELAXATION: a normally unacceptable structure is acceptable
- CHOICE OF TYPE: one of multiple content models is chosen
- NOT CLEAR: use case does not explain the effect