Relation type labels can be changed. With respect to the signature covariance new relations can also be added without consequences for existing knowledge.
For obvious reasons of referential integrity, the removal of a relation assumes that all occurrences have disappeared from all graphs, both in annotations and within ontology.
The consequences of the change of a signature depends on its nature: if the arity of the signature is changed, all occurrences of the relation will require user’s intervention; if only the concept types of the signature are changed, then it will be a different signature.
If a concept type is replaced by a more general type, the content of the knowledge base will not be affected, and no error will occur. However, if a term is specialized, it can have an effect on the content of the knowledge base, and can also trigger errors in the annotations. Removing a link between two relation types does not create inconsistencies in the database but can decrease the number of answers; adding a link can increase the number of answers (new rules may be applicable) and some constraints may become unsatisfied.

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