a. Update the protocol document to refer to "Core.ModificationException", or b. Update the Core.Vocabulary to prefix "Data" to "ModificationException", "ModificationExceptionType", and "ModificationOperationKind" I kinda prefer the prefixed name (b), although it is slightly longer. However, the vocabulary changes are "live" where-as the protocol document has not yet been finalized, so b) would technically be a breaking change to anyone using the new vocabulary term, although it could be argued that it's unlikely that people are already using that term.