+-- | Type representing different validation errors.
+-- Only 'ParseError' and 'ValidatorError' are exported, @SigMismatch@ and
+-- @NoVerifier@ are used internally and should not be used by the user
+data ValidationError = SigMismatch -- ^ Signatures do not match
+ | NoVerifier -- ^ No verifier can handle a given caveat
+ | ParseError String -- ^ A verifier had a parse error
+ | ValidatorError String -- ^ A verifier failed
+ deriving (Show,Eq)