According to requirement DFDL-12-006R: If dfdl:trailingSkip is specified when dfdl:lengthKind is 'delimited' or 'endOfParent' then a dfdl:terminator must be specified.

I found this requirement when I was trying to figure out how daffodil would handle a delimited-length element with a trailingSkip and no terminator. Currently, this situation is not detected and I'm still trying to figure out exactly what is happening in my test. I'd assume that this should result in a Schema Definition Error.