From what I can find, neither the DFDL spec, nor the errata seem to make it clear that when using lengthKind='pattern' if there is no match to the lengthPattern regex, it is NOT a processing error, but rather just results in length 0.

We need to clarify this. -- Mike Beckerle | OGF DFDL Workgroup Co-Chair | Tresys Technology | www.tresys.com