Frederick,
Yes, Ed is right. Please use the attached xmldsig11-schema.rnc
instead.
Recently, ODF Part 3, which uses XML digital signature, has been
submitted for public review. Since there are no official RELAX NG
schemas for XML digital signature, their schemas allow anything
as digital signature.
I'm hoping that W3C publishes a technical note for RELAX NG schemas
for digital signature, the OASIS ODF TC uses them for ODF part 3,
and ISO/IEC/JTC1/SC34/WG4 uses them for OOXML Part 2.
Cheers,
Makoto