Hi,

Just an observation..

It seems like the RelaxNG Validation functions [1] can be overloaded/abused to provide NVDL validation [2]
As in:
validate:rng-report("data.xml","test.nvdl")

/Andy

[1] http://docs.basex.org/wiki/Validation_Module#RelaxNG_Validation
[2] http://www.nvdl.org/
[3] https://github.com/BaseXdb/basex/blob/master/basex-core/src/main/java/org/basex/query/func/validate/ValidateRng.java