The DFDL Spec current disallows DFDL statement annotations (assert, discriminator, setVariable, newVariableInstance) to appear on global element declarations and on simpleTypes.

However, the DFDL Workgroup has agreed this is an oversight and needs to be corrected. A future draft of the specification will correct this, and an errata to the existing spec is forthcoming.

This features is needed to support important data formats in a reasonable way that avoids repetition of regular expressions all over the schema.