The DFDL spec is very restrictive about the use of %ES; - it is only permitted as a nil literal value.  But the spec does not say anything about the use of %WSP*; when used on its own - which may equivalently be written as "%ES; %WSP+;". I don't think that  %WSP*; should be allowed on its own other than for nil literal value.  It may of course be used in combination with other DFDL entities.

Regards

Steve Hanson
Architect, Data Format Description Language (DFDL)
Co-Chair, OGF DFDL Working Group
IBM SWG, Hursley, UK
smh@uk.ibm.com
tel:+44-1962-815848
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