Check constraints can be used... <xsd:annotation> <xsd:appinfo source="http://www.ogf.org/dfdl/dfdl-1.0/"> <dfdl:assert test="{ dfdl:checkConstraints(.) }" message="There cannot be more than 59 seconds in a minute."/> </xsd:appinfo> </xsd:annotation> ...to validate (while parsing) the restrictions placed on an element: <xsd:simpleType> <xsd:restriction base="xsd:unsignedInt"> <xsd:maxInclusive value="59"/> </xsd:restriction> </xsd:simpleType> Is check constraints similarly required to validate the fixed value of an element while parsing? <xsd:element name="MimeVersion" dfdl:initiator="MIME-Version:%SP;" dfdl:terminator="%NL;" type="xsd:string" dfdl:length="3" dfdl:lengthKind="explicit" fixed="1.0"> If not, then how do I force it to validate while parsing? TIA