Fixed property in length facet is redundant

    Hi,
I'm writing own XML Schema part 2 Datatypes validator. But I'm confused 
because of "length" facet.

It's got a property "fixed". In REC it is said:

If <http://www.w3.org/TR/xmlschema-2/#length-fixed>{fixed} is true, then 
types for which the current type is the 
<http://www.w3.org/TR/xmlschema-2/#defn-basetype>{base type definition} 
cannot specify a value for 
<http://www.w3.org/TR/xmlschema-2/#dc-length>length other than 
<http://www.w3.org/TR/xmlschema-2/#length-value>{value}.

But then one constraint says:
Schema Component Constraint: length valid restriction
It is an 
<http://www.w3.org/TR/xmlschema-2/#dt-error>·error<http://www.w3.org/TR/xmlschema-2/#dt-error>· 
if <http://www.w3.org/TR/xmlschema-2/#dc-length>length is among the members 
of <http://www.w3.org/TR/xmlschema-2/#defn-facets>{facets} of 
<http://www.w3.org/TR/xmlschema-2/#defn-basetype>{base type definition} and 
<http://www.w3.org/TR/xmlschema-2/#length-value>{value} is not equal to the 
<http://www.w3.org/TR/xmlschema-2/#length-value>{value} of the parent 
<http://www.w3.org/TR/xmlschema-2/#dc-length>length.

It seems like redundance? Or is there any difference?

    Thanks, Tobbi