derivation by restriction and the use attribute

["Helmut Dirtinger" <helmut_dirtinger@hotmail.com>]

Hi

 

I am currently experimenting with derivation by restriction and attribute declarations. I tried all combinations of changing the attribute use="required|prohibited|optional" from the base type to the derivation. The following two combinations of are intuitively valid.

 

(1)Basetype: use="optional" Subtype:use="prohibited"
(2)Basetype: use="optional" Subtype:use="required"

 

These combinations seem to be a clear restriction of an attributes cardinality from (0,1) to (0,0) in case 1 and to (1,1) in case 2.

As the XML Schema specification is quite complex I rely on XSV and IBMs Schema Quality Checker to find out the valid combinations.

XSV doesn't bother about changing the attribute through derivation by restriction - all combinations are valid.

SQC grants three combinations: case 1 and 2 and a third one:

 

(3) Basetype: use="required" Subtype:use="prohibited"

 

This case is not restriction. (In my understanding of a restriction)

 

So my question concerns the validity of this third case. Is this case valid? Where is it specified in the Schema Specification?

 

thx

 

Helmut Dirtinger