question about {attribute uses}

The {attribute uses} property of the attributeGroup schema definition
component is defined as:

"The union of the set of attribute uses corresponding to the <attribute>
[children], if any, with the {attribute uses} of the attribute groups ·
resolved· to by the ·actual value·s of the ref [attribute] of the
<attributeGroup> [children], if any."
                                                                                           
                                                                                           
 By definition, a "union" for a set has no duplicate members.     If the children of the   
 attribute group were the following:                                                       
                                                                                           
    <xs:attribute ref="bill"/>                                                             
    <xs:attribute ref="fred"/>                                                             
    <xs:attribute ref="bill"/>                                                             
                                                                                           
 does the {attribute uses} which results from the union contain 2 or 3 members?    (i.e.   
 does it contain 1 or 2 attribute uses for "bill")?                                        
                                                                                           
 I'm trying to determine whether the resulting set has duplicate attribute uses for        
 "bill", and whether we need to detect an error for this according to constraint 2 of      
 section 3.6.6 of Structures.                                                              
                                                                                           
                                                                                           
 Thx,                                                                                      
 Lisa.                                                                                     
                                                                                           
                                                                                           
                                                                                           
                                                                                           
                                                                                           

Received on Monday, 1 October 2001 15:51:32 UTC