RE: [xml-dev] XML Schema - Enumerated List to Allow Blank Value

From
Michael Kay <>
To
'Eddie Robertsson' <>, "'CHIUSANO, Joseph'" <>
Date
2002-08-07T09:06:59Z
ID
<001501c23df1$c96f9160$6401a8c0@pcukmka>
Thread
RE: [xml-dev] XML Schema - Enumerated List to Allow Blank Value
> ... However, you can easily to this by creating a union of 
> one enumerated xs:NMTOKEN type and one empty xs:string type. 
> Here is an 
> example:
> 
> <xs:simpleType name="myEnum">
>     <xs:union>
>         <xs:simpleType>
>             <xs:restriction base="xs:NMTOKEN">
>                 <xs:enumeration value="A"/>
>                 <xs:enumeration value="B"/>
>                 <xs:enumeration value="C"/>
>             </xs:restriction>
>         </xs:simpleType>
>         <xs:simpleType>
>             <xs:restriction base="xs:string">
>                 <xs:enumeration value=""/>
>             </xs:restriction>
>         </xs:simpleType>
>     </xs:union>
> </xs:simpleType>
> 
Why is this preferred to the more direct:

> <xs:simpleType name="myEnum">
>         <xs:simpleType>
>             <xs:restriction base="xs:string">
>                 <xs:enumeration value="A"/>
>                 <xs:enumeration value="B"/>
>                 <xs:enumeration value="C"/>
>                 <xs:enumeration value=""/>
>             </xs:restriction>
>         </xs:simpleType>
> </xs:simpleType>

?
Michael Kay
Software AG
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