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

[Richard Tobin <richard@cogsci.ed.ac.uk>]

In article <001501c23df1$c96f9160$6401a8c0@pcukmka> you write:


>> <xs:simpleType name="myEnum">
>>     <xs:union>
>>         <xs:simpleType>
>>             <xs:restriction base="xs:NMTOKEN">
...
>>         <xs:simpleType>
>>             <xs:restriction base="xs:string">
>>                 <xs:enumeration value=""/>
...

>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=""/>
...

It probably makes no difference to most users, but in the first case
the PSVI will reflect the fact that the value is an NMTOKEN if it is
(the memberTypeDefinition will be a subtype of xs:NMTOKEN).

-- Richard