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Re: Is it correct schema definition?

• To: "Li Yuejiong(John)" <john_li@m...>
• Subject: Re: Is it correct schema definition?
• From: ht@i... (Henry S. Thompson)
• Date: Mon, 05 Dec 2005 17:25:17 +0000
• Cc: <xml-dev@l...>
• In-reply-to: <EDBEE001298F534EBCFEE2C1B4FAC86D9B8F89@m...> (LiYuejiong's message of "Mon, 5 Dec 2005 22:26:11 +0800")
• References: <EDBEE001298F534EBCFEE2C1B4FAC86D9B8F89@m...>
• User-agent: Gnus/5.1007 (Gnus v5.10.7) XEmacs/21.4.17 (Jumbo Shrimp, linux)

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Li Yuejiong(John) writes:

> The following piece of schema is from a released Schema definition.The
> problem is the attribute "fixed". In the element definition, fixed="" is
> correct or not?
>
>   <complexType name="countryItemType">
>     <simpleContent>
>       <restriction base="stringItemType">
>         <length value="0" fixed="true" />

In this case, 'fixed' means that no further restriction is allowed by
subsequent restrictions (actually pointless here, since 0 is as low as
you can go, but perfectly legal).

>       </restriction>
>     </simpleContent>
>   </complexType>
>
>   <element id="id_Afghanistan" name="Afghanistan" type="countryItemType"
> substitutionGroup="CountryItemHead" fixed="" nillable="true" />

In this case the 'fixed' attribute has the force that elements
validated with this declaration must always be empty.

Taken together this all overdoes it a bit, in that elements validated
by the above declaration must always be empty for two _distinct_
reasons, namely the 'fixed' on the elt decl and the restriction to
length 0 of its type.

Also, under the circumstances, 'nillable="true"' is pointless, as it
means elements validated by that decl _may_ be empty even if their
type doesn't allow that, but the type _does_ allow that, so . . .

ht
- -- 
 Henry S. Thompson, HCRC Language Technology Group, University of Edinburgh
                     Half-time member of W3C Team
    2 Buccleuch Place, Edinburgh EH8 9LW, SCOTLAND -- (44) 131 650-4440
            Fax: (44) 131 650-4587, e-mail: ht@i...
                   URL: http://www.ltg.ed.ac.uk/~ht/
[mail really from me _always_ has this .sig -- mail without it is forged spam]
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    • From: Kasimier Buchcik <K.Buchcik@4...>

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    • From: "Li Yuejiong(John)" <john_li@m...>

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