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OK, I think I get it. There is no good reason for rigidly ordering these
elements, we've just run into a limitation of the XML Schema standard.

On Fri, Aug 1, 2008 at 6:55 AM, Ray Denenberg, Library of Congress <
[log in to unmask]> wrote:

> <cartographics> is defined as xsd:sequence because <scale> and
>  <projection>
> are not repeatable, but <coordinates>  is repeatable.
>
> <all> requires that each element occur zero or one time and would not allow
> multiple <coordinates> elements.
>
> <choice maxOccurs="unbounded"> (which MODS uses in cases without such
> constraints)  would not constrain <scale> and <projection> to maximum one
> occurence.
>
> (Contrast this for example with <subject> ........
>
> <choice maxOccurs="unbounded">
> <element name="topic"/>
> <element name="geographic"/>
> <element name="temporal"/>
> <element name="titleInfo"/>
>
> etc.
>
> </choice>
>
> etc.
>
> .....any of these subject categories may occur any number of times,
> including zero, and the whole set may occur in any order.)
>
>
> ----- Original Message -----
> From: "Joe Altimus" <[log in to unmask]>
> To: <[log in to unmask]>
> Sent: Thursday, July 31, 2008 5:30 PM
> Subject: [MODS] schema use of xsd:sequence to define children of the
> cartographics element
>
>
> I notice that the MODS schema uses xsd:sequence to define the children
> of the cartographics element:
>
>        <xsd:sequence>
>               <xsd:element name="scale" minOccurs="0" type="xsd:string"/>
>               <xsd:element name="projection" minOccurs="0"
> type="xsd:string"/>
>               <xsd:element name="coordinates" minOccurs="0"
> maxOccurs="unbounded" type="xsd:string"/>
>        </xsd:sequence>
>
> However, an example of <cartographics> in the MODS User Guidelines
> does not conform to the schema:
>
> <subject>
>  <cartographics>
>    <coordinates>E 72--E 148/N 13--N 18</coordinates>
>    <scale>1:22,000,000</scale>
>    <projection>Conic proj</projection>
>  </cartographics>
> </subject>
>
> so I wonder if the example is wrong or the Schema (xsd:all instead of
> xsd:sequence)? Is there a strong reason why the children should occur
> in a rigid order in this case?
>
> Joe Altimus
> Arizona State University Libraries
>