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Re: key constraint question

• To: Bill Riegel <BRiegel@l...>
• Subject: Re: key constraint question
• From: "Chiusano Joseph" <chiusano_joseph@b...>
• Date: Fri, 16 May 2003 13:11:20 -0400
• Cc: xml-dev@l...
• Organization: BAH
• References: <D44A54C298394F4E967EC8538B1E00F101BCC8F5@l...>

Bill,

What you are trying to do (enforce that there is at least one occurrence
of element TableB whose "relationship" attribute value is "needed")
cannot be done with W3C Schema. 

Someone will be along very shortly to describe how Schematron can
enforce this.

Kind Regards,
Joe Chiusano
Booz | Allen | Hamilton

Bill Riegel wrote:
> 
> I am trying to define a serialized Database to XML, via a XML Schema.
> 
> Problem
> 
> Table A has two relations two Table B. One is required the other is
> optional.
> 
> How do I define that the TableB with relationship="needed" is mandatory.
> 
> I can define a unique constraint under TableA that indicates that
> TableB/primaryKey be unique. This would prohibit someone defining
> Two TableB's with the same relationship, i.e. two needed or two optional.
> 
> But I do not know how to ensure there is a TableB with the relationship of
> "needed".
> 
> Instance Document:
> 
> <TableA xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
> xsi:noNamespaceSchemaLocation="TestSchema.xsd">
>   <primaryKey>xx</primaryKey>
>   <TableB relationship="needed">
>     <primaryKey>yy</primaryKey>
>   </TableB>
>   <TableB relationship="optional">
>     <primaryKey>yy</primaryKey>
>   </TableB>
> </TableA>
> 
> Schema Document
> 
> <?xml version="1.0" encoding="UTF-8"?>
> <xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema"
> elementFormDefault="qualified" attributeFormDefault="unqualified">
>   <xs:element name="TableA">
>     <xs:complexType>
>       <xs:sequence>
>         <xs:element name="primaryKey"/>
>         <xs:element name="TableB" type="TableB_Type" maxOccurs="2"/>
>       </xs:sequence>
>     </xs:complexType>
>   </xs:element>
>   <xs:complexType name="TableB_Type">
>      <xs:sequence>
>       <xs:element name="primaryKey" type="xs:string"/>
>     </xs:sequence>
>     <xs:attribute name="relationship">
>                 <xs:simpleType>
>                   <xs:restriction base="xs:token">
>                     <xs:pattern value="needed|optional"/>
>                   </xs:restriction>
>                 </xs:simpleType>
>     </xs:attribute>
>   </xs:complexType>
> </xs:schema>
> 
> Bill Riegel
> LandMark Graphics
> 713-839-3388
> 
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org:Booz | Allen | Hamilton;IT Digital Strategies Team
adr:;;8283 Greensboro Drive;McLean;VA;22012;
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