RE: [xml-dev] XML schema - multiple import of module

["DUNN, Mark" <mark.dunn@oup.com>]

Thanks Michael,

Thanks also to George, with essentially the same solution, and to Lech
for suggesting NVDL.

Having two schemas that import each other still seems kind of circular,
but better than my rickety chain of imports, and XMLSpy allows it.

The reason for using xs:redefine was that I want a <p> in a 'main.xsd'
document to be allowed to contain certain other elements defined only in
main.xsd itself. 

The bigger picture is that we have a 'core' set of structural elements
(paragraphs, titles, typographic elements, etc.) included in various
other DTDs (for legal documents, chapter-based books, A-Z reference,
etc.). I need the model of <p> (from the core set) to be slightly
different in each of the including DTDs, and am looking for a way of
expressing this in XML Schema.

I chose the xs:redefine element because it corresponded to the way the
old DTD was defined.

Maybe I need to have a separate <p> element in the including schemas, in
a separate namespace from the core <p> element, and extending its model.

Thanks again for all the suggestions!

Regards,

Mark



-----Original Message-----
From: Michael Kay [mailto:mike@saxonica.com] 
Sent: 04 June 2009 18:32
To: DUNN, Mark; xml-dev@lists.xml.org
Subject: RE: [xml-dev] XML schema - multiple import of module

Unfortunately the topic of schema composition is one where the spec
isn't
all that prescriptive, and where in consequence there are differences
between implementations.

Having said that, I can't see why you have three schema documents or why
you
are trying to use xs:redefine.

You should have two schema documents, one for each namespace, and each
should reference the other using an xsl:import. If your chosen tool
doesn't
allow that, I can only suggest you try a different tool.

Regards,

Michael Kay
http://www.saxonica.com/
http://twitter.com/michaelhkay  

> -----Original Message-----
> From: DUNN, Mark [mailto:mark.dunn@oup.com] 
> Sent: 04 June 2009 17:35
> To: xml-dev@lists.xml.org
> Subject: [xml-dev] XML schema - multiple import of module
> 
> Hello,
> 
> I'm new to XML Schemas, and investigating conversion of a DTD 
> to an XML Schema. I have a problem describing the Schema 
> version of the following
> structure:
> 
> <doc>
>  <div>
>   <title>Section 1</title>
>   <p>Some text...</p>
>   <p>
>    <law:extraxt>
>     <title>Title of Regulation</title>
>     <p>Text of regulation</p>
>    </law:extract>
>   </p>
>  </div>
> </doc>
> 
> 
> The problem is in the non-namespaced <title> and <p> elements 
> occurring within the namespaced <law:extract> element. They 
> are the same as the ones occurring outside this element, so 
> I'd like to define them only once.
> 
> My attempt at expressing this structure uses three .xsd files:
> 
> main.xsd:
> 
> <xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema";
> xmlns="http://xsd.oup.com/ac-xsd/";
> xmlns:law="http://xsd.oup.com/ac-law/";
> targetNamespace="http://xsd.oup.com/ac-xsd/";
> elementFormDefault="qualified">
> 	<xs:redefine schemaLocation="struct.xsd">
> 		<xs:group name="paragraph-content">
> 			<xs:choice>
> 				<xs:group ref="paragraph-content"/>
> 				<xs:element ref="law:extract"/>
> 			</xs:choice>
> 		</xs:group>
> 	</xs:redefine>
> 	<xs:import namespace="http://xsd.oup.com/ac-law/";
> schemaLocation="law.xsd"></xs:import>
> 	...
> </xs:schema>
> 
> law.xsd:
> 
> <xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema";
> elementFormDefault="qualified"
> targetNamespace="http://xsd.oup.com/ac-law/";
> xmlns:law="http://xsd.oup.com/ac-law/";
> xmlns:struct="http://xsd.oup.com/ac-xsd/";>
> 	<xs:import schemaLocation="struct.xsd"
> namespace="http://xsd.oup.com/ac-xsd/";></xs:import>
> 	<xs:element name="extract">
> 		<xs:complexType>
> 			<xs:sequence>
> 				<xs:element ref="struct:title"
> minOccurs="0"/>
> 				<xs:element ref="struct:p"
> minOccurs="1"/>
> 			</xs:sequence>
> 		</xs:complexType>
> 	</xs:element>
> 	...
> </xs:schema> 
> 
> 
> struct.xsd:
> 
> <xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema";
> elementFormDefault="qualified" attributeFormDefault="unqualified"
> targetNamespace="http://xsd.oup.com/ac-xsd/";
> xmlns="http://xsd.oup.com/ac-xsd/";>
> 	<xs:group name="general-inline">
> 		<xs:choice>
> 			<xs:element ref="b"/>
> 			<xs:element ref="i"/>
> 		</xs:choice>
> 	</xs:group>
> 	<xs:group name="paragraph-content">
> 		<xs:choice>
> 			<xs:group ref="general-inline"></xs:group>
> 			<!-- ... [plus others] ... --->
> 		</xs:choice>
> 	</xs:group>
> 	<xs:element name="p">
> 		<xs:complexType mixed="true">
> 			<xs:choice minOccurs="0" maxOccurs="unbounded">
> 				<xs:group ref="paragraph-content"/>
> 			</xs:choice>
> 		</xs:complexType>
> 	</xs:element>
> 	...
> </xs:schema>
> 
> 
> When I try saving the schema files in XMLSpy 2009, I get an 
> error saying that <title> is already declared, presumably 
> because the file struct.xsd has ben imported twice.
> 
> The W3C spec says that importing twice is legitimate, but 
> vendors are encouraged to raise it as an error. Fair enough - 
> I don't like the circularity in my description.
> 
> But the structure itself seems reasonable, I just can't see a 
> way of expressing it in XML Schema.
> 
> Can anyone help?
> 
> 
> Kind regards,
> 
> Mark Dunn
> XML Data Engineer
> Oxford University Press
> 
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This message is confidential. You should not copy it or disclose its contents to anyone. You may use and apply the information for the intended purpose only. OUP does not accept legal responsibility for the contents of this message. Any views or opinions presented are those of the author only and not of OUP. If this email has come to you in error, please delete it, along with any attachments. Please note that OUP may intercept incoming and outgoing email communications.